Probing the Minimal Length Scale by Precision Tests of the Muon G − 2

Total Page:16

File Type:pdf, Size:1020Kb

Probing the Minimal Length Scale by Precision Tests of the Muon G − 2 Physics Letters B 584 (2004) 109–113 www.elsevier.com/locate/physletb Probing the minimal length scale by precision tests of the muon g − 2 U. Harbach, S. Hossenfelder, M. Bleicher, H. Stöcker Institut für Theoretische Physik, J.W. Goethe-Universität, Robert-Mayer-Str. 8-10, 60054 Frankfurt am Main, Germany Received 25 November 2003; received in revised form 20 January 2004; accepted 21 January 2004 Editor: P.V. Landshoff Abstract Modifications of the gyromagnetic moment of electrons and muons due to a minimal length scale combined with a modified fundamental scale Mf are explored. First-order deviations from the theoretical SM value for g − 2 due to these string theory- motivated effects are derived. Constraints for the fundamental scale Mf are given. 2004 Elsevier B.V. All rights reserved. String theory suggests the existence of a minimum • the need for a higher-dimensional space–time and length scale. An exciting quantum mechanical impli- • the existence of a minimal length scale. cation of this feature is a modification of the uncer- tainty principle. In perturbative string theory [1,2], Naturally, this minimum length uncertainty is re- the feature of a fundamental minimal length scale lated to a modification of the standard commutation arises from the fact that strings cannot probe dis- relations between position and momentum [6,7]. Ap- tances smaller than the string scale. If the energy of plication of this is of high interest for quantum fluc- a string reaches the Planck mass mp, excitations of the tuations in the early universe and inflation [8–16]. string can occur and cause a non-zero extension [3]. The incorporation of the modified commutation re- Due to this, uncertainty in position measurement can lations into quantum theory is not fully consistent in never become smaller than lp = h/m¯ p.Forareview, all approaches. We will follow the propositions made see [4,5]. in [17]. Although a full description of quantum gravity is In our approach, the existence of a minimal length not yet available, there are general features that seem scale grows important for collider physics at high en- to go hand in hand with promising candidates for such ergies or for high precision measurements at low ener- a theory: gies due to the lowered value of the fundamental scale Mf . This new scale is incorporated through the central idea of large extra dimensions (LXDs). The model of LXDs which was recently proposed in [18–22] might E-mail address: [email protected] indeed allow to study first effects of unification or (U. Harbach). quantum gravity in near future experiments. Here, the 0370-2693/$ – see front matter 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.physletb.2004.01.051 110 U. Harbach et al. / Physics Letters B 584 (2004) 109–113 hierarchy-problem is solved or at least reformulated arbitrarily small Compton wavelengths λ = 2π/k and in a geometric language by the existence of d com- that arbitrarily small scales could not be resolved pactified LXDs in which only gravitons can propa- anymore. gate. The standard model particles are bound to our To incorporate this behaviour, we assume a rela- 4-dimensional sub-manifold, often called our 3-brane. tion k = k(p) between p and k which is an uneven This results in a lowering of the Planck scale to a new function (because of parity) and which asymptotically fundamental scale Mf and gives rise to the exciting approaches 1/Lf . Furthermore, we demand the func- possibility of TeV scale GUTs [23]. tional relation between the energy E and the frequency In this scenario the following relation between the ω to be the same as that between the wave vector k and four-dimensional Planck mass mp and the higher- the momentum p. A possible choice for the relations is dimensional Planck mass Mf can be derived: γ = 1/γ p 2 = d d+2 Lf k(p) tanh , (2) mp R M . (1) M f f The lowered fundamental scale would lead to a γ = 1/γ E vast number of observable phenomena for quantum Lf ω(E) tanh , (3) Mf gravity at energies in the range Mf . In fact, the non- observation in past collider experiments of these pre- with a real, positive constant γ . dicted features gives first constraints on the parameters In the following we will study an approximation, of the model, the number of extra dimensions d and namely the regime of first effects including the orders (p/M )3. For this purpose, we expand the function in the fundamental scale Mf [24,25]. On the one hand, f this scenario has major