PoS(STORI11)020 . − http://pos.sissa.it/ Ξ hypernuclei, give ΛΛ hyperons in the storage ring HESR − ’s are indicated. Ξ − Ξ ∗ is the basic tool to produce all systems containing double . These − Ξ [email protected] [email protected] [email protected] [email protected] Speaker. information about their .scarce at In present, spite due of to theThe the great techniques difficulty exploited interest up in of to producing now these to andtoghether topics, produce stopping with doubly data the the strange are systems related short are physics living here items.tiprotons shortly reviewed, Then for the the proposal hyperon of production PANDAtargets Collaboration and is to the briefly use design described. an- of Finallyinserted the the in innovative problems the system arising ring of and from two the thehigh antiproton separated rates interacion beam of of stopped are the illustrated solid and target, the possible solutions for getting The systems allow to investigate the hyperon-nucleon andover hyperon-hyperon the . non More- mesonic decays, in particular the hyperon induced decay of ∗ Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. c

8th International Conference on Nuclear PhysicsOctober at 9-14, Storage 2011 Rings-Stori11, Laboratori Nazionali di Frascati dell’INFN, Italy Andrea Lavagno Politecnico di Torino and INFN-Torino E-mail: Hannan Younis Politecnico di Torino and INFN-Torino E-mail: Riccardo Introzzi Politecnico di Torino and INFN-Torino E-mail: in PANDA Felice Iazzi Politecnico di Torino and INFN-Torino E-mail: Production of PoS(STORI11)020 ] − 1 Ξ hyperon − Felice Iazzi beam, as it Ξ − ’s bound in a hyperons and Λ K − Ξ hyperon (strangeness ’s and devising suit- Λ − Ξ hyperon from both − Ξ exotic atoms, which contain a − Ξ 2 hypernuclei, in which the hyperon is absorbed inside a − Ξ hyperonic atoms. They are formed by capture of the hadron nearly ’s in a totally different way with respect to the use of − − Ξ Ω ], the former being ready to take data and the latter to operate in nearly 5 2 and − Ξ hyperons at HESR , − − with nucleons in the single hypernuclei. Some data from the hyper-atoms containing Σ Ξ exotic atoms belong to the class of the hadronic atoms, which includes pionic, kaonic, Λ − EXOTIC ATOMS Ξ − Ξ Concerning the production of strange baryons it must be remarked that the The project of the antiproton ring HESR at FAIR suggested PANDA Collaboration to exploit In Section 2 the main features of the physics related to the S=-2 systems and the status of art of The systems containing double strangeness are: I) the I) The Nevertheless the physics items related to the electromagnetic, weak and strong interactions of Up to now the starting point of nearly all experiments has been the creation of the The most recent developments in the field of the Strong Interaction Physics lead the High hyperon (S=-1, I= 1) are available while the status of art of the investigations of the systems − antiprotonic, and antiprotons (FAIR)[ able setups to optimize their absorption in atoms and nuclei. this antibaryon to produce has been done in the pastthe and ring foreseen and this for leads JPARC. to This asetup, technique number requires strongly of to constraints dominated insert due by a to the a) targetwhich the inside short impinges beam lifetime lifetime, on of b) the the the geometrystated detectors. hyperon, of that the c) the Work the performances is of overwhelming in HESR background can progress fit to the needs solve of these thethe problems data DSS is experiment. and briefly it reviewed; in isand Section antiprotons already 3 are the discussed; reactions the which project produce ofDSS the in experimental PANDA setup is for illustrated producing in Section 4 and the conclusions are drawn in2. Section 5. Doubly Strange Systems: physics and status of art nucleus. The main features of theirin interactions the and following. the status of art of the available data are listed years. Σ containing S=-2 (the so called Doubly Strange Systems, DSS) are basically atthe DSS an are early of stage. great interest, asamount discussed of in such the systems next chapter are and welcome. new techniques to produce a large nucleus; III) the double hypernuclei whose strangeness contents is due to a pair of Production of 1. Introduction Energy Community to investigate very rare reactions, e.g.formation of the heavy production