264 Gauge & Higgs Boson Particle Listings Axions (A~ and Other Very Light Bosons
where CA is the axion field. It is often convenient to define the I Axions (A~ and Other forl axion decay constant fa with this Lagrangian [6]. The QCD Very Light Bosons, Searches nonperturbative effect induces a potential for CA whose mini- AXIONS AND OTHER VERY LIGHT BOSONS mum is at CA = OefffA cancelling 0eft and solving the strong Written October 1997 by H. Murayama (University of Califor- CP problem. The mass of the axion is inversely proportional nia, Berkeley) Part I; April 1998 by G. Raffelt (Max-Planck to fA as Institute, Miinchen) Part II; and April 1998 by C. Hagmann, K. van Bibber (Lawrence Livermore National Laboratory), and L.J. m A = 0.62 x 10-3eV x (IOI~ . (3) Rosenberg (Massachusetts Institute of Technology) Part III. The original axion model [1,5] assumes fA ~ v, where This review is divided into three parts: v = (v~Gf) -1/2 = 247 GeV is the scale of the electroweak Part I (Theory) symmetry breaking, and has two Higgs doublets as minimal Part II (Astrophysical Constraints) ingredients. By requiring tree-level flavor conservation, the ax- Part III (Experimental Limits) ion mass and its couplings are completely fixed in terms of one AXIONS AND OTHER VERY LIGHT BOSONS, parameter (tan~): the ratio of the vacuum expectation values PART I (THEORY) of two Higgs fields. This model is excluded after extensive (by H. Murayama) experimental searches for such an axion [7]. Observation of a narrow-peak structure in positron spectra from heavy ion colli- In this section we list limits for very light neutral (pseudo) sions [8] suggested a particle of mass 1.8 MeV that decays into scalar bosons that couple weakly to stable matter. They arise e+e -. Variants of the original axion model, which keep fA ~ v, if there is a global continuous symmetry in the theory that but drop the constraints of tree-level flavor conservation, were is spontaneously broken in the vacuum. If the symmetry is proposed [9]. Extensive searches for this particle, A~ MeV), exact, it results in a massless Nambu-Goldstone (NG) bosom ended up with another negative result [10]. If there is a small explicit breaking of the symmetry, either The popular way to save the Peccei-Quinn idea is to already in the Lagrangian or due to quantum mechanical effects introduce a new scale fA >> v. Then the A ~ coupling becomes such as anomalies, the would-be NG boson acquires a finite weaker, thus one can easily avoid all the existing experimental mass; then it is called a pseudo-NG bosom Typical examples limits; such models are called invisible axion models [11,12]. are axions (A~ [i], familons [2], and Majorons [3,4], associated, Two classes of models are discussed commonly in the literature. respectively, with spontaneously broken Peccei-Quinn [5], fam- One introduces new heavy quarks which carry Peccei-Quinn ily, and lepton-number symmetries. This Review provides brief charge while the usual quarks and leptons do not (KSVZ axion descriptions of each of them and their motivations. or "hadronic axion") [11]. The other does not need additional One common characteristic for all these particles is that quarks but requires two Higgs doublets, and all quarks and their couplingto the Standard Modelparticles are suppressed by leptons carry Peccei-Quinn charges (DFSZ axion or "GUT- the energy scale of symmetry breaking, i.e. the decay constant axion") [12]. All models contain at least one electroweak singlet f, where the interaction is described by the Lagrangian scalar boson which acquires an expectation value and breaks L: = -~ (0~r ~, (1) Peccei-Quinn symmetry. The invisible axion with a large decay constant fA ~ 1012 GeV was found to be a good candidate" where J~ is the Noether current of the spontaneously broken of the cold dark matter component of the Universe [13](see global symmetry. Dark Matter review). The enexgy density is stored in the low- An axion gives a natural solution to the strong CP problem: momentum modes of the axion field which are highly occupied why the effective 8-parameter in the QCD Lagrangian L:0 = and thus represent essentially classical field oscillations. eff~'-~~" uu is so small (Serf ~ 10 -9) as required by the The constraints on the invisible axion from astrophysics current limits on the neutron electric dipole moment, even are derived from interactions of the axion with either photons, though 8eft ~ O(1) is perfectly allowed by the QCD gauge electrons or nucleons. The strengths of the interactions are invariance. Here, 8eft is the effective 8 parameter after the model dependent (i.e., not a function of fA only), and hence diagonalization of the quark masses, and F u~a is the gluon one needs to specify a model in order to place lower bounds field strength and F~-a u = 1 ~uupa Fpaa . An axion is a pseudo- on fA. Such constraints will be discussed in Part II. Serious NG boson of a spontaneously broken Peccei-Quinn symmetry, experimental searches for an invisible axion are underway; which is an exact symmetry at the classical level, but is broken they typically rely on axion-photon coupling, and some of quantum mechanically due to the triangle anomaly with the them assume that the axion is the dominant component of gluons. The definition of the Peccei-Quinn symmetry is model our galactic halo density. Part III will discuss experimental dependent. As a result of the triangle anomaly, the axion techniques and limits. acquires an effective coupling to gluons
_ .~, (2) 265 See key on page 213 Gauge & Higgs Boson Particle Listings Axions (A ~ and Other Very Light Bosons
Familons arise when there is a global family symmetry References broken spontaneously. A family symmetry interchanges gener- 1. S. Weinherg, Phys. Rev. Lett. 40, 223 (1978); ations or acts on different generations differently. Such a sym- F. Wilczek, Phys. Rev. Lett. 40, 279 (1978). metry may explain the structure of quark and lepton masses 2. F. Wilezek, Phys. Rev. Lett. 49, 1549 (1982). and their mixings. A familon could be either a scalar or a 3. Y. Chikashige, R.N. Mohapatra, and R.D. Peccei, Phys. pseudoscalar. For instance, an SU(3) family symmetry among Lett. 98B, 265 (1981). three generations is non-anomalous and hence the familons 4. G.B. Gelmini and M. Roncadelli, Phys. Lett. 99B, 411 are exactly massless. In this case, familons are scalars. If (1981). one has larger family symmetries with separate groups of 5. R.D. Peccei and H. Quinn, Phys. Rev. Lett. 38, 1440 (1977); also Phys. Rev. D16, 1791 (1977). left-handed and right-handed fields, one also has pseudoscalar 6. Our normalization here is the same as fa used in G.G. Raf- familons. Some of them have flavor-off-diagonal couplings such felt, Phys. Reports 198, 1 (1990). See this Review for as OuCFdT~s/Fds or O~CbF~')'Ul~/F#e, and the decay constant the relation to other conventions in the literature. F can be different for individual operators. The decay con- 7. T.W. Donnelly et al., Phys. Rev. D18, 1607 (1978); stants have lower bounds constrained by flavor-changing pro- S. Barshay et al., Phys. Rev. Lett. 46, 1361 (1981); cesses. For instance, B(K + --* 7r+r < 3 x 10 -l~ [14] gives A. Barroso and N.C. Mukhopadhyay, Phys. Lett. 106B, 91 (1981); Fds > 3.4 x 1011 GeV [15]. The constraints on familons primarily R.D. Peccei, in Proceedings of Neutrino '8I, Honolulu, coupled to third generation are quite weak [15]. Hawaii, Vol. 1, p. 149 (1981); If there is a global lepton-number symmetry and if it L.M. Krauss and F. Wilczek, Phys. Lett. B173, 189 breaks spontaneously, there is a Majoron. The triplet Majoron (1986). model [4] has a weak-triplet Higgs boson, and Majoron couples 8. J. Schweppe et al., Phys. Rev. Lett. 51, 2261 (1983); to Z. It is now excluded by the Z invisible-decay width. The T. Cowan et al., Phys. Rev. Lett. 54, 1761 (1985). model is viable if there is an additional singlet Higgs boson and 9. R.D. Peccei, T.T. Wu, and T. Yanagida, Phys. Lett. B172, 435 (1986). if the Majoron is mainly a singlet [16]. In the singlet Majoron 10. W.A. Bardeen, R.D. Peccei, and T. Yanagida, Nucl. Phys. model [3], lepton-number symmetry is broken by a weak- B279, 401 (1987). singlet scalar field, and there are right-handed neutrinos which 11. J.E. Kim, Phys. Rev. Lett. 43, 103 (1979); acquire Majorana masses. The left-handed neutrino masses are M.A. Shifman, A.I. Vainstein, and V.I. Zakharov, Nucl. generated by a "seesaw" mechanism [17]. The scale of lepton Phys. B166, 493 (1980). number breaking can be much higher than the electroweak 12. A.R. Zhitnitsky, Soy. J. Nucl. Phys. 31, 260 (1980); scale in this case. Astrophysical constraints require the decay M. Dine and W. Fischler, Phys. Lett. 120B, 137 (1983). constant to be >~ 109 GeV [18]. 