Double Anti-kaon Production in Nuclei by Stopped Anti-proton Annihilation

1. Double Anti-kaon Productionin Nuclei by Stopped Anti-proton Annihilation F.Sakuma, RIKEN International Workshop on ”Physics and Upgrade of the J-PARC Hadron Facility” (post Hyp-X workshop), Sep. 18-19, 2009

2. This talk is based on the LoIsubmitted in June, 2009.

3. Contents of this talk • Introduction of • “Kaonic Nuclear Cluster” • Possibility of • “Double-Kaonic Nuclear Cluster” • by Stopped-pbar Annihilation • Experimental Approach • Summary and Outlook

4. Introduction of “Kaonic Nuclear Cluster”

5. The Origin of Mass KEK-PS W.Weise NPA553, 59 (1993). J-PARC? SPS, RHIC, LHC QGP most of the mass of matter are given by neutron star Chiral Symmetry Breaking Mu,d~300MeV Higgs Mechanism Mu,d~3MeV the missing piece is exploring hadron properties in dense matter Mass-less Quark Mu,d=0MeV

6. Neutron Star the highest density matter in our familiar material is a nucleus high-density matter above the nuclear density? r0=0.17fm-3 =2.8x1017kgm-3 p core material of neutron stars Outer Crust Inner Crust  0.3-0.5r0 Outer Core  0.5-2r0 Inner Core  2-15r0 n --- the structure of neutron stars --- ~10-14m possibility of the existence of a kaon condensed phase

7. KN interaction The possibility of kaon condensation is supported by … theoretical investigations various models predict kaon condensation (mean field theories, effective interaction theories, …) experimental results Kaonic atom data indicates a strongly attractive KN interaction (KpX@KEK, DEAR@DAFNE) this suggests “the existence of deeply-bound K−-nuclei states” Y.Akaishi & T.Yamazaki, PLB535, 70 (2002).

8. Kaonic Nuclear Cluster (KNC) if deeply-bound kaonic nuclear states exist … the density of kaonic nuclei is predicted to be extreme high density T.Yamazaki, A.Dote, Y.Akiaishi, PLB587, 167 (2004). we will open new door to the condensed matter physics, like the inside of neutron stars

9. Theoretical Situation of KNC theoretical predictions for kaonic nuclei, e.g., K-pp • whether the binding energy • is deep or shallow • how broad is the width ? Koike, Harada PLB652, 262 (2007). DWIA 3He(K-,n)

10. Experimental Situation of KNC E549@KEK-PS E548@KEK-PS 4He（stopped K-,p) 12C(K-,n) K-pnn? E549@KEK-PS 12C(K-,p) 4He（stopped K-,LN) unknown strength between Q.F. & 2N abs. Prog.Theor.Phys.118:181-186,2007. missing mass - deep K-nucleus potential of ~200MeV PLB 659:107,2008 no “narrow” structure K-pp/ K-pnn? K-pn/ K-ppn? arXiv:0711.4943

11. Experimental Situation of KNC (Cont’d) peak structure  signature of kaonic nuclei ? K-pp? K-pp? K-pp? FINUDA@DAFNE OBELIX@CERN-LEAR DISTO@SATUREN NP, A789, 222 (2007) PRL, 94, 212303 (2005) arXiv:0810.5182 the situation is still controversial, because of no conclusive evidenceyet! We need conclusive evidence with observation of formationanddecay ! L-p invariant mass

12. Formation Decay Experimental Principle of J-PARC E15 • search for K-pp bound state using 3He(K-,n) reaction neutron 3He K-pp cluster K- Missing mass Spectroscopyvia neutron Mode to decay charged particles p L exclusive measurement byMissing mass spectroscopy and Invariant mass reconstruction p- Invariant mass reconstruction p

13. J-PARC E15 Setup Sweeping Magnet Beam Line Spectrometer Beam trajectory K1.8BR Beam Line CDS & target E15 will provide the conclusive evidence of K-pp neutron Neutron ToF Wall Beam Sweeping Magnet Neutron Counter flight length = 15m p n Cylindrical Detector System p- p 1GeV/c K- beam

14. What will happen to put one more kaon in the kaonic nuclear cluster? Possibility of “Double-Kaonic Nuclear Cluster” by Stopped-pbar Annihilation