consequences for cosmology a Taylor series for small arguments. and astrophysics such as the modification of inflation Because the exact functional dependence is un- in the early universe and enhanced supernova-cooling known, we assume an arbitrary factor α in front of the 3 due to graviton emission [20,26–29]. On the other order (p/Mf ) -term. Therefore the most general re- hand, additional processes are expected in high-energy lations for k(p) and ω(E) which we will use in the collisions [30,31]: production of real and virtual gravi- following should be tons [32–36] and the creation of black holes at energies p p 3 that can be achieved at colliders in the near future [37– Lf k(p) ≈ − α , (4) Mf Mf 43] and in ultra high energetic cosmic rays [44]. One also has to expect the influence of the extra dimen- 3 ≈ E − E sions on high precision measurements. The most ob- Lf ω(E) α , (5) Mf Mf vious being the modification of Newton’s law at small 1 3 distances [45–47]. Of highest interest are also modifi- p(k) ≈ kLf + α(kLf ) , (6) cations of the gyromagnetic moment of Dirac particles Mf which promises new insight into non-standard model 1 3 E(ω) ≈ ωLf + α(ωLf ) , (7) couplings and effects [48–53]. Mf In this Letter we study implications of these exten- with α being of order one, in general negative values sions in the Dirac equation without the aim to derive of α cannot be excluded. them from a fully consistent theory. Instead we will This yields to 3rd order analyse possible observable modifications that may arise by combining the assumptions of both extra di- 1 ∂p p 2 mensions and a minimal length scale. ≈ 1 + 3α . (8) h¯ ∂k M In order to implement the notion of a minimal f length Lf , let us now suppose that one can increase The quantisation of these relations is straightfor- the momentum p arbitrarily, but that the wave number ward. The commutators between kˆ and xˆ remain in k has an upper bound. This effect will show up the standard form: when p approaches a certain scale M . The physical f [ˆ ˆ]= interpretation of this is that particles could not possess x,k iδij . (9) U. Harbach et al. / Physics Letters B 584 (2004) 109–113 111 Inserting the functional relation between the wave the generalised uncertainty principle, we start with the vector and the momentum then yields the modified relation commutator for the momentum. With the commutator ˆ = 0 i ˆ + relation E(ω) γ γ pi(k) m . (19) ˆ ∂A Including the altered momentum wave vector relation x,ˆ A(k) =+i , (10) ˆ ˆ ∂k p(k) from Eq. (16), this yields again Eq. (18) with the modified momentum operator the modified commutator algebra now reads ˆ − = ∂p p(/ k) m ψ 0. (20) [ˆx,pˆ]=+i . (11) ∂k This equation is Lorentz invariant by construction. This results in the generalised uncertainty relation Since it contains—in position representation—3rd order derivatives in space coordinates, it contains 1 ∂p px . (12) 3rd order time-derivatives too. In our approximation, 2 ∂k we can solve the equation for a single order time With the approximations (4)–(7), the results of derivative by using the energy condition E2 = p2 + Ref. [8] are reproduced up to the factor α: m2. This leads effectively to a replacement of time derivatives by space derivatives: pˆ2 [ˆx,pˆ]≈ih¯ 1 + 3α (13) ˆ 3 ˆi ˆ + 2 2 ˆ αE ˆ p pi m Mf h¯ωˆ ≈ E − = E 1 − α . (21) M2 M2 giving the generalised uncertainty relation f f Inserting the modified E(ω)ˆ and p(k)ˆ and keeping 1 ˆp2 px h¯ 1 + 3α . (14) only derivatives up to 3rd order, we obtain the follow- 2 2 Mf ing expression of the Dirac equation: Quantisation proceeds in the usual way from the 2 ˆi ˆ + 2 0 i ˆ m h¯ k ki m commutation relations. Focusing on conservative po- ω|ψ ≈γ γ ki + 1 − α |ψ . h¯ M2 tentials in quantum mechanics we give the operators f (22) in the position representation which is suited best for this purpose: The task is now to derive the modifications of the anomalous gyromagnetic moment due to the existence ˆ xˆ = x, k =−i∂x, of a minimal length. Therefore we assume as usual pˆ =ˆp(k),ˆ (15) the particle is placed inside a homogeneous and static magnetic field B. Regarding the energy levels of an yielding the new momentum operator electron the magnetic field leads to a splitting of the energetic degenerated values which is proportional to p(ˆ k)ˆ ≈−ih¯ 1 − αL2 ∂2 ∂ . (16) f x x the magnetic field B and the gyromagnetic moment g. In ordinary relativistic quantum mechanics the Since the energy of the particle in the field is not Hamiltonian of the Dirac particle is1 modified (see (18)) there is no modification of the splitting as one might have expected from the fact that ˆ = = 0 i + H ih∂¯ 0 γ ihγ¯ ∂i m .