quark of systems. strange baryons To fullfil andprojectiles the the goal are of requested. getting a Two rich hadronic statistics, machines intense will beams of supply the intense beams of kaons (JPARC)[ S=-1, I=0) has beenteraction widely of investigated and a lot is known about the strong and weak in- (S=-2, I=1/2), whose strangeness contents issorption transferred of to the a system hyperon. (atomlooking Therefore or for nucleus) the intense through goal beams ab- of of getting particles high which can statistics produce for large DSS amount has of to be achieved hyperons in an atomic orbit; II) the PoS(STORI11)020 (2.1) (2.2) to be − stopping Σ Felice Iazzi interaction − Ξ N of 50 [MeV/c], − − Λ 20 and 25 [ps] in K , ], in the OBE mechanism hyperon, whose production hyperatom, which has been 6 − − hyperon has the heaviest mass Σ Ω − Ξ . After capture they cascade emitting n 0 ..., I=1/2) can be exchanged, while all 0 / / K + + π K momenta. Tipically, for are absent in the panorama of the hyperatom + + − − − − K Ω Σ Ξ 3 = = and N N − + + Ξ 217 [MeV/c] and goes to stop in 60 − − hyperon inside the nucleus. As said above, it is formed after K K ≈ 127 and 133 [ps] respectively, greater or comparable with the − , ] that Ξ 3 with forward momentum greater than 500 [MeV/c]. The coupling no strange meson ( − Ξ N Ξ → ] that in an atom the absorption level increases monotonically with the hadron 5 N , hyperons at HESR Ξ 4 − , hyperon has a good probability to be captured into an atom. On the other hand the Ξ 3 HYPERNUCLEI − hypernucleus contains a Σ − − Ξ Ξ It has been alredy remarked [ By measuring shift and width of the levels, the nuclear potential can be determined in the II) A The strong interaction presents some peculiar aspects different from the The total mass in the final state of eq.2.1 is less than in the initial state. This allows absorption from an atomic level. Inside the nucleus the hyperon interacts with the nucleons exits in the forward direction at 05 [GeV/c], producing − − . to describe the is still very difficult fromamong the the hadronic experimental atoms point and of the absorption view, levels the should be the highest ones. observed. The reason of thisnow to lack produce can these be hyperons: found in the specific features of the reactions used until mass and, for the same hadron, with the atomic number. Apart the data even if their mass and lifetime are quite close to those ones of Production of at rest into an atomicAuger orbit, electrons in or general X in rays. a Whenthe level the low with lowest density levels high region are reached, ofstrong the the interaction hadron between nuclear wave hadron function matter. and nucleus, overlaps which Theof adds lowest to the the levels Coulomb X-rays are potential. emitted shifted The detection hadron and during broadened the reaches by transitions a the allows broadened toabsorption level level: measure the these therefore absorption shift the into andshift first and the brodened width. width nucleus of level the is When is absorption the the level fastdifferent can last masses be and measured of and the in different the each levels level exotic atomic in atom.therefore is cascade which they Different called and hadrons end the have the only Coulomb cascade and the at strongpointed different potential out absorption start [ levels to in interplay: different atoms. It has been already produced with a low momentumΣ using very low carbon, lead and iron respectively. Allproduced these time intervals are quite lessfinal than state of the eq.2.2 lifetime has and a each mass1 greater than the initial one andtimes the threshold in of the the above reaction materials is are around lifetime: 332 the probability to be captured into an atom is stronglyperipheral reduced. region of theand nucleus nuclear where forces the overlap. nuclear Datadensity density from nuclear varies potential. different atoms appreciably are and needed the to Coulomb completely describe the low Ξ undergoing both strong interaction and weak decay. acting in the single hypernuclei. In fact, as remarked by Motoba [ PoS(STORI11)020 Σ Λ 366

and ≈

15 A N Λ , Σ BE vs A of Felice Iazzi 5 [GeV/c]. p . ∆ of the Double ) . Other creation

Z , with hyperons inside a Λ 10 N A ΛΛ + Λ ( + Λ − ΛΛ ], which look increasing Σ B 9 → can interact also with the , momentum of 0 p 16 [MeV] respectively. An 8