13. J. Preskill, M. Wise, F. Wilczek, Phys. Lett. 120B, 127 There is revived interest in a long-lived neutrino, to improve (1983); L. Abbott and P. Sikivie, Phys. Lett. 120B, 133 (1983); Big-Bang Nucleosynthesis [19] or large scale structure formation M. Dine and W. Fischler, Phys. Lett. 120B, 137 (1983); theories [20]. Since a decay of neutrinos into electrons or M.S. Turner, Phys. Rev. D33, 889 (1986). photons is severely constrained, these scenarios require a familon 14. S. Adler et al., hep-ex/9708031. (Majoron) mode Ul -~ v2r (see, e.g., Ref. 15 and references 15. J. Feng, T. Moroi, H. Murayama, and E. Schnapka, UCB- therein). PTH-97/47. Other light bosons (scalar, pseudoscalar, or vector) are 16. K. Choi and A. Santamaria, Phys. Lett. B267, 504 (1991). constrained by "fifth force" experiments. For a compilation of 17. T. Yanagida, in Proceedings o] Workshop on the Unified constraints, see Ref. 21. Theory and the Baryon Number in the Universe, Tsukuba, Japan, 1979, edited by A. Sawada and A. Sugamoto (KEK, It has been widely argued that a fundamental theory will Tsukuba, 1979), p. 95; not possess global symmetries; gravity, for example, is expected M. Gell-Mann, P. Ramond, and R. Slansky, in Supergrav- to violate them. Global symmetries such as baryon number ity, Proceedings of the Workshop, Stony Brook, New York, arise by accident, typically as a consequence of gauge symme- 1979, edited by P. Van Nieuwenhuizen and D.Z. Freedman tries. It has been noted [22] that the Peccei-Quinn symmetry, (North-Holland, Amsterdam, 1979), p. 315. from this perspective, must also arise by accident and must 18. For a recent analysis of the astrophysical bound on axion- electron coupling, see G. Raffelt and A. Weiss, Phys. Rev. hold to an extraordinary degree of accuracy in order to solve D51, 1495 (1995). A bound on Majoron decay constant the strong CP problem. Possible resolutions to this problem, can be inferred from the same analysis.. however, have been discussed [22,23]. String theory also pro- 19. M. Kawasaki, P. Kernan, H.-S. Kang, R.J. Scherrer, vides sufficiently good symmetries, especially using a large G. Steigman, and T.P. Walker, Nucl. Phys. B419, 105 compactification radius motivated by recent developments in (1994); S. Dodelson, G. Gyuk, and M.S. Turner, Phys. Rev. D49, M-theory [24]. 5068 (1994); J.R. Rehm, G. Raffelt, and A. Weiss, astro-ph/9612085; M. Kawasaki, K. Kohri, and K. Sato, astro-ph/9705148. Gauge & Higgs Boson Particle Listings Axions (A ~ and Other Very Light Bosons
20. M. White, G. Gelmini, and J. Silk, Phys. Rev. D51, 2669 for a baryonic or leptonic gauge coupling [6]. (1995); In analogy to neutral pions, axions A ~ couple to photons as S. Bharadwaj and S.K. Kethi, astro-ph/9707143. gATE. B CA which allows for the Primakoff conversion 7 ~-~ A ~ 21. E.G. Adelberger, B.R. Heckel, C.W. Stubbs, and W.F. in external electromagnetic fields. The most restrictive limit Rogers, Ann. Rev. Nucl. and Part. Sci. 41, 269 (1991). arises from globular-cluster stars [2] 22. M. Kamionkowski and J. March-Russell, Phys. Lett. B282, 137 (1992); gA7 <~0.6 X 10 -10 GeV -1 . (3) R. Holman et al., Phys. Lett. B282, 132 (1992). 23. R. Kallosh, A. Linde, D. Linde, and L. Susskind, Phys. The often-quoted "red-giant limit" [7] is slightly weaker. Rev. D52,912 (1995). The duration of the SN 1987A neutrino signal of a few 24. See, for instance, T. Bar&s and M. Dine, Nucl. Phys. seconds proves that the newborn neutron star cooled mostly by B479, 173 (1996); Nucl. Phys. B505, 445 (1997). neutrinos rather than through an "invisible channel" such as right-handed (sterile) neutrinos or axions [8]. Therefore, AXIONS AND OTHER VERY LIGHT BOSONS: PART II (ASTROPHYSICAL CONSTRAINTS) 3 x Io-IO~gAN~3 X 10 -7 (4) (by G.G. Raffelt) is excluded for the pseudoscalar Yukawa coupling to nucleons [2]. Low-mass weakly-interacting particles (neutrinos, gravitons, The "strong" coupling side is allowed because axions then escape axions, baryonic or leptonic gauge bosons, etc.) are produced in only by diffusion, quenching their efficiency as an energy-loss hot plasmas and thus represent an energy-loss channel for stars. channel [9]. Even then the range The strength of the interaction with photons, electrons, and nucleons can be constrained from the requirement that stellar- 10 -6 ~< gAN 5 10-3 (5) evolution time scales are not modified beyond observational is excluded to avoid excess counts in the water Cherenkov limits. For detailed reviews see Refs. [1,2]. detectors which registered the SN 1987A neutrino signal [11]. The energy-loss rates are steeply increasing functions of In terms of the Pcccei-Qninn scale fA, the axion couplings temperature T and density p. Because the new channel has to nucleons and photons are gnN = CNmN/fA (N = n or p) to compete with the standard neutrino losses whict~ tend to and gA.y ---- (a/2rfA)(E/N- 1.92) where CN and E/g are increase even faster, the best limits arise from low-mass stars, model-dependent numerical parameters of order unity. With notably from horizontal-branch (HB) stars which have a helium- mA = 0.62eV(IOTGeV/fA), Eq. (3) yields mA<~0.4eV for burning core of about 0.5 solar masses at (p) ~ 0.6 x 104 g cm -3 E/N = 8/3 as in GUT models or the DFSZ model. The and (T) ~ 0.7 • 108 K. The new energy-loss rate must not ex- SN 1987A limit is mA ~ 0.008eV for KSVZ axions while it ceed about 10 ergs g-1 s-1 to avoid a conflict with the observed varies between about 0.004 and 0.012eV for DFSZ axions, number ratio of HB stars in globular clusters. Likewise the igni- depending on the angle fl which measures the ratio of two tion of helium in the degenerate cores of the preceding red-giant Higgs vacuum expectation values [10]. In view of the large phase is delayed too much unless the same constraint holds at uncertainties it is good enough to remember raA < 0.01 eV as a (p) ~ 2 x 105gcm -3 and (T) ~ 1 x 108K. The white-dwarf generic limit (Fig. 1). luminosity function also yields useful bounds. In the early universe, axions come into thermal equilibrium The new bosons X ~ interact with electrons and nucleons only if fA < 108 GeV [12]. Some fraction of the relic axions with a dimensionless strength g. For scalars it is a Yukawa end up in galaxies and galaxy clusters. Their decay a ~ 27 coupling, for new gauge bosons (e.g., from a baryonic or leptonic contributes to the cosmic extragalactic background light and gauge symmetry) a gauge coupling. Axion-like pseudoscalars to line emissions from galactic dark-matter haloes and galaxy couple derivatively as f-lr r OUdpx with f an energy scale. clusters. An unsuccessful "telescope search" for such features Usually this is equivalent to (2m/f)~,b75r Cx with m the mass yields ma < 3.5 eV [13]. For ma > 30 eV, the axion lifetime is of the fermion r so that g = 2m/f. For the coupling to shorter than the age of the universe. electrons, globular-cluster stars yield the constraint For fA > 108 GeV cosmic axions are produced nonthermally. gxe < { 0.5 • 10 -12 for pseudoscalars [3] , (1) If inflation occurred after the Peccei-Quinn symmetry breaking 1.3 x 10 -14 for scalars [4] , or if Treheat < fA, the "misalignment mechanism" [14] leads to a contribution to the cosmic critical density of if mx ~ 10keV. The Compton process 7 + 4He --~ 4He-}-X~ limits the coupling to nucleons to gXN ~ 0.4 x 10 -10 [4]. ~A h2 ~ 1.9 X 34-1 (1 ~eV/mA) 1"175 O2F(Oi) (6) Scalar and vector bosons mediate long-range forces which are severely constrained by "fifth-force" experiments [5]. In the where h is the Hubble constant in units of 100kms -1 Mpc -1. massless case the best limits come from tests of the equivalence The stated range reflects recognized uncertainties of the cosmic principle in the solar system, leading to conditions at the QCD phase transition and of the temperature- dependent axion mass. The function F(O) with F(0) = 1 and gs,L ~ 10 -23 (2) F(r) = oo accounts for anharmonic corrections to the axion 267 See key on page 213 Gauge & Higgs Boson Particle Listings Axions (A~ and Other Very Light Bosons
matter component. Battye and Shellard [18] found that the dominant source of axion radiation are string loops rather than Inflation String fA scenario scenario long strings. At a cosmic time t the average loop creation size [OeV] neV ~/~ Too much is parametrized as Ill = at while the radiation power is P = ~# 10 is H dark matter with # the renormalized string tension. The loop contribution [~/'/JU.S. Axion Search to the cosmic axion density is [18] peV ~a~ ' (Livermore) 10 c~cz TM 1:~ VI r-1 flAh2 ~ 88 x 3:e' [(I + a/,Q 3/2 - I] (I l~eV/mA) I'175 , (7) Eil a'J LJ (Kyoto Search) I'!:::]Dark where the stated nominaluncertainty has the same source as in r meV U Matter I Eq. (6). The values of a and ,~ are not known, but probably 0.I < ~/,~ < 1.0 [18], taking the expression in square brackets a ~ SN 1967A: eV ~ ~ ~ Too much to 0.15-1.83. If axioms are the dark matter, we have l0 s ! energy loss i- Too many 0.05 5 aA h2 5 0.50, (8) events in keV detectors 10 a ~- where it was assumed that the universe is older than 10 Gyr, t i- 1' Globular cluster stars that the dark-matter density is dominated by axioms with 7r~A Laboratory experiments OA~>0.2, and that h>0.5. This implies mA = 6-2500 peV for the plausible mass range of dark-matter axions (Fig. 1). Contrary to Ref. 18, Sikivie et al. [19] find that the mo- Figure 1: Astrophysical and cosmological exclu- tion of global strings is strongly damped, leading to a flat sion regions (hatched) for the axion mass mA or axion spectrum. In Battye and Shellard's treatment the axion equivalently, the Peccei-Quinn scale fA. An "open end" of an exclusion bar means that it represents radiation is strongly peaked at wavelengths of order the loop a rough estimate; its exact location has not been size. In Sikivie et al.'s picture more of the string radiation goes established or it depends on detailed model as- into kinetic axion energy which is redshifted so that ultimately sumptions. The globular cluster limit depends on there are fewer axions. In this scenario the contributions from the axion-photon coupling; it was assumed that string decay and vacuum realignment are of the same order of E/N = 8/3 as in GUT models or the DFSZ model. The SN 1987A limits depend on the axion-nucleon magnitude; they are both given by Eq. (6) with Oi of order one. couplings; the shown case corresponds to the