Recommended publications
  • An Introduction to Effective Field Theory
    An Introduction to Effective Field Theory Thinking Effectively About Hierarchies of Scale c C.P. BURGESS i Preface It is an everyday fact of life that Nature comes to us with a variety of scales: from quarks, nuclei and atoms through planets, stars and galaxies up to the overall Universal large-scale structure. Science progresses because we can understand each of these on its own terms, and need not understand all scales at once. This is possible because of a basic fact of Nature: most of the details of small distance physics are irrelevant for the description of longer-distance phenomena. Our description of Nature’s laws use quantum field theories, which share this property that short distances mostly decouple from larger ones. E↵ective Field Theories (EFTs) are the tools developed over the years to show why it does. These tools have immense practical value: knowing which scales are important and why the rest decouple allows hierarchies of scale to be used to simplify the description of many systems. This book provides an introduction to these tools, and to emphasize their great generality illustrates them using applications from many parts of physics: relativistic and nonrelativistic; few- body and many-body. The book is broadly appropriate for an introductory graduate course, though some topics could be done in an upper-level course for advanced undergraduates. It should interest physicists interested in learning these techniques for practical purposes as well as those who enjoy the beauty of the unified picture of physics that emerges. It is to emphasize this unity that a broad selection of applications is examined, although this also means no one topic is explored in as much depth as it deserves.
    [Show full text]
  • Astro 282: Problem Set 1 1 Problem 1: Natural Units
    Astro 282: Problem Set 1 Due April 7 1 Problem 1: Natural Units Cosmologists and particle physicists like to suppress units by setting the fundamental constants c,h ¯, kB to unity so that there is one fundamental unit. Structure formation cosmologists generally prefer Mpc as a unit of length, time, inverse energy, inverse temperature. Early universe people use GeV. Familiarize yourself with the elimination and restoration of units in the cosmological context. Here are some fundamental constants of nature Planck’s constant ¯h = 1.0546 × 10−27 cm2 g s−1 Speed of light c = 2.9979 × 1010 cm s−1 −16 −1 Boltzmann’s constant kB = 1.3807 × 10 erg K Fine structure constant α = 1/137.036 Gravitational constant G = 6.6720 × 10−8 cm3 g−1 s−2 Stefan-Boltzmann constant σ = a/4 = π2/60 a = 7.5646 × 10−15 erg cm−3K−4 2 2 −25 2 Thomson cross section σT = 8πα /3me = 6.6524 × 10 cm Electron mass me = 0.5110 MeV Neutron mass mn = 939.566 MeV Proton mass mp = 938.272 MeV −1/2 19 Planck mass mpl = G = 1.221 × 10 GeV and here are some unit conversions: 1 s = 9.7157 × 10−15 Mpc 1 yr = 3.1558 × 107 s 1 Mpc = 3.0856 × 1024 cm 1 AU = 1.4960 × 1013 cm 1 K = 8.6170 × 10−5 eV 33 1 M = 1.989 × 10 g 1 GeV = 1.6022 × 10−3 erg = 1.7827 × 10−24 g = (1.9733 × 10−14 cm)−1 = (6.5821 × 10−25 s)−1 −1 −1 • Define the Hubble constant as H0 = 100hkm s Mpc where h is a dimensionless number observed to be −1 −1 h ≈ 0.7.