→ 5 Λ , − + ≈ N 7 Ξ 24 [mb] and the cross section − − + Ξ Ξ ≈ − V hypernuclei; b) B.E. and ] for ) Ξ − p 11 Ξ −

0 Ξ

5 0 5

hypernuclei, doesn’t affect the possibility -

25 20 15 10

LL LL ] MeV ] MeV .[ B.E [ B D → Λ p can be exchanged. On the other hand, in the − ) .. b) Ξ 4 ( ρ , σ π

, 469 [MeV/c] and

30 -nucleus potential. Each η A ≈ to the nucleus, as occurs in a single hypernucleus, with , Λ is related to the binding energy n , ω

Λ Λ 25 p ΛΛ 1 ( hypernuclei presents some different mechanisms with respect V = −

I Ξ 20 ] succeeded in calculating an attractive potential well for carbon , with 10 , also called Double Hypernucleus, contains 2 n

Z 0 or + 15 related to the 14 [MeV] and for scintillating fibers A ΛΛ 24 [MeV]. Experiments E885 at AGS and E224 at KEK found smaller Λ = ) hypernuclei data at present is very poor. Some binding energies have been I

Z ≈ − → A Λ 10 − − ( p Ξ 21 Ξ Λ nucleons, which are created by the reaction V B 5 [mb] have been measured by Ahn et al. [ +

≈ A 5 hyperons at HESR − hypernuclei ≈ − Ξ − Ξ ) Ξ V HYPERNUCLEI

ΛΛ 0 hypernucleus coupling only strange mesons can be exchanged.

ΛΛ 5 0 5 a): Binding Energy vs mass number A of the observed - 10 25 20 15

hypernuclei. First, the Pauli principle, which is responsible for the strong decrease of the