KSVZ As a consequence, Sikivie et al. allow for a plausible range of model and approximately to the DFSZ model. The dark-matter axions which reaches to smaller masses as indicated dotted "inclusion regions" indicate where axions in Fig. 1. could plausibly be the cosmic dark matter. Most of the allowed range in the inflation scenario requires The work of both groups implies that the low-mass end of fine-tuned initial conditions. In the string scenario the plausible mass interval in the string scenario overlaps with the plausible dark-matter range is controversial as the projected sensitivity range of the U.S. search experiment for indicated by the step in the low-mass end of the galactic dark-matter axioms (Livermore) [20] and of the Kyoto "inclusion bar" (see main text for a discussion). search experiment CARRACK [21] as indicated in Fig. 1. (See Also shown is the projected sensitivity range of the search experiments for galactic dark-matter axioms. also Part III of this Review by Hagmann, van Bibber, and Rosenberg.) In summary, a variety of robust astrophysical arguments and potential. Because the initial misalignment angle Oi can be laboratory experiments (Fig. 1) indicate that mA < 10 -2 eV. very small or very close to 7r, there is no real prediction for The exact value of this limit may change with a more sophis- the mass of dark-matter axions even though one would expect ticated treatment of supernova physics and/or the observation O2F(Oi) ~ 1 to avoid fine-tuning the initial conditions. of the neutrino signal from a future galactic supernova, but A possible fine-tuning of Oi is limited by inflation-induced a dramatic modification is not expected unless someone puts quantum fluctuations which in turn lead to temperature fluctu- forth a completely new argument. The stellar-evolution limits ations of the cosmic microwave background [15,16]. In a broad shown in Fig. 1 depend on the axion couplings to various par- class of inflationary models one thus finds an upper limit to mA ticles and thus can be irrelevant in fine-tuned models where, where axioms could be the dark matter. According to the most recent discussion [16] it is about 10 -3 eV (Fig. 1). for example, the axion-photon coupling strictly vanishes. For nearly any mA in the range generically allowed by stellar evo- If inflation did not occur at all or if it occurred before lution, axions could be the cosmic dark matter, depending on the Peccei-Quinn symmetry breaking with Treheat > fA, cosmic the cosmological scenario realized in nature. It appears that axion strings form by the Kibble mechanism [17]. Their motion our only practical chance to discover these "invisible" particles is damped primarily by axion emission rather than gravitational rests with the ongoing or future search experiments for galactic waves. After axions acquire a mass at the QCD phase transition dark-matter. they quickly become nonrelativistic and thus form a cold dark Gauge & Higgs Boson Particle Listings Axions (A ~ and Other Very Light Bosons
References AXIONS AND OTHER VERY LIGHT BOSONS, 1. M.S. Turner, Phys. Reports 197, 67 (1990); PART III (EXPERIMENTAL LIMITS) G.G. Raffelt, Phys. Reports 198, 1 (1990). (by C. Hagmann, K. van Bibber, and L.J. Rosenberg) 2. G.G. Raffelt, Stars as Laboratories for Fundamental Physics (Univ. of Chicago Press, Chicago, 1996). In this section we review the experimental methodology 3. D.A. Dicus, E.W. Kolb, V.L. Teplitz, and R.V. Wagoner, and limits on light axions and light pseudoscalars in gen- Phys. Rev. D18, 1829 (1978); eral. (A comprehensive overview of axion theory is given by G.G. Raffelt and A. Weiss, Phys. Rev. D51, 1495 (1995). H. Murayama in the Part I of this Review, whose notation we 4. J.A. Grifols and E. MassS, Phys. Lett. B173, 237 (1986); follow [1].) Within its scope are searches where the axion is as- J.A. Grifols, E. MassS, and S. Peris, Mod. Phys. Lett. A4, sumed to be dark matter, searches where the Sun is presumed to 311 (1989). be a source of axions, and purely laboratory experiments. We 5. E. Fischbach and C. Talmadge, Nature 356, 207 (1992). restrict the discussion to axions of mass mA < O(eV), as the al- 6. L.B. Okun, Yad. Fiz. 10, 358 (1969) [Sov. J. Nucl. Phys. lowed range for the axion mass is nominally 10-6 < mA < 10 -2 10, 206 (1969)]; S.I. Blinnikov et al., Nucl. Phys. B458, 52 (1996). eV. Experimental work in this range predominantly has been 7. G.G. Raffelt, Phys. Rev. D33, 897 (1986); through the axion-photon coupling gAT, to which the present G.G. Raffelt and D. Dearborn, ibid. 36, 2211 (1987). review is confined. As discussed in Part II of this Review by 8. J. Ellis and K.A. Olive, Phys. Lett. B193, 525 (1987); G. Raffelt, the lower bound derives from a cosmological overclo- G.G. Raffelt and D. Seckel, Phys. Rev. Lett. 60, 1793 sure argument, and the upper bound from SN1987A [2]. Limits (1988). from stellar evolution overlap seamlessly above that, connecting 9. M.S. Turner, Phys. Rev. Lett. 60, 1797 (1988); with accelerator-based limits which ruled out the original axion. A. Burrows, T. Ressel, and M. Turner, Phys. Rev. D42, 3297 (1990). There it was assumed that the Peccei-Quinn symmetry-breaking 10. H.-T. Janka, W. Keil, G. Raffelt, and D. Seckel, Phys. scale was the eleetroweak scale, i.e., fA "~ 250 GeV, implying Rev. Lett. 76, 2621 (1996); axions of mass mA "~ O(100keV). These earlier limits from W. Keil et al., Phys. Rev. D56, 2419 (1997). nuclear transitions, particle decays, etc., while not discussed 11. J. Engel, D. Seckel, and A.C. Hayes, Phys. Rev. Lett. 65, here, are included in the Listings. 960 (1990). While the axion mass is well determined by the Peccei- 12. M.S. Turner, Phys. Rev. Lett. 59, 2489 (1987). Quinn scale, i.e., mA = 0.62 eV (107GeV/fA), the axion- 13. M.A. Bershady, M.T. Ressell, and M.S. Turner, Phys. Rev. photon coupling gA7 is not: gA7 = (a/nfA)gT, with g7 = Lett. 66, 1398 (1991); (E/N - 1.92)/2, where E/N is a model-dependent number. It M:T. Ressell, Phys. Rev. D44, 3001 (1991); J.M. Overduin and P.S. Wesson, Astrophys. J. 414, 449 is noteworthy however, that two quite distinct models lead to (1993). axion-photon couplings which are not very different. For the 14. J. Preskill, M. Wise, and F. Wilczek, Phys. Lett. B120, case of axions imbedded in Grand Unified Theories, the DFSZ 127 (1983); axion [3], g7 = 0.37, whereas in one popular implementation of L. Abbott and P. Sikivie, ibid. 133; the "hadronic" class of axions, the KSVZ axion [4], g7 = -0.96. M. Dine and W. Fischler, ibid. 137; M.S. Turner, Phys. Rev. D33, 889 (1986). The Lagrangian L = gA7 E. B CA, with CA the axion field, permits the conversion of an axion into a single real photon in 15. D.H. Lyth, Phys. Lett. B236, 408 (1990); M.S. Turner and F. Wilczek, Phys. Rev. Lett. 66, 5 (1991); an external electromagnetic field, i.e., a Primakoff interaction." A. Linde, Phys. Lett. B259, 38 (1991). In the case of relativistic axions, k 7 -kA ~ m2A/2w << w, 16. E.P.S. Shellard and R.A. Battye, "Inflationary axion cos- pertinent to several experiments below, coherent axion-photon mology revisited", in preparation (1998); mixing in long magnetic fields results in significant conversion The main results can be found in: E.P.S. Shellard and probability even for very weakly coupled axions [5]. R.A. Battye, astro-ph/9802216. Below are discussed several experimental techniques con- 17. R.L. Davis, Phys. Lett. B180, 225 (1986); R.L. Davis and E.P.S. Shellard, Nucl. Phys. B324, 167 straining gAT, and their results. Also included are recent but (1989). yet-unpublished results, and projected sensitivities for experi- 18. R.A. Battye and E.P.S. Shellard, Nucl. Phys. B423, 260 ments soon to be upgraded. (1994); III.I. Microwave cavity experiments: Possibly the most Phys. Rev. Lett.. 73, 2954 (1994) (E) ibid. 76, 2203 (1996); astro-ph/9706014, to be published in: Proceedings Dark promising avenue to the discovery of the axion presumes that Matter 96, Heidelberg, ed. by H.V. Klapdor-Kleingrothaus axions constitute a significant fraction of the dark matter and Y. Ramacher. halo of our galaxy. The maximum likelihood density for the 19. D. Harari and P. Sikivie, Phys. Lett. B195, 361 (1987); Cold Dark Matter (CDM) component of our galactic halo is C. Hagmann and P. Sikivie, Nucl. Phys. B363, 247 (1991). PCDM ---- 7.5 X 10-25g/cma(450MeV/cm3) [6]. That the CDM 20. C. Hagmann et al., Phys. Rev. Left. 80, 2043 (1998). halo is in fact made of axions (rather than e.g. WIMPs) is in 21. I. Ogawa, S. Matsuki, and K. Yamamoto, Phys. Rev. D53, principle an independent assumption, however should very light R1740 (1996). axions exist they would almost necessarily be cosmologically 269 See key on page 213 Gauge & Higgs Boson Particle Listings Axions (A~ and Other Very Light Bosons abundant [2]. As shown by Sikivie [7], halo axions may be de- tected by their resonant conversion into a quasi-monochromatic 10-14 microwave signal in a high-Q cavity permeated by a strong mag- netic field. The cavity is tunable and the signal is maximum 10-15 when the frequency u = mA(1 + O(10-6)), the width of the 10-16 peak representing the virial distribution of thermalized axions in the galactic gravitational potential. The signal may possess ( OAy ~ 10"17 ultra-fine structure due to axions recently fallen into the galaxy V"~-A . GsV'21 10-18 and not yet thermalized [8]. The feasibility of the technique ev-Z~J was established in early experiments of small sensitive volume, 10-I9 V = O(lliter) [9,10] with High Electron Mobility Transistor i!...... s?