    [Show full text]
  • Small Angle Scattering in Neutron Imaging—A Review
    Journal of Imaging Review Small Angle Scattering in Neutron Imaging—A Review Markus Strobl 1,2,*,†, Ralph P. Harti 1,†, Christian Grünzweig 1,†, Robin Woracek 3,† and Jeroen Plomp 4,† 1 Paul Scherrer Institut, PSI Aarebrücke, 5232 Villigen, Switzerland; [email protected] (R.P.H.); [email protected] (C.G.) 2 Niels Bohr Institute, University of Copenhagen, Copenhagen 1165, Denmark 3 European Spallation Source ERIC, 225 92 Lund, Sweden; [email protected] 4 Department of Radiation Science and Technology, Technical University Delft, 2628 Delft, The Netherlands; [email protected] * Correspondence: [email protected]; Tel.: +41-56-310-5941 † These authors contributed equally to this work. Received: 6 November 2017; Accepted: 8 December 2017; Published: 13 December 2017 Abstract: Conventional neutron imaging utilizes the beam attenuation caused by scattering and absorption through the materials constituting an object in order to investigate its macroscopic inner structure. Small angle scattering has basically no impact on such images under the geometrical conditions applied. Nevertheless, in recent years different experimental methods have been developed in neutron imaging, which enable to not only generate contrast based on neutrons scattered to very small angles, but to map and quantify small angle scattering with the spatial resolution of neutron imaging. This enables neutron imaging to access length scales which are not directly resolved in real space and to investigate bulk structures and processes spanning multiple length scales from centimeters to tens of nanometers. Keywords: neutron imaging; neutron scattering; small angle scattering; dark-field imaging 1. Introduction The largest and maybe also broadest length scales that are probed with neutrons are the domains of small angle neutron scattering (SANS) and imaging.
    [Show full text]
  • Arxiv:1901.04741V2 [Hep-Th] 15 Feb 2019 2
    Quantum scale symmetry C. Wetterich [email protected] Universität Heidelberg, Institut für Theoretische Physik, Philosophenweg 16, D-69120 Heidelberg Quantum scale symmetry is the realization of scale invariance in a quantum field theory. No parameters with dimension of length or mass are present in the quantum effective action. Quantum scale symmetry is generated by quantum fluctuations via the presence of fixed points for running couplings. As for any global symmetry, the ground state or cosmological state may be scale invariant or not. Spontaneous breaking of scale symmetry leads to massive particles and predicts a massless Goldstone boson. A massless particle spectrum follows from scale symmetry of the effective action only if the ground state is scale symmetric. Approximate scale symmetry close to a fixed point leads to important predictions for observations in various areas of fundamental physics. We review consequences of scale symmetry for particle physics, quantum gravity and cosmology. For particle physics, scale symmetry is closely linked to the tiny ratio between the Fermi scale of weak interactions and the Planck scale for gravity. For quantum gravity, scale symmetry is associated to the ultraviolet fixed point which allows for a non-perturbatively renormalizable quantum field theory for all known interactions. The interplay between gravity and particle physics at this fixed point permits to predict couplings of the standard model or other “effective low energy models” for momenta below the Planck mass. In particular, quantum gravity determines the ratio of Higgs boson mass and top quark mass. In cosmology, approximate scale symmetry explains the almost scale-invariant primordial fluctuation spectrum which is at the origin of all structures in the universe.
    [Show full text]
  • Minimal Length Scale Scenarios for Quantum Gravity
    Living Rev. Relativity, 16, (2013), 2 LIVINGREVIEWS http://www.livingreviews.org/lrr-2013-2 doi:10.12942/lrr-2013-2 in relativity Minimal Length Scale Scenarios for Quantum Gravity Sabine Hossenfelder Nordita Roslagstullsbacken 23 106 91 Stockholm Sweden email: [email protected] Accepted: 11 October 2012 Published: 29 January 2013 Abstract We review the question of whether the fundamental laws of nature limit our ability to probe arbitrarily short distances. First, we examine what insights can be gained from thought experiments for probes of shortest distances, and summarize what can be learned from different approaches to a theory of quantum gravity. Then we discuss some models that have been developed to implement a minimal length scale in quantum mechanics and quantum field theory. These models have entered the literature as the generalized uncertainty principle or the modified dispersion relation, and have allowed the study of the effects of a minimal length scale in quantum mechanics, quantum electrodynamics, thermodynamics, black-hole physics and cosmology. Finally, we touch upon the question of ways to circumvent the manifestation of a minimal length scale in short-distance physics. Keywords: minimal length, quantum gravity, generalized uncertainty principle This review is licensed under a Creative Commons Attribution-Non-Commercial 3.0 Germany License. http://creativecommons.org/licenses/by-nc/3.0/de/ Imprint / Terms of Use Living Reviews in Relativity is a peer reviewed open access journal published by the Max Planck Institute for Gravitational Physics, Am M¨uhlenberg 1, 14476 Potsdam, Germany. ISSN 1433-8351. This review is licensed under a Creative Commons Attribution-Non-Commercial 3.0 Germany License: http://creativecommons.org/licenses/by-nc/3.0/de/.