15. Double-Kaonic Nuclear Cluster • The double-kaonic nuclear clusters have been predicted theoretically. • The double-kaonic clusters have much stronger binding energy and a much higher density than single ones. PL,B587,167 (2004). & NP, A754, 391c (2005). • How to produce the double-kaonic nuclear cluster? • heavy ion collision • (K-,K+) reaction • pbarA annihilation We use pbarA annihilation

16. Double-Strangeness Production with pbar The elementary pbar-p annihilation reaction: -98MeV is forbidden for stopped pbar, because of a negative Q-value of 98MeV However, if multi kaonic nuclear exists with deep bound energy, following pbar annihilation reactions will be possible! theoretical prediction B.E.=117MeV G=35MeV B.E.=221MeV G=37MeV

17. Double-Strangeness Production Yieldby Stopped-pbar Annihilation From several stopped-pbar experiments, the inclusive production yields are: Naively, the double-strangeness production yield would be considered as: g : reduction factor ~ 10-2

18. Past Experiments of Double-Strangeness Production in Stopped-pbar Annihilation Observations of the double-strangeness production in stopped pbar annihilation have been reported by only 2 groups, DIANA@ITEP and OBELIX@CERN/LEAR. Although observed statistics are very small, their results have indicated a high yield of ~10-4

19. Past Experiments (Cont’d) • DIANA[Phys.Lett., B464, 323 (1999).] • pbarXe annihilation • p=<1GeV/c pbar-beam @ ITEP 10GeV-PS • 700-liter Xenon bubble chamber, w/o B-field • 106 pictures7.8x105pbarXe inelastic  2.8x105pbarXe @ 0-0.4GeV/c

20. Past Experiments (Cont’d) • OBELIX(’86~’96) [Nucl. Phys., A797, 109 (2007).] • pbar4He annihilation • stopped pbar @ CERN/LEAR • gas target (4He@NTP, H2@3atm) • cylindrical spectrometer w/ B-field • spiral projection chamber, • scintillator barrels, jet-drift chambers • 2.4x105/4.7x104 events of 4/5-prong in 4He • pmin = 100/150/300MeV/c for p/K/p they discuss the possibility of formation and decay of K-K-nn and K-K-pnn bound system

21. Interpretation of the Experimental Results • Although observed statistics are very small, the results have indicated a high yield of ~10-4, which is naively estimated to be ~10-5. • Possible candidates of the double-strangeness production mechanism are: • rescattering cascades, • exotic B>0 annihilation (multi-nucleon annihilation) • formation of a cold QGP, deeply-bound kaonic nuclei, • H-particle, and so on the mechanism is NOT known well because of low statistics of the experimental results! single-nucleon annihilation rescattering cascades multi-nucleon annihilation B=0 B>0 B>0

22. Anyway, the double-strangeness production yield of ~10-4 makes it possible to explore the exotic systems, if exist. Experimental Approach

23. How to Measure? In the following discussion, we limit the reaction: (although K-K-pp decay modes are not known,) we assume the most energetic favored decay mode: final state = K+K0LL • We can measure the K-K-pp signal exclusively by detection of: • all particles, K+K0LL, using K0p+p- mode • 3 particles, and the other one is identified by missing mass We need wide-acceptance detectors.

24. K+K0LL Final State & Background This exclusive channel study is equivalent to the unbound (excited) H-dibaryon search! Possible background channels • direct K+K0LL production channels, like: be distinguished by inv.-mass only  major background source • S0gL contaminations, like: be eliminated by the kinematical constraint

25. Expected Kinematics • assumptions: • widths of K-K-pp/H = 0 • many-body decay =isotropic decay K+K0X momentum spectra B.E=109MeV B.E=150MeV B.E=200MeV (threshold) In the K-K-pp production channel, the kaons have very small momentum of up to 300MeV/c, even if B.E.=200MeV. We have to construct low mass material detectors.