~,~sl,oto,ol t! ~ OFSZ 10-20 ...... IZ~" (HEMT) amplifiers, which set limits on axions in the mass range 4.5 < mA < 16.3 #eV, but at power sensitivity levels 2-3 10-21 orders of magnitude too high to see KSVZ and DFSZ axions 10-6 m^ [eV] 10"5 (the conversion power PA~v cx g~7)" A recent large-scale ex- periment (B -~ 7.5 T, V ,,, 200 liter) has achieved sensitivity to Figure 2: Exclusion region from the microwave cav- KSVZ axions over a narrow mass range 2.77 < mA < 3.3 #eV, ity experiments, where the plot is flattened by present- and continues to take data [11]. The exclusion regions shown ing (gA3,/mA) 2 vs. m A. The first-generation experi- in Fig. 1 for Refs. [9-12] are all normalized to the best-fit Cold ments (Rochester-BNL-FNAL, "RBF" [9]; University Dark Matter density PCDM = 7.5 • 10-25g/cm3(450 MeV/cm3), of Florida, "UF" [10]) and the US large-scale exper- iment in progress ("US" [11]) are all HEMT-based. and 90% CL. Recent developments in DC SQUID amplifiers [12] Shown also is the full mass range to be covered and Rydberg atom single-quantum detectors [13[ promise dra- by the latter experiment (shaded line), and the im- matic improvements in noise temperature, which will enable proved sensitivity when upgraded with DC SQUID rapid scanning of the axion mass range at or below the DFSZ amplifiers [12] (shaded dashed line). The expected performance of the Kyoto experiment based on a Ry- limit. The region of the microwave cavity experiments is shown dberg atom single-quantum receiver (dotted line) is in detail in Fig. 2. also shown [13].
111.2. Telescope search for eV axions: For axions of 10-4 mass greater than about 10 -1 eV, their cosmological abundance is no longer dominated by vacuum misalignment or string ra- 10.6 diation mechanisms, but rather by thermal production. Their contribution to the critical density is small, f2 ,,~ 0.01 (rnA/eV).
104 However, the spontaneous-decay lifetime of axions, 7-(A --* "7 27) "~ 1025sec(mA/eV) -5 while irrelevant for peV axions, is short enough to afford a powerful constraint on such thermally ~ 10qo produced axions in the eV range, by looking for a quasi- monochromatic photon line from galactic clusters. This line, 10 -12 corrected for Doppler shift, would be at half the axion mass and its width would be consistent with the observed virial motion, 10 -14 typically A,~/)~ ~, 10 -2. The expected line intensity would be of the order I A ~ lO-17(mA/3eV)Tergcm-2arcsec-2~-lsec -1
10-16 for DFSZ axions, comparable to the continuum night emission. 10-6 10-5 10-4 10-3 10-2 10-1 10~ 101 102 The conservative assumption is made that the relative density m A (eV) of thermal axions fallen into the cluster gravitational poten- tial reflects their overall cosmological abundance. A search for thermal axions in three rich Abell clusters was carried out at Figure 1: Exclusion region in mass vs. axion- Kitt Peak National Laboratory [14]; no such line was observed photon coupling (mA, gAT) for various experiments. The limit set by globular cluster Horizontal Branch between 3100-8300 ~ (mA = 3-8 eV) after "on-off field" sub- Stars ("HB StarS") is shown for Ref. 2. traction of the atmospheric molecular background spectra. A limit everywhere stronger than gA7 < 10-1~ is set, which is seen from Fig. 1 to easily exclude DFSZ axions throughout the mass range. 270 Gauge & Higgs Boson Particle Listings Axions (A ~ and Other Very Light Bosons
111.3. A search for solar azions: As with the telescope comparable to those from stellar evolution would be achievable. search for thermally produced axions above, the search for Due to the g~7 rate suppression however, it does not seem solar axions was stimulated by the possibility of there being a feasible to reach standard axion couplings. "1 eV window" for hadronic axions (i.e., axions with no tree- III.5. Polarization ezperiments: The existence of axions level coupling to leptons), a "window" subsequently closed by an can affect the polarization of light propagating through a improved understanding of the evolution of globular cluster stars transverse magnetic field in two ways [22]. First, as the Ell and SN1987A [2]. Hadronic axions would be copiously produced component, but not the E• component will be depleted by within our Sun's interior by a Primakoff process. Their flux at the production of real axions, there will be in general a small the Earth of ~ 1012cm-2sec-l(mA/eV) 2, which is independent rotation of the polarization vector of linearly polarized light. of the details of the solar model, is sufficient for a definitive This effect will be a constant for all sufficiently light mA such test via the axion reconversion to photons in a large magnetic that the oscillation length is much longer than the magnet field. However, their average energy is ,-~ 4 keV, implying an (m2Al/2w << 27r). For heavier axions, the effect oscillates and oscillation length in the vacuum of 27r(m~/2w) -1 ~ O(mm), diminishes with increasing mA, and vanishes for mA ~> w. The precluding the mixing from achieving its theoretically maximum second effect is birefringence of the vacuum, again because there wlue in any practical magnet. It was recognized that one could can be a mixing of virtual axions in the E H state, but not for endow the photon with an effective mass in a gas, m~ = Wp|, the E• state. This will lead to light which is initially linearly thus permitting the axion and photon dispersion relationships polarized becoming elliptically polarized. Higher-order QED to be matched [15]. A first simple implementation of this also induces vacuum birefringence, and is much stronger than proposal was carried out using a conventional dipole magnet the contribution due to axions. A search for both polarization- with a conversion volume of variable-pressure helium gas and rotation and induced ellipticity has been carried out with the a xenon proportional chamber as the x-ray detector [16]. The same magnets described in Sec. (III.4) above [21,23]. As in magnet was fixed in orientation to take data for ~ 1000 sec/day. the case of photon regeneration, the observables are boosted Axions were excluded for gA~ < 3.6 x 10-9GeV -1 for m A < linearly by the number of passes the laser beam makes in 0.03eV, and g.A'y < 7.7 • 10-9GeV -1 for 0.03eV< mA <0.11 an optical cavity within the magnet. The polarization-rotation eV (95% CL). A more ambitious experiment has recently been resulted in a stronger limit than that from ellipticity, gA~ < commissioned, using a superconducting magnet on a telescope 3.6 x 10-7GeV -1 (95% CL) for m A < 5 x 10 -4 eV. The mount to track the Sun continuously. A preliminary exclusion limits from ellipticity are better at higher masses, as they limit of gA~ < 6 x 10-1~ -1 (95% CL) has been set for fall off smoothly and do not terminate at mA. There are two mA < 0.03 eV [17]. experiments in construction with greatly improved sensitivity Another search for solar axions has been carried out, using which while still far from being able to detect standard axions, a single crystal germanium detector. It exploits the coherent should measure the QED "light-by-light" contribution for the conversion of axions into photons when their angle of incidence first time [24,25]. The overall envelope for limits from the satisfies a Bragg condition with a crystalline plane. Analysis laser-based experiments in Sec. (III.4) and Sec. (III.5) is shown of 1.94 kg-yr of data from a 1 kg germanium detector yields schematically in Fig. 1. a bound of gA~ < 2.7 x 10-9GeV -1 (95% CL), independent of mass up to ma ~ 1 keV [18]. References III.4. Photon regeneration ("invisible light shining 1. H. Murayama, Part I (Theory) of this Review. through walls"): Photons propagating through a transverse 2. G. Raffelt, Part II (Astrophysical Constraints) of this field (with EIIB ) may convert into axions. For light axions Review. with m2Al/2w << 2~r, where l is the length of the magnetic 3. M. Dine et. al., Phys. Lett. B104, 199 (1981); A. Zhitnitsky, Soy. J. Nucl. Phys. 31,260 (1980). field, the axion beam produced is colinear and coherent with 4. J. Kim, Phys. Rev. Lett. 43, 103 (1979); the photon beam, and the conversion probability H is given M. Shifman et al., Nucl. Phys. B166, 493 (1980). by H ~ (1/4)(gA~Bl) 2. An ideal implementation for this limit 5. G. Raffelt and L. Stodolsky, Phys. Rev. D37, 1237 (1988). is a laser beam propagating down a long, superconducting 6. E. Gates et al., Ap. J. 449, 123 (1995). dipole magnet like those for high-energy physics accelerators. 7. P. Sikivie, Phys. Rev. Lett. 51, 1415 (1983); If another such dipole magnet is set up in line with the 52(E), 695 (1984); first, with an optical barrier interposed between them, then Phys. Rev. D32, 2988 (1985). photons may be regenerated from the pure axion beam in 8. P. Sikivie and J. Ipser, Phys. Lett. B291, 288 (1992); the second magnet and detected [19]. The overall probability P. Sikivie et al., Phys. Rev. Lett. 75, 2911 (1995). P('y --+ A --+ 7) = YI2. Such an experiment has been carried 9. S. DePanfilis et al., Phys. Rev. Lett. 59, 839 (1987); out, utilizing two magnets of length l= 4.4 m and B-- 3.7 T. W. Wuensch et al., Phys. Rev. D40, 3153 (1989). Axions with mass m A < 10 -3 eV, and gAff > 6.7 x 10-TGeV -1 10. C. Hagmann et al., Phys. Rev. D42, 1297 (1990). were excluded at 95% CL [20,21]. With sufficient effort, limits 11. C. Hagmann et al., Phys. Rev. Lett. 80, 2043 (1998). 12. M. Miick et al., to be published in Appl. Phys. Lett. 271 See key on page 213 Gauge & Higgs Boson Particle Listings Axions (A ~ and Other Very Light Bosons