    [Show full text]
  • Natural Length Scale from Cosmological Holographic Principle Matches Proton
    Natural Length Scale from Cosmological Holographic Principle Matches Proton Simon WW Manley [email protected] Abstract A natural unit of length, determined by applying the Holographic Principle to the Hubble sphere, matches the diameter of the proton, the smallest relevant size in nature. Unlike traditional Large Numbers coincidences, which are accurate only to order of magnitude, this agreement is precise. Introduction This brief Note discusses the natural length scale implied by the restriction on the information density of a region under the Holographic Principle. 3 1/2 -35 The Planck length, lP = (hG/2πc ) = 1.616×10 m, is 20 orders of magnitude smaller than the atomic nucleus. Mathematically, this is trivial, following from the weakness of gravity. But from an informational perspective, it seems deeply disturbing. If we naïvely consider the world to be about as rich in information as a discrete 3-dimensional lattice of spacing lP, reality appears to be severely over-specified. Since John Archibald Wheeler’s promotion of the epigrammatic “It from Bit” hypothesis [Wheeler, 1989], the physics community has become increasingly committed to the concept of information being the deep foundation underlying quantum mechanics [Zeilinger, 1999]. This visionary idea was recently given a rigorous mathematical formulation by Chiribella and colleagues [2011]. The relationship of information to geometry was first made explicit in black hole 2 thermodynamics, where each bit requires an area of 4 lP on the event horizon [Bekenstein, 1973]. The universality of this relationship, implying dimensional reduction in quantum gravity, was first proposed by ’t Hooft [1993], and through work of Thorn and Susskind, refined into a Holographic Principle [Susskind, 1994].
    [Show full text]
  • Arxiv:1411.4673V1 [Hep-Ph] 17 Nov 2014 E Unn Coupling Running QED Scru S Considerable and Challenge
    Attempts at a determination of the fine-structure constant from first principles: A brief historical overview U. D. Jentschura1, 2 and I. N´andori2 1Department of Physics, Missouri University of Science and Technology, Rolla, Missouri 65409-0640, USA 2MTA–DE Particle Physics Research Group, P.O.Box 51, H–4001 Debrecen, Hungary It has been a notably elusive task to find a remotely sensical ansatz for a calculation of Sommer- feld’s electrodynamic fine-structure constant αQED ≈ 1/137.036 based on first principles. However, this has not prevented a number of researchers to invest considerable effort into the problem, despite the formidable challenges, and a number of attempts have been recorded in the literature. Here, we review a possible approach based on the quantum electrodynamic (QED) β function, and on algebraic identities relating αQED to invariant properties of “internal” symmetry groups, as well as attempts to relate the strength of the electromagnetic interaction to the natural cutoff scale for other gauge theories. Conjectures based on both classical as well as quantum-field theoretical considerations are discussed. We point out apparent strengths and weaknesses of the most promi- nent attempts that were recorded in the literature. This includes possible connections to scaling properties of the Einstein–Maxwell Lagrangian which describes gravitational and electromagnetic interactions on curved space-times. Alternative approaches inspired by string theory are also dis- cussed. A conceivable variation of the fine-structure constant with time would suggest a connection of αQED to global structures of the Universe, which in turn are largely determined by gravitational interactions. PACS: 12.20.Ds (Quantum electrodynamics — specific calculations) ; 11.25.Tq (Gauge field theories) ; 11.15.Bt (General properties of perturbation theory) ; 04.60.Cf (Gravitational aspects of string theory) ; 06.20.Jr (Determination of fundamental constants) .