ΛΛ and the interaction energy

→ B.E. [ B.E. ] MeV ΛΛ ΛΛ Λ p Λ A III) Also the weak decay of the The strong interaction binds each The amount of − → Ξ a) ( ’s interact strongly with the nucleons and can decay weakly in both mesonic and non mesonic N in the range values for carbon, with increasing mass number (seelarge Figure errors, 1.a). Dover and Even Gal though [ these measurements are affected by upper limit of theσ total elastic cross section Figure 1: non-strange mesons of to the branching ratio of non mesonic weak decay in heavy Production of the observed Ξ of the decays: mechanisms have been studied, which will beΛ discussed in the next section. Insidemode. the The nucleus mesonic both mode undergoes thehypernucleus. same Both constraints strong due to and the weak Pauli interactions principle present as peculiar the features. single a binding energy other [MeV/c]. In fact the momentafrom of the the nucleus final and statesdifferent in hyperons from are case those large of enough of sticking to thecould after allow shed nucleons. them rescattering light on to Moreover they the exit the have role branching of a the ratios set isospin. of of the quantum decaysmeasured numbers in into old experiments with bubble chambers and emulsions [ nucleus made of PoS(STORI11)020 , ΛΛ B (3.1) (2.5) (2.3) (2.4) ∆ show an Felice Iazzi interaction ΛΛ B ΛΛ ]. Nevertheless ] in an emulsion 16 12 , 15 ] weak interaction. For ] , c c / / − 14 ) ΛΛ Ξ and on the fragmentation of Z + MeV A Λ MeV [ Λ [ 0 ( Λ K ...). . B 321 ω 2 433 , interaction energy can be obtained. ΛΛ → < − B η < n ) p ∆ n / Z / ΛΛ + Σ Λ p − p A ΛΛ ( K < < ΛΛ B 5 ≡ ) 0, neglecting ; ], a recent contribution came from KEK-E373 exper- Z − ≈ 13 ; 280 Ξ A ΛΛ ; 404 of the single hypernuclei. The hyperons and nucleons are Λ ( p n p + hypernucleus is the only system which allows to study the B + ΛΛ Γ + + / B − Λ K n ΛΛ ∆ Σ Γ + hypernuclei has several possible final states, depending on the + ≡ → Z Z A p ΛΛ ΛΛ A V + → → − − Z 11 [MeV] and Z K hyperons and Doubly Strange Systems A ΛΛ ≈ A ΛΛ − Λ Ξ interaction. B hyperons at HESR ΛΛ − Ξ 5, for = Z , Kaons of 1.66 and 1.8 [GeV/c] were used and the targets were nuclei: reactions 3.1 could be All experiments dedicated to DSS (KEK, BNL-AGS, JPARC) planned to use beams in are unique for double hypernuclei and could shed light on the No data about this decay are available at present. Concerning the OBE mechanism it must be recalled that the contribution to the By measuring the binding energy of the Double Hypernucleus, if the binding energies of the The set of available data is today scarce: after the discovery in the 60’s [ The weak decay of the 11 interaction, because all the other techniques, like hyperon-hyperon scattering measurements, = considered quasi free inside the nucleus due to the high beam momentum. Two types of reactions instance it could be very interesting2.5 to present test problems whether like the the relative ratio branchingemitted ratios with of quite the high eqs. momenta 2.4 andin and should eqs. be 2.4 easily detectable. and 2.5 TheA are momentum calculated ranges under reported the hypothesis of recoiless, nearly at rest, residual nucleus the reactions: 3. Production of Measurements of several hypernuclei arethe needed core in of order the to obtain a satisfying knowledge about comes only from the non-strange mesons with zero isospin ( iment, which used a diamond target, scintillating fibers and emulsion [ the hypernucleus after formation. In particular the so called Hyperon Induced Weak Decays: 2 single hypernuclei involved in eq.2.3 are known, the various combinations of mesonic and non mesonic decay of each are at present impossible. Production of Hypernucleus by: experiment and a result from KEK-E176 [ the total collection includes less thanincreasing ten trend double for hypernuclei. increasing Their binding masswhich energies are number expected A to decrease (see for Figure largeconstant nuclei 1.b); with corresponding their to A. large separation Anyway average distances, nothing energies lookpoor. is quite It definite must because be the remarked errorsΛΛ that are the large and the statistics is very PoS(STORI11)020 ], 18 (3.4) (3.5) Felice Iazzi ] that a fraction ’s is foreseen to − 20 hypernucleus [ Ξ ’s is independent upon production threshold), ; (3.2) ; (3.3) ΛΛ − ) ) π 1 ] 2 Ξ sr − − − / Z Z Ξ ( ( nb − [ + A Ξ A ΛΛ 0 10 hyperon exits from the hit