13. I. Ogawa et al., Proceedings II. RESCEU Conference on <1.1 x 10 -8 90 IOALLIEGRO 92 SPEC K + ~ ~r+AO (A0 --~ e§ "Dark Matter in the Universe and its Direct Detection," <5 x 10 -4 90 11 ATIYA 92 B787 1c0 ~ "fX 0 p. 175, Universal Academy Press, ed. M. Minowa (1997). <4 • 10 -6 90 12 MEIJERDREES92 SPEC lr 0 -* "fX 0' X 0 ~ e+e -, 14. M. Bershady et aL, Phys. Rev. Lett. 66, 1398 (1991); mxo= 100 MeV M. Ressell, Phys. Rev. D44, 3001 (1991). <1 x 10-7 90 13 ATIYA 90B B787 Sup. by KITCH- ING 97 15. K. van Bibber et al., Phys. Rev. D39, 2089 (1989). <1.3 x 10-8 90 14KORENCHE... 87 SPEC 7r+ ~-~ e't-vA 0 (A -~ e+e -) 16. D. Lazarus et aL, Phys. Rev. Lett. 69, 2333 (1992). <1 x 10 -9 90 15 EICHLER 86 SPEC Stopped lr+ --~ 17. M. Minowa, Proceedings International Workshop Non- e+ v A 0 <2 x 10 -5 90 16yAMAZAKI 84 SPEC For 160
<4 x 10.4 90 O 25 ALBRECHT 86D ARG T(15) ~ A03" 38ORITO 89 limit translates to ~A0ee/41r < 6.2 x 10-10. Somewhat more sensitive (A0 ~ /~+#-, limits are obtained for larger mAo: B < 7.6 x 10-6 at 100 keV. ~r+lr -, K+ K -) 39AMALDI 85 set limits B(A03") / B(3"3"3") < (1-51 x 10-6 for mAO = 900-100 keV <8 x 10-4 90 1 26 ALBRECHT 86D ARG T(15) ~ A03' <1.3 x 10-3 90 0 27 ALBRECHT 86D ARG T(1S) ~ A03" which are about 1/10 of the CARBONI 83 limits. 40CARBONI 83 looked for orthoposltronlum --* A03". Set limit for A 0 electron coupling (A0 ~ e + e-, 3'3") <2. x 10 -3 90 28 BOWCOCK 86 CLEO T(2S) ~ T(1S) squared, g~eeAO)2/(4~r) < 6. x 10-10-7. x 10 -9 for mAo from 150-900 keV (CL = A 0 99.7% I. This is about 1/10 of the bound from 8"-2 experiments. <5. x 10-3 90 29 MAGERAS 86 CUSB T(15) ~ A03" <3. xlO -4 90 30ALAM 83 CLEO T(1S)~ A03" <9.1 x 10-4 90 31 NICZYPORUK 83 LENA T(15) ~ A03" A~ (Ax~on) Search In Photowoductlon <1.4 x 10-5 90 32 EDWARDS 82 CBAL J/q~ ~ A03" VALUE DOCUMENT ID COMMENT <3.5 x 10 .4 90 33 SIVERTZ 82 CUSB T(15) ~ A03" * We do not use the following data for averages, fits, limits, etc. <1.2 x 10-4 90 33 SIVERTZ 82 CUSB T(35) ~ A03" 41 BASSOMPIE... 95 mAo = 1.8 • 0.2 MeV 20 BALEST 95 rooked for a monochromatic 3" from T(1S) decay. The bound is for mAo < 41 BASSOMPIERRE 95 is an extension of BASSOMPIERRE 93. They looked for a peak 5.0 GeV. See Fig. 7 In the paper for bounds for heavier mAo. They also quote a bound in the invarlant mass of e+e - pairs In the region me+ e- = 1,8 4- 0.2 MeV. They on branching ratios 10-3~10 -5 of three-body decay 3"XX for O 47MEIJERDREES 92 give r(lr-p ~ nAO).B(A 0 ~ e+e-)/r(=-p ~ all) < 10 -5 A ~ (Axlon) Searches In Reactor Experiment= (90% CL) for mAo = 100 MeV, ~'A0 = 10-11-10 -23 sec. Limits ranging from 2,5 x VALUE DOCUMENTID .TECN COMMENT 10 -3 to 10 -7 are given for mAn = 25-136 MeV. We do not use the following data for averages, fits, limits, etc. 48 BLUEMLEIN 91 Is a proton beam dump experiment at Serpukhov. No candidate event 74ALTMANN 95 CNTR Reactor; A 0 ~ e+e - for A 0 ~ e+e -, 23" are found. Fig. 6 gives the excluded region in mAO-X plane (x= 75 KETOV 86 SPEC Reactor, A 0 ~ "77 tan# = v2/vl). Standard axlon Is excluded for 0.2 < mAn < 3.2 MeV for most 76 KOCH 86 SPEC Reactor; A 0 ~ 3"3" x > 1, 0.2-11 MeV for most x < 1. 77 DATAR 82 CNTR Light water reactor 49 FAISSNER 89 searched for A 0 ~ e + e- in a proton beam dump experiment at SIN. No 78VUILLEUMIER 81 CNTR Reactor, A 0 ~ 2"7 excess of events was observed over the background. A standard axlon with mass 2me-20 74ALTMANN 95 looked for A 0 decaying into e+e - from the Bugey5 nuclear reac- MeV Is excluded, Lower limit on fan of -- 104 GeV is given for mAO = 2me-20 MeV. tor. They obtain an upper limit on the A 0 production rate of ~(AO)/o~('7) xB(A 0 50DEBOER 88 reanalyze EL-NADI 88 data and claim evidence for three distinct states e+e-)< 10 -16 for mAn = 1.5 MeV at 90% CL. The limit is weaker for heavier A 0. In with mass ~ 1.1, ~ 2.1, and ~ 9 MeV, lifetimes 10-16-10-15s decaying to e+e - the case of a standard axlon, this limit excludes a mass In the range 2m e 86AVIGNONE 88 looked for the 1115 keV transition C* ~ CuA 0, either from A 0 107The limits are obtained from their figure 3. Also given is the limit on the 2";' In-flight decay or from the secondary A 0 interactions by Compton and by Primakoff AO~y~-A0 e-}- e- coupling plane by assuming Prlmakoff production. processes. Limits for axion parameters are obtained for mAo < 1.1 MeV. 87 DATAR 88 rule out light pseudescalar particle emission through Its decay A 0 ~ e+ e- In the mass range 1.02-2.5 MeV and lifetime range 10-13-10 -8 s. The above limit is Search for A ~ (Axlon) Resonance in Bhabha Scattering for r = 5 x 10 -13 s and m = 1.7 MeV; see the paper for the r-m dependence of the The limit is for F(A0)[B(A 0 ~ e+e-)] 2. limit. 88The limit Is for the branching fraction of 160*(6.05 MeV, 0 +) ~ 16OX0, X 0 VALUE ( IO-3 eV) CL~ DOCUMENTID TECN COMMENT e +e- against internal pair conversion for mXo = 1.7 McV and rXO < 10-11s. We do not use the fonowlng data for averages, fits, limits, etc. Similar limits are obtained for mXo = 1.3-3.2 MeV. The spin parity of X 0 must be < 1.3 97 108 HALLIN 92 CNTR mA0 = 1.75-1.88 MeV either 0 + or 1-. The limit at 1.7 MeV is translated Into a limit for the X0-nucleon none 0.0016-0.47 90 109 HENDERSON 92C CNTR mAo= 1.5-1.86 MeV coupling constant: 4ojvN/4~ < 2.3 x 10 -9. < 2.0 90 110WU 92 CNTR mAo= 1.56-1.86 MeV 89The DOEHNER 88 limit is for mAo = 1.7 MeV, r(A O) < 10-10 s. Limits less than < 0.013 95 TSERTOS 91 CNTR mAo = 1.832 MeV none 0.19-3.3 95 111WIDMANN 91 CNTR mAo= 1.78-1.92 MeV 10 -4 are obtained for mAo = 1.2-2.2 MeV. < 5 97 BAUER 90 CNTR man = 1.832 MeV 90SAVAGE 88 looked for A 0 that decays into e+e - in the decay of the 9.17 MeV JP = none 0.09-1.5 95 112 JUDGE 90 CNTR mAo = 1.832 MeV, 2 + state in 14N, 17.64 MeV state JP = 1+ in 8Be, and the 18.15 MeV state JP = elastic 1+ In 8Be. This experiment constrains the isovector coupling of A 0 to hadrons, If man < 1.9 97 113TSERTOS 89 CNTR mAo = 1.82 MeV = (1.1 ~ 2.2) MeV and the Isoscalar coupling of A 0 to hadrons, if mAo = (1.1 <(10-40) 97 113TSERTOS 89 CNTR mAo = 1.51-1.65 MeV 2.6) MeV. Both limits are valid only If r(A O) ~,~ 1 x 10 -11 s. <(1-2.5) 97 113 TSERTOS 89 CNTR mAo = 1.80-1.86 MeV 91Limits are for F(A0(1.8 MeV))/F(TrM1); Le., for 1.8 MeV axion emission normalized < 31 95 LORENZ 88 CNTR mAo = 1.646 MeV to the rate for Internal emission of e+e - pairs. Valid for l"A0 < 2 x 10-11s. 6Li < 94 95 LORENZ 88 CNTR mAo = 1.726 MeV Isovector decay data strongly disfavor PECCEI 86 model h whereas the 10B and 14N < 23 95 LORENZ 88 CNTR mAo = 1.782 MeV Isoscalar decay data strongly reject PECCEI 86 model II and IlL < 19 95 LORENZ 88 CNTR mAo = 1.837 MeV 92 SAVAGE 86B looked for A 0 that decays into e + e- in the decay of the 9.17 MeV JP = < 3.8 97 114TSERTOS 88 CNTR mAo = 1.832 MeV 2 + state in 14N. Limit on the branching fraction Is valid if rAO ~ 1. x 10-11s for mAo 115VANKLINKEN 88 CNTR = (1.1-1.7) MeV. This experiment constrains the Iso-vector coupling of A 0 to hadrons. 116 MAIER 87 CNTR 93ANANEV 85 with IBR-2 pulsed reactor exclude standard A 0 at CL = 95% masses below <2500 90 MILLS 87 CNTR mAo = 1.8 MeV 470 keV (LI* decay) and below 2m e for deuteron* decay. 117 VONWIMMER.B7 CNTR 94CAVAIGNAC 83 at Bugey reactor exclude axlon at any mg?Nb,decay and axion with 108HALLIN 92 quote limits on lifetime, 8 x 10-14-5 x 10-13 sec depending on mass, mAo between 275 and 288 keV (deuteron* decay). assuming B(A 0 -* e§ -) = 100%. They say that TSERTOS 91 overstated their 95ALEKSEEV 82 with IBR-2 pulsed reactor exclude standard A0 at CL = 95% mass*ranges sensitivity by a factor of 3. mA0 <400 keV (Li* decay) and 330 keV Search for X ~ (Light Boron) Remnance In e+e - --* *r~/ interaction Lin t = x. For several families of neutrinos, the limit applies for The limit is for F(X 0 ~ e+e-)-F(X 0 ~ "y~,'y)/Ftota I. C invadance forbids spin-0 (zh~)l/4 X 0 coupling to both e + e- and -y-),-~,. 136pICCIOTTO 88 limit applies when mXo < 55 MeV and ~-X0 > 2ns, and It decreases VALUE(10 -3 eV) CL_%% DOCUMENTID TECN COMMENT to 4 x 20-7 at mXo = 125 MeV, beyond which no limit Is obtained. We do not use the following data for averages, fits, limits, etc. 137 GOLDMAN 87 limit corresponds to F > 2.9 x 109 GeV for the family symmetry breaking < 0.2 95 121VO 94 CNTR mx0=1.1-1.9 MeV scale from the Lagranglan Lin t = (Z/F)~/z'y/z (a+b75) ~beOl~#4xO with a2+b 2 = 1. < 1.0 95 122 VO 94 CNTR mxo=l.1 MeV This is not as sensitive as the limit F > 9.9 x 109 GeV derived from the search for ,u+ < 2.5 95 122 VO 94 CNTR mx0=l.4 MeV e + X 0 by JODIDIO 86, but does not depend on the chlrallty property of the coupling. <120 95 122 VO 94 CNTR mxo=l.7 MeV 138Umits are for r(/z ~ eX~ -.-, ev'o). Valid when mxo = 0-93.4, 98.1-103.5 < 3.8 95 1235KALSEY 92 CNTR mxo= 1.5 MeV MeV. 139EICHLER 86 looked for /~+ ~ e+X 0 followed by X 0 ~ e+e -. Limits on the 121VO 94 looked for X 0 ~ -y'y'~ decaying at rest. The precise limits depend on mXO. See branching fraction depend on the mass and and lifetime of X O, The quoted limits are Fig. 2(b) in paper. valid when ~'xO ~ 3. x 10-10 s If the decays are kinematlcally allowed. 122V0 94 looked for X O ~ ~f'~' decaying In flight. 