    [Show full text]
  • 1 Scale-Relativistic Estimate of the Fine Structure Constant
    1 Scale-Relativistic Estimate of the Fine Structure Constant Laurent Nottale CNRS, DAEC, Observatoire de Paris-Meudon, 92195 Meudon Cedex, France Abstract. The low energy value of the fine structure constant is theoretically estimated to within 1‰ of its observed value in the framework of the theory of scale relativity, in which the Planck length-scale is reinterpreted as a lowest, limiting, unpassable length, invariant under dilatations. This estimate is performed by using the renormalization group equations to evolve the QED coupling constant from infinite energy, where the bare mean electroweak coupling is assumed to reach its “natural” value 1/4π2, down to the electron energy. A consequence of this calculation is that the number of Higgs boson doublets is predicted to be NH = 1. Completed: 28 December 1992 Revised: 14 April 1993 2 1. Introduction Present high energy physics seems to be faced with several unsolved fundamental problems, among which: (i) the problem of divergences of self-energies and charges in QED; (ii) the nature of the Planck scale; (iii) the origin and values of universal scales, such as the Electroweak and GUT scales; (iv) the values of coupling constants. These problems are clearly related with one another. Indeed, consider in particular the question of the theoretical understanding of the coupling constant values which we address in the present letter. Once it was realized that vacuum polarization by virtual particle-antiparticle pairs resulted in a screening of bare charges, it became clear that the most straighforward programme for theoretically predicting the low energy value of the electromagnetic coupling (i.e., the fine structure constant) was to derive it from its “bare” (infinite energy) value and from its variation with scale.
    [Show full text]
  • Scale-Relativistic Corrections to the Muon Anomalous Magnetic Moment
    Scale-relativistic correction to the muon anomalous magnetic moment Laurent Nottale LUTH, Observatoire de Paris-Meudon, F-92195 Meudon, France [email protected] April 20, 2021 Abstract The anomalous magnetic moment of the muon is one of the most precisely mea- sured quantities in physics. Its experimental value exhibits a 4.2 σ discrepancy −11 δaµ = (251 ± 59) × 10 with its theoretical value calculated in the standard model framework, while they agree for the electron. The muon theoretical calculation involves a mass-dependent contribution which comes from two-loop vacuum po- larization insertions due to electron-positron pairs and depends on the electron to muon mass ratio x = me/mµ. In standard quantum mechanics, mass ratios and inverse Compton length ratios are identical. This is no longer the case in the spe- cial scale-relativity framework, in which the Planck length-scale is invariant under dilations. Using the renormalization group approach, we differentiate between the origin of ln x logarithmic contributions which depend on mass, and x linear con- tributions which we assume to actually depend on inverse Compton lengths. By defining the muon constant Cµ = ln(mP/mµ) in terms of the Planck mass mP, the − 2 3 C2 resulting scale-relativistic correction writes δaµ = α (x ln x)/(8 µ), where α is the fine structure constant. Its numerical value, (230 ± 16) × 10−11, is in excellent agreement with the observed theory-experiment difference. The Dirac equation predicts a muon magnetic moment, Mµ = gµ(e/2mµ)S, with gyromagnetic ratio gµ = 2. Quantum loop effects lead to a small calculable deviation, parameterized by the anomalous magnetic moment (AMM) aµ =(gµ − 2)/2 [1].