nucleus Ξ ] and of the + + < − + + 17 → Ξ ΛΛ K K n C target surrounding the pipe. With this Ω + 12 d → p → / hypernucleus after interaction with a . -hyperatom during their formation process. σ ] d )] − − 1 ΛΛ Ξ 6 Ξ ) ; − ] + Z ; ¯ hypernucleus [ sr K ( 6 [GeV/c]. As for kaon beams, reactions 3.5 could be − / ’s of 3.0 [GeV/c] (below the , . − A Λ p 2 Ξ − Ξ nb + [ K + ≈ 0 ( ) go to stop in a ¯ 89 p p + π [ [ − p hyperon exits from the nucleus and goes to stop losing energy Ξ ≈ Ξ ]. A target dedicated to the production of − → → − Ξ → 19 Ξ . In an indirect reaction the Z p Z Ω A A − d + / K ¯ p + + σ d − − K K such events. ’s (per produced 4 hyperons at HESR − ’s are accumulated in the Collector Ring (CR) and then injected, as a bunch of initial Ξ − p Ξ 3 − , into the High Energy Storage Ring (HESR). A target located inside the beam pipe is 0 I hypernucleus, which d) transforms into a These very low values are due to the low probability of a 2-step process inside the same PANDA Collaboration designed a specific assembly of detectors to be arranged all around In the indirect reactions the whose momentum threshold is At FAIR ¯ In both cases an intermediate state preceeds the formation of DSS, suggesting low probabilities The availability of intense fluxes of antiprotons at the FAIR project suggested to produce DSS can decay in each step, mostly during the slowing down. Maximizing the number of stopped − ’s in a target is the aim of all dedicated experiments: E07 experiment at JPARC is expected to Ξ − − a thin target and a suitable geometry of the beam pipe, it has been calculated [ nucleus. The direct reactions don’t produce any considered quasi free inside the nucleus. the antiproton beam of HESR [ be inserted inside the beam pipe. Using ¯ gave a low value and an upper limit (after no observations) respectively: of some 10 configuration the choice of the internal targetthe for design maximizing of the stopped the external target,In allowing this different way nuclei both to requirements besatisfied. of explored with the the DSS same physics, efficiency. high statistics and several hypernuclei, can4. be The internal target of PANDA inside HESR contents Production of can occur inside the nucleus:in direct the and same indirect nucleus reactions. hitand In by is a captured direct by reaction an the other DSS nucleus. is Direct formed reactions are: by ionization in the surroundingatom, matter. b) Then makes a) transitions is down to captureda the in lowest an levels atomic and orbit c) is forming absorbed an inside hyper- the nucleus forming Ξ Ξ produce some 10 starting from the basic reactions: for both mechanisms. In factforward two differential experiments cross at section BNL-AGS, dedicated of to the the measurement of the PoS(STORI11)020 3 is th f ≈ − (4.2) (4.1) / s c n but the n ¯ p ≡ Felice Iazzi 7 d t 10 · and p t up to 6 ’s and the background [annihilation/s]. Since − 0 6 ] I Ξ 3 [s]. Taking into account , and to the total hadronic 10 of revolutions the survived SCS · w decreases after each ≈ σ c 5 potentials and the interplay of n · n I of the target material by: 2 by steering the beam during the ≈ Z , CR accumulates a new bunch at B ΛΛ r d SCS t + , width σ s T + and σ p · t N 3 / ≡ 2 − T τ A · t − n [ f · Ξ and form doubly strange systems. A system of − ] e , thickness B . After a number − · r n ρ I 7 · Ξ 0 ’s becomes of few thousands per day. In order to I is the beam lifetime. The − w · τ Ξ = s n · , efforts have to be done in order to increase as much as I − Av Ξ per day. N A · 4 ρ = [ ] . During the interval 1 ] the annihilation constraint is satisfied for production and for hypernucleus formation, has been designed, with − 21 m ) − τ µ · Ξ f are mass number, charge and overlapping fraction of beam and target, it is ( is long, the bunch contents is big and the background initially makes blind B 100 [ T r t ≈ and Single Coulomb Scattering cross section w hyperons at HESR and T /s. If − Z ¯ is the revolution frequency and σ p Ξ , f 7 A 15 [s], the average rate of stopped > p PANDA Collaboration proposed to profite of the intense fluxes of antiprotons at HESR, in the The doubly strange systems open wide perspectives to study the role played by the strangeness where where t ] and width ’s at a rate of the order of some 10 m − µ one target to be inserted insidemaximize the the beam hyperon pipe rate and under interacting some withthe constraints the detectors. due