140JODIDIO 86 corresponds to F > 9.9 x 109 GeV for the family symmetry breaking scale 123SKALSEY 92 also give limits 4.3 for mXO = 1.54 and 7.5 for 1.64 MeV. The spin ofX 0 with the padty-conservlng effective Lagrangian Lin t = (l/F) ~#.,/P'~,eO#~AXO. is assumed to be one. 141BALTRUSAITIS 85 search for nght Goldstone boron(X 0) of broken U(1). CL = 95% limits are B 0. ~ /~+ X0)/B(T ~ #+ vv) <0.125 and B(7 ~ e+ X0)/B(~- ~ e + vv) Light Boson (X ~ Search In Nonresonant e+e - Annihilation at Rest <0.04. Inferred limit for the symmetry breaking scale is m >3000 TeV. 142The primordial heavy neutrino must decay into v and famllon, fA, early so that the Limits are for the ratio of n~/ + X 0 production relative to ~/'y. red-shifted decay products are below critical density, see their table. In addition, K VALUE(units 10-6 ) CL% DOCUMENTID TECN COMMENT fffA and/~ --* efA are unseen. Combining these excludes mheavy u between 5 x 10-5 We do not use the following data for averages, fits, limits, etc. and 5 x 10 -4 MeV (# decay) and mheavyv between 5 x 10 -5 and 0,1 MeV (K-decay). < 4.2 90 124 MITSUI 96 CNTR ~X 0 I < 4 68 125 SKALSEY 95 CNTR "yX0 <40 68 126SKALSEY 95 RVUE "yX0 MaJomn Searches In Neutdnok~ Double/~ Decay < 0.18 90 127 ADACHI 94 CNTR ~/'yX 0' X 0 ~ -y-~ Limits are for the half-life of neutdnoless/3~3 decay with a MaJoron emission. < 0.26 90 128ADACHI 94 CNTR "7~,X 0. X 0 ~ ~f~f Previous Indications for neutrinoless double beta decay with maJoron emission have < 0,33 90 129ADACHI 94 CNTR ~/X0' X 0 ~ ~,-~ been superseded. No experiment currently claims any such evidence. For a review, see DOI 88. 124MITSUI 96 looked for a monochromatic ~f. The bound applies for a vector X 0 with | VALUE(~ears) CL_...~ DOCUMENTID TECN COMMENT C=--1 and mxo <200 keV. They derive an upper bound on eeX 0 coupling and ~ence | > 7.2 X 1024 90 143 BERNATOW... cJ2 CNTR 128Te on the branching ratio B(o-Ps ~ "7~fxO)< 6.2 x 10-6. The bounds weaken for heavier We do not use the following data for averages, fits, limits, etc. X 0 . I > 7.91 x 1021 90 144 GUENTHER 96 SPEC 76Ge 125SKALSEY 95 looked for a monochromatic q, without an accompanying-y in e+e - > 1.7 x 1022 90 BECK 93 CNTR 76Ge annihilation. The bound applies for scalar and vector X 0 with C = -1 and mXo = > 7.9 x 1020 68 145 TANAKA 93 SPEC 100Mo 106-1000 keV. 1265KALSEY 95 reinterpreted the bound on ~,A0 decay of o-Ps by ASAI 91 where 3% of > 1.9 x 1020 68 BARABASH 89 CNTR 136Xe delayed annihilations are not from 351 states. The bound applies for scalar and vector > 1.0 x 1021 90 FISHER 89 CNTR 76Ge X 0 with C= -1 and mxo = 0-800 keV. > 3.3 x 1020 90 ALSTON-... 88 CNTR 100Mo (6 • x 1020 AVIGNONE 87 CNTR 76Ge 127ADACHI 94 looked for a peak In the "y-y Invariant mass distribution In q,-f~ production > 1.4 x 1021 90 CALDWELL 87 CNTR 76Ge from e+e - annihilation. The bound applies for mxo = 70-800 keV. > 4.4 x 1020 90 ELLIOTT 87 SPEC 825e 128 ADACHI 94 looked for a peak In the missing-mass mass distribution In "y'y channel, using > 1.2 x 1021 90 FISHER 87 CNTR 76Ge q'q"y*/production from e+e - annihilation. The bound applies for mXo <800 keV, 146 VERGADOS 82 CNTR 129ADACHI 94 looked for a peak in the missing mass distribution In ~,~/ channel, using 143 BERNATOWICZ 92 studied double-/3 decays of 128Te and 130Te, and found the ratio *f'),'),'y production from e+e - annihilation. The bound applies for mXo = 200-900 ~-(130Te)/T(128Te) = (3.52 • 0.11) x 10 -4 In agreement with relatively stable theo- keV. retical predictions. The bound Is based on the requirement that MaJoron-emlttlng decay cannot be larger than the observed double-beta rate of 128Te of (7.7 4- 0.4) x 1024 year. We calculated 90% CL ltmR as (7.7-1.28 x 0.4=7.2) x 1024. Searches for Gadstone Borons (X ~ 1445ee Table I In GUENTHER 96 for limits on the Majoron coupling in different models. (Including Horizontal Borons and MaJorons.) Limits are for branching ratios. 145TANAKA 93 also quote limit 5.3 x 1019 years on two MaJoron emission. VALUE CL~ EVTS DOCUMENTID TECN COMMENT 146VERGADO5 82 sets limit gH < 4 x 10 -3 for (dimensionless) lepton-number violating We do not use the following data for averages, fits, limits, etc. coupling, g'H' of scalar boron (MaJoron) to neutdnos, from analysis of data on double #9 130 BOBRAKOV 91 Electron quasi-magnetic decay of 48Ca. Interaction <3.3 x 10 -2 95 131 ALBRECHT 90E ARG T ~ /zXu. Famllon <1.8 x 10-2 95 131ALBRECHT 90E ARG "r ~ eX O. Famllon Invbible A~ (AxIon) MASS LIMITS from Astroph~ and C~mololg <6.4 x 10-9 90 132 ATIYA 90 B787 K + ~ lr + X 0. v I = v2 is usually assumed (vI = vacuum expectation values). For a review of these Famllon <1.1 x 10-9 90 133 BOLTON 88 CBOX /~+ --~ +•IX O. limits, see RAFFELT 90C and TURNER 90. In the comment nnes below, D and K Fatal• refer to DFSZ and KSVZ axion types, discussed In the above minireview. 134CHANDA 88 ASTR Sun, MaJoron VALUE(eV} DOCUMENT ID TECN COMMENT 135 CHOI 88 ASTR MaJoron, SN 1987A We do not use the following data for averages, fits, limits, etc. <5 x 10-6 go 136 PICCIOTTO 88 CNTR lr ~ evX O, MaJoion < 0.007 147 BORISOV 97 ASTR D, neutron star <1.3 x 10-9 90 137 GOLDMAN 87 CNTR /~ ~ e'rX O, Famllon <4 148 KACHELRIESS 97 ASTR D, neutron star cooling <3 x 10-4 90 138 8RYMAN 86B RVUE /~ ~ eX 0. Famllon <(o.s-8) x lO -3 149KEIL 97 ASTR SN 1987A <1. x 10-10 90 0 139 EICHLER 86 SPEC t~+ ~ e+X O, Famlion < 0.018 150 RAFFELT 95 ASTR D, red giant <2.6 x 10-6 90 140 JOOIDIO 86 SPEC ta + ~ e+X O. Fatal• < 0.010 151 ALTHERR 94 ASTR D, red giants, white 141 BALTRUSAIT..s MRK3 ~- ~ IX O. Famllon dwarfs 142 DICUS 83 COSM v(hvy) --* v(light)X 0 < 0.01 WANG 92 ASTR D, white dwarf < 0.03 WANG 92c ASTR D, C-O burning 130 BOBRAKOV 91 searched for anomalous magnetic interactions between polarized elec- 152 BERSHADY 91 ASTR D, K, trons expected from the exchange of a massless pseudoscalar boson (at• A limit none 3-8 Intergalactic light ~e < 2 x 10-4 (95%CL) is found for the effective anomalous magneton parametdzed <10 153 KIM 91C COSM D, K, mass density of as Xe( GF /81rv/2)1/2. the universe, super- symmetry 131ALBRECHT 90E limits are for B 0" ~ txO)/B('r ~ iv'P). Valid for mxo < 100 154 RAFFELT 91B ASTR D,K, SN 1987A MeV. The limits rise to 7.1% (for/~), 5.0% (for e) for mXo = 500 MeV. < 1 x 10-3 155 RESSELL 91 ASTR K, Intergalactic light 132ATIYA 90 limit is for mXO = 0. The limit B < 1 x 10-8 holds for mxo < 95 MeV. none 10-3-3 BURROWS 90 ASTR D,K, SN 1987A For the reduction of the limit due to finite lifetime of X 0, see their Fig. 3. 156 ENGEL 90 ASTR D,K, SN 1987A 133BOLTON 88 limit corresponds to F > 3.1 x 109 GeV, which does not depend off the < 0.02 157 RAFFELT 9OD ASTR D, red giant chirality property of the coupling. < 1 x 10 -3 158 BURROWS 89 ASTR D,K, SN 1987A 134CHANDA 88 find v T < 10 MeV for the weak-triplet Hlggs vev. in GelminI-Roncadelll <(1.4-10) x 10-3 159 ERICSON 89 ASTR D,K, SN 1987A model, and v5 > 5.8 x 106 GeV in the slng!et MaJoron model. < 3.6 X 10-4 160 MAYLE 89 ASTR D,K, SN 1987A 135CHOI 88 used the observed neutrino flux from the supernova SN 1987A to exclude the <12 CHANDA 88 ASTR D, Sun neutrino MaJoron Yukawa coupling h in the range 2 x 10 -5 < h < 3 x 10 -4 for the 276 Gauge & Higgs Boson Particle Listings Axions (A ~ and Other Very Light Bosons < 1 x 10-3 RAFFELT 88 ASTR D,K, SN 1987A Invldble .40 (AxJon) Limits from Photon Coupling 161RAFFELT 880 ASTR red giant Limits are for the axion-two-photon coupling GA.7.7 defined by L = GA3,3,~AE.B. < 0.07 FRIEMAN 87 ASTR D, red giant Related limits from astrophysics can be found in the "invisible A 0 (Axion) Mass Limits < 0.7 162 RAFFELT 87 ASTR K, red giant from Astrophysics and Cosmology" section. < 2-5 TURNER 87 COSM K, thermal production VALUE(GeV- 1) CL.~.~__~ DOCUMENTID COMMENT < O.O1 163 DEARBORN 86 ASTR D, red giant We do not use the following data for averages, fits. limits, etc. < 0.06 RAFFELT 86 ASTR D, red giant < 0.7 164RAFFELT 86 ASTR K, red giant <3.6 x 10 -7 95 169 CAMERON 93 mAo < 10-3 eV, < 0.03 RAFFELT 86B ASTR D, white dwarf optical rotation < 1 165 KAPLAN 85 ASTR K, red giant <6.7 x 10 -7 95 170 CAMERON 93 mAo < 10-3 eV, < 0.003-0.02 IWAMOTO 84 ASTR D, K, neutron star photon regeneration > 1 x 10-5 ABBOTT 83 COSM D,K, mass density of the <3.6 x 10 -9 99.7 171 LAZARUS 92 mAo < 0.03 eV universe <7.7 x 10 -9 99.7 171 LAZARUS 92 mAo= 0.03-O.11 eV > 1 • 10-5 DINE 83 COSM D,K, mass density of the universe <7.7 x 10-7 99 172 RUOSO 92 mAo < 10-3 eV < 0.04 ELLIS 830 ASTR D, red giant <2.5 x 10-6 173 SEMERTZIDIS 90 mAo < 7 x 10-4 eV > 1 x 10 -5 PRESKILL 83 COSM D,K, mass density of the universe 169 Experiment based on proposal by MAIANI 86. < O.1 BARROSO 82 ASTR D, red gia/lt 170Experiment based on proposal by VANBIBBER 87. < 1 166 FUKUGITA 82 ASTR D, stellar cooling 171 LAZARUS 92 experiment is based on proposal found in VANBIBBER 89. < 0.07 FUKUGITA 820 ASTR D, red giant 172RUOSO 92 experiment Is based on the proposal by VANBIBBER 87. 