    [Show full text]
  • Arxiv:1610.02961V1 [Nucl-Th] 10 Oct 2016  Power Counting Scheme
    General aspects of effective field theories and few-body applications Hans-Werner Hammer and Sebastian König Abstract Effective field theory provides a powerful framework to exploit a separation of scales in physical systems. In these lectures, we discuss some general aspects of effective field theories and their application to few-body physics. In particular, we consider an effective field theory for non-relativistic particles with resonant short-range interactions where certain parts of the interaction need to be treated nonperturbatively. As an application, we discuss the so-called pionless effective field theory for low-energy nuclear physics. The extension to include long-range interactions mediated by photon and pion-exchange is also addressed. 1 Introduction: dimensional analysis and the separation of scales Effective field theory (EFT) provides a general approach to calculate low-energy observables by exploiting scale separation. The origin of the EFT approach can be traced to the devel- opment of the renormalization group [1] and the intuitive understanding of ultraviolet diver- gences in quantum field theory [2]. A concise formulation of the underlying principle was given by Weinberg [3]: If one starts from the most general Lagrangian consistent with the symmetries of the underlying theory, one will get the most general S-matrix consistent with these symmetries. As a rule, such a most general Lagrangian will contain infinitely many terms. Only together with a power counting scheme that orders these terms according to their importance at low energies one obtains a predictive paradigm for a low-energy theory. The Lagrangian and physical observables are typically expanded in powers of a low- momentum scale Mlo, which can be a typical external momentum or an internal infrared 1 scale, over a high-momentum scale Mhi Mlo.
    [Show full text]
  • PROTON RADIUS PUZZLE and LARGE EXTRA DIMENSIONS 1. Introduction the Charge Radius of the Proton Has Drawn a Lot of Theoretical
    PROTON RADIUS PUZZLE AND LARGE EXTRA DIMENSIONS LI-BANG WANG* Department of Physics, National Tsing Hua University, Hsinchu,30013,Taiwan [email protected] WEI-TOU NI Department of Physics, National Tsing Hua University, Hsinchu,30013,Taiwan [email protected] Received Day Month Day Revised Day Month Day We propose a theoretical scenario to solve the proton radius puzzle which recently arises from the muonic hydrogen experiment. In this framework, 4 + n dimensional theory is incorporated with modified gravity. The extra gravitational interaction between the proton and muon at very short range provides an energy shift which accounts for the discrepancy between spectroscopic results from muonic and electronic hydrogen experiments. Assuming the modified gravity is a small perturbation to the existing electromagnetic interaction, we find the puzzle can be solved with stringent constraint on the range of the new force. Our result not only provides a possible solution to the proton radius puzzle but also suggests a direction to test new physics at very small length scale. Keywords: proton size puzzle; large extra dimensions; Lamb shift; muonic hydrogen; atomic spectroscopy. PACS Nos.: 04.50.-h, 14.20.Dh, 31.30.jf, 31.30.jr, 42.62.Fi 1. Introduction The charge radius of the proton has drawn a lot of theoretical interest since a very precise Lamb shift measurement has been performed on muonic hydrogen.1 The measured rms charge radius rp = 0.8418(7) fm is significantly smaller than the CODATA value of 0.8775(39) fm, which is a combined result
    [Show full text]
  • Ext-2004-043.Pdf
    The Charge-Mass-Spin Relation of Clifford Polyparticles, Kerr-Newman Black Holes and the Fine Structure Constant Carlos Castro Center for Theoretical Studies of Physical Systems Clark Atlanta University, Atlanta, GA. 30314 A Clifford-algebraic interpretation is proposed of the charge, mass, spin relationship found recently by Cooperstock and Faraoini which was based on the Kerr-Newman metric solutions of the Einstein-Maxwell equations. The components of the polymomentum associated with a Clifford polyparticle in four dimensions provide for such a charge, mass, spin relationship without the problems encountered in Kaluza-Klein com- pactifications which furnish an unphysically large value for the electron charge. A physical reasoning behind such charge, mass, spin relationship is provided, followed by a discussion on the geometrical derivation of the fine structure constant by Wyler, Smith, Gonzalez-Martin and Smilga. To finalize, the renormalization of electric charge is discussed and some remarks are made pertaining the modifications of the charge-scale relationship, when the spin of the polyparticle changes with scale, that may cast some light into the alleged Astrophysical variations of the fine structure constant. EXT-2004-043 01/09/2003 Key words : Clifford Algebras; Black Holes; Dirac electron. PACS : 11 E88, 15 A66, 83 C57 1. INTRODUCTION 1.1 CLIFFORD ALGEBRAS IN PHYSICS Clifford algebras display a rich mathematical structure which is very useful for a unified description of geometry and physics [1,2,3,4,5,6,9]. For example, a geometric approach to the physics of the Standard Model in terms of Clifford algebras was advanced by [3] . Important applications have also been found in string theory, extended objects, gravity, QFT...
    [Show full text]