beam. to The This the required setup beam features requires lifetime to of and the the background target on and performances of the beam have been singled possible the production of this hyperon. FAIR complex, to produce high rates oftwo stopped separated targets, for cycle is under study, in ordersolution, likely to feasible overlap at the HESR, target could withΞ make the nearly less negligible dense the ratio part and of allow the a beam production spot. of This 5. Conclusion in the strong and weak interactions.the In particular Coulomb the and nuclear potentialthe in rich the variety of periphery mesonic of and non thedouble mesonic nucleus (in hypernuclei can particular could the be help hyperon investigated. induced) in decaythis Moreover understanding modes goal of the the high hyperon-hyperon statistics weak is interaction.these required systems To are and fullfil formed the starting data from should be spread along the periodic table. Since convenient to choose light, thin, wire-shaped targets. Choosing a carbon wire of thickness [ beam lifetime at 3 [GeV/c] is verythat small and the bunch is consumedincrease in this rate, the technique of decreasing strongly the factor bunch is small and acooling, new accelerating injection (decelerating), is steering required. and Afterin squeezing each the the injection bunch beam before a pipe: the time this targetthe must time time is be (constant for inserted spent in data for acquisition all pre- [ cycles) is called ‘preparation time’ produced in each revolution are proportional to a rate of 10 some detectors. The maximum tolerable background in PANDA is Production of illuminated at the beginningrevolution by as: the full bunch, then the contents the beam lifetime is related to the target density cross section PoS(STORI11)020 , 633 - , − Phys. , 691 Ξ (2007) 209 reaction on Felice Iazzi ) + (2001) 212502 ’s per day can 789 K − Hyperfine , Acta Phys. Pol. B , Ξ 87 (1979) 333 − Phys. Lett. B , Hyperfine Interact. K , (1997) 385 , ( 54 , EPJ Web of (2001) 132504 Nucl. Phys. A (1963) 29 287 (2010) 207 , 87 stopped 11 meson interactions with (2009) 191-232, and Nucl.Phys. A 4 835 − , Hypernuclei via the (1959) 397 828 Λ Phys. Rev.Lett. 3 atoms at J-PARC , Nuovo Cim. A Phys. Rep. − , , Ξ -hyperonic atoms of W and Pb Double- Σ Phys. Rev.Lett. Phys. Rev.Lett. , Nucl.Phys. A , (1983) 309 , Nucl.Phys. A , Phys.Rev.Lett. 146 , -atom spectroscopy at PANDA − 8 Ξ hyperons − hypernuclei and the H dibarion in the Ann. Phys. Ξ He Double Hypernucleus Λ , -p scattering cross sections at low energy − 6 ΛΛ Ξ He Double Hypernuclei (1968) 174 Recents results from E885: search for doubly strange objects (2006) 289 4 ΛΛ 26 561 hypernuclei Perspectives of the − Ξ (2000) 401 Double Hyperfragment Event Search for double- Production of double hypernuclei with antiprotons at PANDA Roadmap for double hypernuclei spectroscopy at PANDA Observation of a The identification of a cascade hypernucleus Double emission of hyperfragments in high energy K 478 Strong interaction effect measurements in (2001) 226c Beam Performance and Luminosity Limitation in the High-Energy Storage Ring Observation of a Double Hyperfragment Phys. Lett. B production in antiproton-nucleus collisions at 3 GeV/c Strong interaction physics from hadronic atoms − Toward more exoticness X-ray spectroscopy of , Measurement of the Production of a Ξ Nuclear capture at rest of 691 (2009) 81 hyperons at HESR Production and decays of S=-2 hypernuclei with hyperon mixing − (1993) 1263 193 Nucl. Instr. Meth. A Ξ , 47 Phys. Lett. B (2009) 89 , , (2010) 285 C (HESR) (2001) 213c-219c 193 Rev. C emulsion nuclei Hyperon Capture at Rest Reaction in a Hybrid Emulsion (2006) 214 references quoted therein Nucl.Phys. A 12 Conference 3,07008 (2010) Interact. 41 [1] K. Tanida et al, [2] K. Szymanska et al., [7] D.H. Wilkinson et al., [8] A.S. Mondal et al., [9] A. Bechdolf et al., [3] F. Iazzi and K. Szymanska, [4] C.J. Batty et al., [6] T. Motoba, [5] R.J. Powers et al., [21] A. Lehrach et al., [20] F. Ferro et al., be expected. References Production of out: a solution of the problem has been identified and rates of several 10 [10] C.B. Dover and A. Gal, [16] K. Nakazawa for KEK-E373 and J-PARC E07 collaborators, [11] J.K. Ahn et al., [12] M. Danysz et al., [13] S. Aoki et al., [14] H. Takahashi et al., [15] J.K. Ahn et al., [17] M. May and E885 Collaboration, [19] J. Pochodzalla et al., [18] K. Yamamoto et al.,