147 BORISOV 97 bound is on the axion-electron coupling gee < 1 x 10-13 from the photo- 173SEMERTZIDIS 90 experiment Is based on the proposal of MAIANI 86. The limit Is production of axloos off of electric fields In the outer layers of neutron stars. obtained by taking the noise amplitude as the upper limit. Limits extend to mAo = 148KACHELRIESS 97 bound is on the axion-electron coupling gee < 1 x 10-10 from the 4 x 10-3 where GA../.7 < 1 x 10-4 GeV-1. production of axions in strongly magnetized neutron stars. The authors also quote a stronger limit, gee < 9 x 10-13 which is strongly dependent on the stren~h of the magnetic field !n white dwarfs. Omit on Invisible .4o (Axlon) Electron Coupling 149KEIL 97 uses new measurements of the axial-vector coupling strength of nucleons, as well as a reanalysis of many-body effects and plon-emlssion processes In the core of the The limit Is for GAeeO/~A~/#3,5e in GeV -1, or equlvalenty, the dipole-dipole po- neutron star, to update limits on the Iovlsible-axion mass. 150RAFFELT 95 reexamined the constraints on axion emission from red giants due to the tential G4~e ((e' 1 . e'2) -3(o' 1 n) (it 2 . n))/r 3 where n=r/r. axlon-electron coupling. They improve on DEARBORN 86 by taking into proper account degeneracy effects in the bremsstrahlung rate. The limit comes from requiring the red The limits below apply to Invisible axion of m A < 10-6 eV. giant core mass at helium Ignition not to exceed Its standard value by more than 5% VALUE(GeV- 1) CL~_~ DOCUMENTID TECN COMMENT (0.025 solar masses). We do not use the following data for averages, fits, limits, etc. 151ALTHERR 94 bound is on the axion-electron coupling gee < 1.5 x 10 -13, from energy toss via axion emission. <5.3 x 10-5 66 174 NI 94 Induced magnetism 152 BERSHADY 91 searched for a line at wave length from 3100-8300 A expected from 23' <6.7 x 10 -5 66 174 CHUI 93 Induced magnetism decays of relic thermal axlons In intergalactic light of three rich clusters of galaxies. <3.6 x 10 -4 66 175 PAN 92 Torsion pendulum 153 KIM 91c argues that the bound from the mass density of the universe will change dras- <2.7 • 10 -5 95 174 BOBRAKOV 91 Induced magnetism tically for the supersymmetdc models due to the entropy production of saxion Iscalar <1,9 x 10-3 66 176WINELAND 91 NMR component In the axionic chlral multiplet) decay. Note that It Is an upperbound rather <8.9 • 10 -4 66 175 RITTER 90 Torsion pendulum than a Iowerbound. <6.6 x 10-5 95 174VOROBYOV 88 Induced magnetism 154 RAFFELT 91B argue that previous SN 1987A bounds must be relaxed due to corrections to nucleon bremsstrahlung processes. 174These experiments measured Induced magnetization of a bulk material by the spin- 155 RESSELL 91 uses absence of any Intracluster line emission to set limit. dependent potential generated from other bulk material with aligned electron spins, 156ENGEL 90 rule out 10-10 ,~ gAN ~, 10-3, which for a hadronic axion with EMC where the magnetic field is shielded with superconductor. 175These experiments used a torsion pendulum to measure the potential between two bulk motivated axlon-nucleon couplings corresponds to 2.5 x 10-3 eV ~ mAo <,~ 2.5 x matter objects where the spins are polarized but without a net magnetic field in either 104 eV. The constraint is loose In the middle of the range, Le. for gAN ~ 10-6. of them. 157RAFFELT 90D Is a re-analysis of DEARBORN 86. 176WlNELAND 91 looked for an effect of bulk matter with aligned electron spins on atomic hyperfine splitting using nuclear magnetic resonance. 158The region mAo ?~ 2 eV is also allowed. 159ERICSON 89 considered various nuclear corrections to axlon emlsalon in a supernova core, and found a reduction of the previous limit (MAYLE 88) by a lame factor. Axlon Umlts from T-vlolatlng Medlum-Ranp Forces 160 MAYLE 89 limit based on naive quark model couplings of axlon to nucleons. Limit based The limit is for the coupling g in a -/'-violating potential between nucleons or nucleon on couplings motivated by EMC measurements is 2-4 times weaker. The limit from and electron of the form V= 8K~hm2p(c'.P) (r-~ -P ~r c ) e-mAcr/T= axlon-electron coupling is weak: see HATSUDA 880. 161 RAFFELT 880 derives a limit for the energy generation rate by exotic processes in helium- VALUE DOCUMENTID burning stars < 100 erg g-1 s- 1, which gives a firmer basis for the axion limits based on red giant cooling. We do not use the following data for averages, fits, limits, etc. 162RAFFELT 87 also gives a limit gA3' < I x 10-10 GeV -1. 177 YOUDIN 96 | 163DEARBORN 86 also gives a limit gA3" < 1.4 x 10-11 GeV- 1 177y O U D IN 9 6 compared the prec esslon frequencies of atomic 199 Hg and Cs when a large | mass is positioned near the ceils, relative to an applied magnetic field. See Fig. 3 fo/" 164 RAFFELT 86 gives a limit EA"/ < 1.1x 10-10 GeV- 1 from red gis nts and < 2.4 x 10-9 their limits. I GeV -1 from the sun. 165KAPLAN 85 says mAo < 23 eV is allowed for a special clloice of model parameters. REFERENCES FOR Searchesfor Axlo.s (A~ and Other Very LII;ht Bosons 166FUKUGITA 82 gives a limit gA3, < 2.3 • 10 -10 GeV-1. ADLER 97 PRL 79 2204 S. Adler+ (BNL 787 Collab.) AHMAD 97 PRL 70 E18 I. Ahmad+ (APEX Collab.) BORISOV 97 JETP83 868 +Gdshinia (MOSU) Starch for l~.llc hwMbie DEBOER 97C JP G23 L85 F.W.N. de Boer+ KACHELRIESS 97 PR D56 1313 +Wilke, Wunner (BOCH) Limits are for [GA.7.7/mAO)2pA where GA~.7 denotes the axion tv~-photon coupling, KEfL 97 PR D56 2419 W. Keif+ KITCHING 97 PRL 79 4079 P. Kitchins+ (gNL 787 Cdlab.) Lin t = G~'T?(PAFI~uk'I~u = GA.7~d)AE.B, and PA Is the axlon energy density near LEINBERGER 97 PL B394 16 U. Leinberger+ (ORANGE Collab.) the earth. ADLER 96 PRL 76 1421 +Atiya, ChlanK, Fraek, Halg[erty. Kycia+ (BNL 787 Collab.) VALUE CL~ DOCUMENTID TECN COMMENT AMSLER %B ZPHY C70 219 +Armstrong,Baker, Barnett+ (Crystal Barrel Collab.) GANZ % PL B389 4 +Beer, Balanda+ (GSI, HELD, FRAN, JAGL. MPIH) We do not use the following data for averages, fits, limRs, etc. GUENTHER % PR D54 3641 +Hellmlg, Heusser, Hirrch+ (MPIH, 5A550) KAMEL % PL 0366 291 (SHAMS) <2 x 10-41 167 HAGMANN 90 CNTR mAo = MITSUI % EPL 33 111 +Maki, Asai, hhiraki+ (TOKY) YOUDIN % PRL 77 2170 +Krause, Jagannathan, Hu.ter+ (AMHT, WASH) (5.4-5,9)10-6 eV ALTMANN % ZPHY C65 221 +Declais, v. Feilit.~ch+ (MUNT, LAPP, CPPM} <1.3 x 10-42 95 168WUENSCH 89 CNTR mAo = (4.5-10.2)10 -6 BALEST 95 PR D51 2053 +Cho, Ford, Johnsoa+ (CLEO Collab.) eV BASSOMPIE... 95 PL 0355 584 Balaompierre, Bologna+ (LAPP, LCGT, LYON) <2 x 10-41 95 168WUENSCH 89 CNTR mAo = MAENO 95 PL 0351 574 +Fujlkawa, Kataoka, Ni~hihara+ (TOKY) RAFFELT 95 PR D51 1495 +Weiss (MPIM, MPIA) (11.3-16.3)10 -6 eV SKALSEY 95 PR D51 6292 +Collti (MICH) TSUNODA 95 EPL 30 273 +Nakamura, Orito, Minowa (TOKY) 167 HAGMANN 90 experiment is based on the proposal of SIKIVIE 83. ADACHI 94 PR A49 3201 +Chiba, Hirose, Nagayama+ (TMU) 168WUENSCH 89 looks for condensed axions near the earth that could be converted to ALTHERR g4 ASP 2 175 +petiq~rard, del Rio GaztelurrutJa (CERN, LAPP, DFAB) photons in the presence of an intense electromagetlc field via the Pdmakoff erect, fol- AMSLER r PL B333 271 +Armstrong,Ould-Saada+ (Crystal Barrel Collab.) ASAI 94 PL 0323 90 +Shlgekuni, Sanuld, Odto (TOKY) lowing the proposal of SIKIVIE 83. The theoretical prediction with [GA./3,/mAo] 2 = MEIJERDREES 94 PR 049 4937 Meijel Drees, Waltham+ (BRCO. OREG, TRIU) NI 94 PhysicaB194 153 +Chui, Pan, Chenl[ (NTHU) 2 x 10-14 MeV-4 (the three generation DFSZ model) and PA = 300 MeV/cm 3 that VO 94 PR C49 1551 +Kdly, Wohn, Hill+ (ISU, LBL, LLNL, UCD) makes up galactic halos gives (GA.r3,/mAo) 2 PA = 4 x 10 -44. Note that our definition ATIYA 93 PRL 70 2521 +Chiang, Frank, Hqg[erty, Ito+ (BNL 787 Collab.) AlSO 93C PRL"71 305 (erratum) Atiya, Chian|, Frank, Hauerty, Ito+ (BNL 787 Collab.) of GA3,3, is (1/47r) smaller than that of WUENSCH 89. ATIYA 93B PR D48 R1 +Chia,g, Frank, Hal~erty, Ito+ (BNL 787 Collab.) BASSOMPIE.., 93 EPL 22 239 Bassomplerre, Bologna+ (LAPP, TORI, LYON) BECK 93 PRL 70 2853 +Bensch, Bockholt, Heusser, Hirsch+(MPIH, KIAE, SASSO) 277 See key on page 213 Gauge & Higgs Boson Particle Listings Axions (A ~ and Other Very Light Bosons CAMERON 93 PR D47 3707 +Cantatore. Melisdnos+ (ROCH,BNL, FNAL, TRST) FRIEMAN 87 PR D36 2201 +Dimopoulos.Turner (SLAC, STAN, FNAL, EFI) CHUI 93 PRL 71 3247 +Ni (NTHU) GOLDMAN 87 PR D36 1543 +Hallin, Hoffman+ (LANL, CHIC, STAN, TEMP) MINOWA 93 PRL 71 4120 +lnoue, Asanuma, tmamura (TOKY) KORENCHE.. 87 SJNP 46 192 K~enchenko. Kostia. Mzhav~ya+ (JINR ) NG 93 PR D48 2941 (AST) Translated from YAF 46 313. TANAKA 93 PR D48 5412 +Ejiri (OSAK) MAIER 87 ZPHY A326 527 +Bauer, Bri68mann, Carstanjea+ (STUT, GSI) ALLIEGRO 92 PRL 68 273 +Campagnari+ (BNL. FNAL, PSI, WASH, YALE) MILLS 87 PR D36 707 +Levy (BELL) ATIYA 92 PRL 69 733 +Chiang, Frank. Ha68erty, Ito+ (BNL, LANL, PRIN, TRIU) RAFFELT 87 PR D36 2211 +Dearborn (LLL. UCB) BERNATOW... 92 PRL 69 2341 Bernatowicz, Brannon, Brazzle, Cowsik+ (WUSL, TATA) RIORDAN 87 PRL 59 755 +Krasny, Lang. Barbaro. Bodek+ (ROCH, CIT+) BLUEMLEIN 92 IJMP A7 3835 +Brunner, Grabosch+ (BERL, BUDA, JINR, SERP) TURNER 87 PRL 59 2489 (FNAL, EFI) HALLIN 92 PR D45 3955 +Calapr McPherson, Saettier (PRIN) VANBIBBER 87 PRL 58 759 Van Bibber, Dagdeviren, Koonin+(LLL, CIT, MIT, STAN) HENDERSON 92C PRL 69 1733 +Asoka-Kumar. Greenberg, Lynn+ (YALE. BNL) VONWlMMER..JB7 PRL 59 266 yon Wlmme~per|, Connell, Hoernie, Sideras~Heddad(WlTW) HICKS 92 PL B276 423 +AJburger (OHIO. BNL) ALBRECHT 86D PL B179 403 +Binder. Boeckmann+ (ARGUS Coi]ab.) LAZARUS 82 PRL 69 2333 +Smith, Cameron, Melissinos+ (BNL, ROCH, FNAL) BADIER 86 ZPHY C31 21 +BOmwad, Boucrot, Cailot+ (NA3 Colieb.) MEIJERDREES 82 PRL 68 3845 Meijer Drees, Waltham+ (SINDRUM I Coilab.) BOWCOCK 86 PRL 56 2576 +Giles. Hassard, Kieoshita+ (CLEO Coilab.) PAN 92 MPL 7 1287 +Ni. Chen (NTHU) BROWN 86 PRL 57 2101 + (FNAL, WASH, KYOT, KEK, COLU, STON, SACL) RUOSO 92 ZPHY C56 505 +Cameron, Cantatore+ (ROCH, BNL. FNAL, TRST) BRYMAN 86B PRL 87 2787 +Clifford (TRIU) SKALSEY 92 PRL 68 456 +Kolata (MICH. NDAM) DAVIER 86 PL B180 295 +Jeanjean. Nguyen Ngoc (LALO) WANG 92 MPL A7 1497 (ILL) DEARBORN 86 PRL 56 26 +Schramm, Steigman (LLL, CHIC, FNAL, BART) WANG 92C PL 8291 97 (ILL) EICHLER 86 PL B175 101 +Felawke, Kraus, Niebuhr+ (SINDRUM Coilab.) WU 92 PRL 69 1729 +Asoka-Kumar, Greenber~ Henderson+(BNL, YALE, CUNY) HALLIN 86 PRL 57 2105 +Calparice, Ounford, McDonald (PRIN) AKOPYAN 91 PL 8272 443 +Atoyan, Gnlnenko, Sukhov (INRM) JODtDtO 86 PR O34 1967 +Balke, Carr, GidaI, Shinsky+ (LBL, NWES, TRIU) ASAI 91 PRL 66 2440 +Orito, yoshimura, Haga (ICEPP) Also 88 PR D37 237 erratum Jodidio,Balke. Can+ (LBL, NWES, TRIU) BERSHADY 91 PRL 66 1398 +Re~isell, Turner (CHIC. FNAL, EFI) KETOV 86 JETPL 44 146 +Klimov, Nikolaev, Mikeelyan+ (KIAE) BLUEMLEIN 91 ZPHY C51 341 +Brunner. Grabo~h+ (BERL. BUDA, JINR, SERP) Trandated from ZETFP 44 114. BOBRAKOV 91 JETPL 53 294 +Bodsov, Lasakov, Serebrov, Tal'daev, Trofimova (PNPI) KOCH 86 NE 96A 182 +Schult (JULI) Translated from ZETFP 53 283. KONAKA 86 PRL 57 659 +lmai, Kobayashi, Masaike, Miyake+ (KYOT, KEK) BROSS 91 PRL 67 2942 +Crider, PoNes, Voik, Errede, Wrbanek (FNAL, ILL) MAGERAS I~ PRL 56 2672 +Franzini. Tuts. Youssef+ (MPIM, COLU, STON) KIM 91C PRL 67 3465 (SEOUL) MAIANI 86 PL B175 359 +Petronzio, ZavatUnl (CERN) RAFFELT 91B PRL 67 2605 +Seckel (MPIM, BART) PECCEI 86 PL BZ72 435 +Wu, Yanaglda (DESY) RESSELL 91 PR D44 3001 (CHIC, FNAL) RAFFELT 86 PR D33 897 (MPIM) TRZASKA 91 PL B269 54 +Dejbakhsh, Durra, Li, Cormler (TAMU) RAFFELT 86B PL 166B 402 (MPIM) TSERTOS 91 PL B266 259 +Kienie, Judge, Schreckenbach (ILLG, GSI) SAVAGE 8bB PRL 57 178 +McKeown, Filippo~e, Mitchell (CIT) WALKER 91 APJ 376 51 +Steigman, Schramm, Olive+ (HSCA. OSU, CHIC, MINN) AMALDI 85 PL 153B 444 +Carbonl, Jonson, Thun (CERN) WIDMANN 91 ZPHY A340 209 +Bauer, ConnelL Maier, Major+ (STUT, GSI, STUTM) ANANEV 85 SJNP 4] 585 +Kalinina, Lushchlkov, Olshevsldi+ (JINR) WlNELAND 91 PRL 67 1735 +Bolilnger, H-~nzen. llano, Raizen (NBSB) Translated from YAF 41 912. ALBRECHT 90E PL B246 278 +Ehrliehmann, Harder, Krueger+ (ARGUS Coilab.) BALTRUSAIT,.. 