26. Expected Kinematics (Cont’d) MH= 2ML LL spectra L-L opening-angle L momentum LL inv. mass strong correlation of LL opening-angle in K-K-pp/H productions

27. Beam-Line We would like to perform the proposed experiment at K1.1 or K1.8BR beam line pbar stopping-rate evaluation by GEANT4 • Incident Beam • momentum bite : +/-2.5% (flat) • incident beam distribution : ideal • Detectors • Carbon Degrader : 1.99*g/cm3 • Plastic Scintillator : l=1cm, 1.032*g/cm3 • Liquid He3 target : f7cm, l=12cm, 0.080*g/cm3 1.3x103 stopped pbar/spill @ 0.65GeV/c, ldegrader~14cm • 30GeV-9mA, • 6.0degrees • Ni-target pbarproduction yield with a Sanford-Wang pbar stopping-rate

28. Expected Double-Strangeness Yield • pbar beam momentum : 0.65GeV/c • beam intensity : 3.4x104/spill/3.5s • pbar stopping rate : 3.9% • stopped-pbar yield : 1.3x103/spill/3.5s • Double-strangeness production : 1x10-4/stopped-pbar  9.6x104 double-strangeness/month a mere assumption! • branching ratio to K+K0LL final state : 0.1  9.6x103 K+K0LL/month

29. Detector Design • design concept • low material detector system • wide acceptance with pID • useful for other experiments We are considering 2-types of detector E15 setup @ K1.8BR • B = 0.5T • CDC resolution : srf = 0.2mm • sz’s depend on the tilt angles (~3mm) • ZTPC resolution : sz = 1mm • srf is not used for present setup

30. Detector Design (Cont’d) new dipole setup @ K1.1 • The design goal is to become the common setup for the f-nuclei experiment with in-flight pbar-beam • B = 0.5T • Double Cylindrical-Drift-Chamber setup • pID is performed with dE/dx measurement by the INC • INC resolution : srf = 0.2mm , sz = 2mm (UV) • CDC resolution : srf = 0.2mm, sz = 2mm (UV) • CDC is NOT used for the stopped-pbar experiment

31. Trigger Scheme expected stopped-pbar yield = 1.3x103/spill All events with a scintillator hit can be accumulated pbar3He charged particle multiplicity at rest CERN LEAR, streamer chamber exp. NPA518,683 91990).

32. Expected Signals • pbar+3HeK+K0S+ X (X=KKpp/H/LL) events are generated isotropically at the center of the detector system • # of generated events is 200k for each case • obtained yields are scaled by the estimated K+K0LL yield • chamber resolution, multiple scattering and energy losses are fully took into account using GEANT4 toolkit • charged particles are traced with spiral fit • assumptions: • widths of K-K0pp/H = 0 • B.E. of K-K-pp = 200MeV • MH = 2xML • branching ratio to K+K0LL final state = 0.1 • DAQ & analysis efficiency = 0.7  6.7x103 K+K0LL/month • Generated ratio  K-K-pp:H:LL = 0.1:0.1:0.8 • KKppLL and HLL decay branches are assumed to be 100% • S0gL contribution is NOT considered for the inclusive measurements LL invariant mass with (K+ or K0) reconstruction K+K0 missing mass with one more L reconstruction

33. Expected Signals (Cont’d) LL inv-mass with NEW setup LL inv-mass with E15 setup 25 K-K-pp events/month 24 K-K-pp events/month sK-K-pp = 27MeV sH = 0.7MeV sK-K-pp = 34MeV sH = 14MeV K+K0 miss-mass with NEW setup K+K0 miss-mass with E15 setup 19 K-K-pp events/month 27 K-K-pp events/month sK-K-pp = 8MeV sH = 25MeV sK-K-pp = 12MeV sH = 45MeV

34. Summary and Outlook

35. Summary • We propose to search for double strangeness production by pbar annihilation on helium nuclei at rest. • The proposed experiment will provide significant information on double strangeness production and double strangeness cluster states, like K-K-pp. Outlook • We are investigating further realistic estimation of the K+K0LL yield and the backgrounds. • We are now preparing the proposal for J-PARC based on the LoI.

37. Back-Up

38. Decay Particle Momenta H (MH=2*ML) E15 setup case K-K-pp (B.E.=200MeV) K0-p- K0-p+ L+L L-p L-p- K0Sp+p- :206MeV/c at rest Lpp- :101MeV/c at rest bgct(K+) = 0.75m @100MeV/c

39. Time Schedule • The proposed experiment will be scheduled in around JFY2014, • whether we conduct the experiment at K1.8BR or K1.1 beam-line. • K1.8BR : after E17/E15/L(1405)? • K1.1 : joint project with the fN experiment?