85 PRL 55 1842 Boltrusaitis, Becker, Blaylock, Brown+ (Mark III Coitab.) ANTREASYAN 9OC PL B251 204 +Bortels, Besset, Bieler, Bienlein+ (Crystal Ball CoBa0.) BERGSMA 85 PL 1578 458 +Dorenbo~ch,Allaby, Amaldi+ (CHARM Coital..) ASANUMA 90 PL 8237 588 +Min~a, Tsukamoto, Ofito, Tsunoda (TOKY) KAPLAN 85 NP 8260 215 (HARV) ATIYA 90 PRL 64 21 +Chiang. Frank, Ha68erty. Ito, Kycia+ (BNL 707 Coltab.) IWAMOTO 84 PRL 53 1198 (UCSB, WUSL) ATIYA 908 PRL 65 1188 +Chiang, Frank, Ha68erty. Ito, Kycia+ (BNL 787 Collab.) YAMAZAKI 84 PRL 52 1089 +lsh[ka~.~, Taniguchi, Yamanake+ (INUS, KEK) BAUER 90 NIM BSO 300 +Briggmann, Carstanjen, Connell+ (STUT, VILL, GSI) ABBOTT 83 PL 120B 133 +Siklvie (BRAN, FLOR) BURROWS 9O PR D42 3297 +Ressell, Turner (ARIZ, CHIC, FNAL) ALAM 83 PR D27 1665 + (VAND, CORN, ITHA, HARV, OHIO, ROCH+) DEBOER 90 JPG 16 L1 de Boer. Lehmann, Steyaert (LOUV} CARBONI 83 PL 123B 349 +Dahme (CERN, MUNI) ENGEL 90 PRL 65 960 +Secke4, Hayes (BART, LANL) CAVAIGNAC 83 PL 121B 193 +Hoummada, Koang, Ost+ (ISNG, LAPP) GNINENKO 9O PL B237 287 +Klubakov, Poblaguev, Postoev (INRM) DICUS 83 PR D28 1778 +Teplitz (TEXA, UMD} GUO 90 PR O41 Z924 +Kaplan, Aide+ (NIU, LANL, ENAL, CASE, TEXA) DINE 83 PL 1208 137 +Fischler (IAS, PENN) HAGMANN 90 PR D42 1297 +Sikivie, Sultivan, Tanne~" (FLOR) ELLIS g3B NP 8223 252 +OLive (CERN) JUDGE 90 PRL 65 972 +Krusche, Schreckenbach,Tsertos, Kienle (ILLG, GSI) FAISSNER 83 PR D28 1198 +Heinrics, Pzeust~er, Samm (AACH) RAFFELT 9OC PRPL 198 1 (MPIM) FAISSNER 838 PR D28 1787 +Frenzel, Heierigs. Preussger+ (AACH3) RAFFELT 90D PR D41 1324 (MPIM) FRANK 838 PR D28 1790 + (LANL, YALE, LBL, MIT, SACL, SIN, CNRE, BERN) RITTER 90 PR D42 977 +Goidblum, Ni, Gillies, Speake (VIRG) HOFFMAN 83 PR D28 660 +Frank, MJschke, Moir, Schardt (LANL, ARZS) SEMERTZlDIS 90 PRL 64 2988 +Cameron, Cantatoee+ (ROCH, BNL, FNAL, TRST) NICZYPORUH 83 ZPHY C17 197 +Jakubowski. Zeludzlewicz+ (LENA Coilab.) TSUCHIAKI 90 PL B236 81 +Orito, Yoshida, Minowa (ICEPP) PRESKILL 83 PL 120B 127 +Wise, Wilczek (HARV, UCSBT) TURNER 9() PRPL 197 67 (ENAL) SIKIVIE 83 PRL 51 1415 (FLOR) BARABASH 80 PL B223 273 +Kuzmlnov. Lobashev. N~lkov+ (ITEP, INRM) Also PRL 52 695 erratum Sikivie (FLOR) BINI 89 PL B221 99 +Fazzini, Glannatiempo, Poui , SoBa+(FIRZ, CERN, AARH) ALEKSEEV JETP 55 591 +Kartam~hev. Makarin+ (KIAE) BURROWS 89 PR D39 1020 +Turner, Briekmann (ARIZ, CHIC, FNAL, BOCH) Translated from ZETF 82 1007. Also 88 ALEKSEEV 82B JETPL 36 116 +Kalieiea. Kruglov, Kulihov+ (MOSU, JINR) PRL 60 1797 Turner (FNAL, EFI) Trandated from ZETFP 36 94. DEBOER 89B PRL 62 2639 de Boer, van Dantzig (ANIK) ASANO 82 PL 113B 195 +Kikutani, Kurokawa, M[yachJ+(KEK, TOKY, INUS, OSAK) ERICSON 89 PL B219 507 +Mathlot (CERN. IPN) BARROSO 82 PL 116B 247 +Branco (LISB) FAISSNER 59 ZPHY C44 557 +HeindKs.Preussger, Reitz, Saturn+ (AACH3. BERL, PSI) DATAR 82 PL 114B 63 +Baba, Betigerl. Singh (BHAB) FISHER 89 PL 8218 257 +Boehm. Bovet, Egger+ (CIT, NEUC, PSI) EDWARDS 82 PRL 48 903 +Partridge, Peck, Porter+ (CryStal Ball Cofiab.) FOX 89 PR C39 288 +Kemper. Cottle, Zingatell[ (FSU) FETSCHER 82 JPG 0 L147 (ETH) MAYLE 89 PL 8219 515 +Wilt,on, E0is+ (LLL. CERN, MINN, FNAL, CHIC, OSU) FUKUGITA 82 PRL 48 1522 +Watamura, YosMmura (KEK) Also 08 PL B203 188 Mayle. Wilson+ (LLL, CERN, MINN, FNAL, CHIC, OSU) FUKUGITA 02B PR D26 1840 +Watamura, Yoshlmura (KEK) MINOWA 09 PRL 62 1091 +Orito, Tlsuchieki, Tlsukamoto (ICEPP) LEHMANN 82 PL 1158 270 +Lesquoy. Muller. Zylberajch (SACL) ORITO 89 PRL 63 597 +Yoshimura, Haga, Minow~, Tsuchiaki (ICEPP) RAFFELT 82 PL 119B 323 +Stodolsky (MPIM) PERKINS 89 PRL 62 2638 (OXF) SIVERTZ 82 PR D26 717 +Lee-Franzinl,Horstkotte+ (CUSB Collab.) TSERTOS 59 PR D40 1397 +KozhuharOV,Armbtuster. Kienle+ (GSI, ILLG) VERGADOS 82 PL 1098 96 (EERN) VANBIBBER 89 PR D39 2089 Van Bibber. Mclntyre, Moeris, Raffelt (LLL, TAMU. LBL) ZEHNDER 82 PL 1108 419 +Gabathuler, Vuilleumier (ETH, SIN. CIT) WUENSCH 89 PR D40 3153 +De Panfilis-Wuensch,Semertzidis+ (ROCH, BNL, FNAL) ASANO 818 PL 107B ]59 +Kikutanr, Kurokawa, Miyachi+(KEK, TOKY, INUS, OSAK) Also 87 PRL 59 539 De Panfllis, Melissinos, Mo~kewitz+ (ROCH, BNL. FNAL) BARROSO 81 PL 106B 91 +Mukhopadh~y (SIN) ALSTON-... 00 PRL 60 3928 Alston-Garnjost,DoughertT+ (LBL, MTHO, UNM) FAISSNER 81 ZPHY CIO 95 +Frenzd, Grimm, Hand, Hoffman+ (AACH3) AVIGNONE 80 PR D37 618 +Boktash, Barker, Calapdce+(PRIN, SCUC, ORNL, WASH) FAISSNER 818 PL 105B 234 +Frenzel, Helmigs, Preussler+ (AACH3) BJORKEN 80 PR D38 3375 +Eckiend, Nelson, Abashlan+ (FNAL, SLAC. VPI) KIM 81 PL 10SB 55 +Stature (AACH3) BLINOV 88 SJNP 47 563 +Bondar. Bokin, Vorobyev, Groshev+ (NOVO) VUILLEUMIER 01 Translated from YAF 47 889. PL 101B 341 +Boehm, Hahn, Kwon+ (CIT, MUNI) BOLTON 88 PR D38 2077 +Cooper, Frank, Hallin+ (LANL, STAN, CHIC, TEMP) ZEHNDER 81 PL 1048 494 (ETH) Also 86 PRL 56 2461 Bolton, Bowman, Cooper+ (LANL, STAN. CHIC, TEMP) FAISSNER 8O PL %B 201 +Frenzeh HelndKs, Preuss~er, Samm+ (AACH3) AlSo 86 PRL 57 3241 Grosnick. Wright. Boiton+ (CHIC, LANL, STAN, TEMP) JACQUES 80 PR D21 1206 +Kalelkar, Miller, Piano+ (RUTG. STEV, COLU) CHANDA 85 PR D37 2714 +Nieve~, Pal (UMD, UPR. MASA) SOUKAS 80 PRL 44 564 +Wanderer, Weng+ (BNL. HARV, ORNL. PENN) CHOI 88 PR D37 3225 +KIm, Kim. Lain (JHU) BECHIS 79 PRL 42 1511 +Dombeck+ (UMD, COLU, AFRR) CONNELL 89 PRL 60 2242 +peafick, Hoernie, Sideras-Heddad, Sellschop (WlTW) CALAPRICE 79 PR D20 2708 +Dunford, Kouzes, Miller+ (PRIN) DATAR 88 PR C37 250 +ForBer, Gales, Hourani+ (IPN) COTEUS 79 PRL 42 1438 +Diesburg, Fine. Lee, Sokolsky+ (COLU, iLL, BNL) DEBOER 88 PRL 61 1274 de Boer, van Dantzi8 (ANIK) DISHAW 79 PL 85B 142 +Diamant-Berger, Faessler, Lie+ (SLAC, CIT) Also 89 ZHITNITSKII 79 SJNP 29 517 +Skovpen (NOVO) PRL 62 2644 erratum de Boer. van Dantzig (ANIK) Translated from YAF 29 1001. Aim 89 PRL 62 2638 Perkins (OXF) ALIBRAN 78 PL 74B 134 +Armenise, Arnold, Bortley (GargamelJe Collab.) AlSO 89B PRL 62 2639 de Boer, van Dantzig (ANIK) ASRATYAN 788 PL 79B 497 +Epstein, Fakhrutdlnov+ (ITEP, SERP) DEBOER 88C JPG 14 LL31 de Boer, Deutsch, Lehma,n. Ptleels, SteFaerL (LOUV) BELLDTTI 78 PL 76B 223 +Ftofinl. Zanott~ (MtLA) DOEHNER 88 PR D38 2722 +Last, Arnold, Freedman.Dubbers (HEIDP,ANL, ILLG) BOSETTI 78B PL 748 143 +Deden, Deut~hmann, Fritze+ (BEBC Collab.) DOI 88 PR D37 2575 +Kotanl, Takesugi (OSAK) DICUS 78C PR D18 1829 +Koib, TelWitz, Wagoner (TEXA, VPI. STAN) EL-NADI 88 PRL 61 1271 +Bodawy (CAIR) DONNELLY 78 PR D18 1607 +Freedman,Lytel, Peccei, Schwartz (STAN) FAISSNER 88' ZPHY C37 231 +Helnrigs, Preus~er, Reitz, Saturn+ (AACH3. BERL, SIN) Also 76 PRL 37 315 Reines, Gurr, Sober (UCI) HATSUDA 88B PL B203 469 +Yoshimura (KEK) Also 74 PRL 33 179 Gurr. R~nes, Sobel (UCI) LORENZ 88 PL 8214 10 +Mageras. Stiegler, Huszar (MPIM. PSI) HANSL 78D PL 74B 139 +Holder, Hnobloch, May, Paar+ (CDHS Collab.) MAYLE 88 PL B203 188 +Wilson+ (LLL, CERN, MINN, FNAL. CHIC, OSU) MICELMAC.. 78 LNC 21 441 Micelmacher, Pontecorvo (JINR) PICCIOTTO 88 PR D37 1131 +Ahmad, Britton, Bryman, Clifford+ (TRIU, CNRC) MIKAELIAN 78 PR D18 3605 (FNAL. NWES) RAFFELT 08 PRL 60 1793 +Seeker (UCB. LLL, UCSC) SATO 78 PTP 60 1942 (KYOT) RAFFELT 88B PR D37 549 +Dearborn (UCB. LLL) VYSOTSKII 78 JETPL 27 502 +Zeldovich, Khlopov, Ckechetkin (ASCI) SAVAGE 88 PR D37 1234 +Filippone, Mitchell (CIT) TransJated from ZETFp 27 533. TSERTOS 88 PL B207 273 +Kozhuharov,Armb~uster, Kienie+ (GSh ILLG) YANG 78 PRL 41 523 (MASA) TSERTOS 008 ZPHY A331 303 +Kozhuharov,Armbeuster, Kieoie+ (GSh ILLG) PECCEI 77 PR D16 1791 +Quinn (STAN, SLAC) VANKLINKEN 88 PL 8205 223 van Kllnken, Meiring, de Boer, Schaafsma+ (GRON. GSI) Also 77R PRL 38 1440 Peccel, Quinn (STAN, SLAC) VANKUNKEN 88B PRL 60 2442 van Klieken (GRON) REINES 76 PRL 37 315 +Gurr, Sobel (UCl) VONWlMMER.~8 PRL 60 2443 yon Wimmersperg (BNL) GURR 74 PRL 33 178 +Reiees, Sobel (UCI) VOROBYOV 88 PL B208 I46 +Gitarts (NOVO) ANAND 53 PRSL A22 183 AViGNONE 87 AlP Conf. 3987 +Brodzinskl, Mitey, Reeves (SCUC, PNL) AlP Conf. Proc. Salt Lake City, UT CALDWELL 87 PRL 59 419 +Eisberg, Grumm, Witherefi+ (UCSB, LBL) OTHER RELATED PAPERS DRUZHININ 87 ZPHY C37 1 +DuMovie, Eidelman, Goiubev+ (HOVO) ELLIOTT 87 PRL $9 1649 +Hahn, Moe (UCI) SREDNICKI 85 NP B260 689 (UCSB) FISHER 87 PL BL92 460 +Boehm, Bovet, F.gger+ (CIT, NEUC. SIN) BARDEEN 78 PL 748 229 +Tye (FHAL)