Search for Double Antikaon Production in Nuclei by Stopped Antiproton Annihilation

1. Searchfor Double Antikaon Productionin Nuclei byStopped Antiproton AnnihilationP. Kienle, Excellence Cluster Universe, TU München Introduction into the search for double kaonic nuclear cluster production by stopped antiproton annihilation Experimental approach @ J-PARC Experimental approach @ AD and FAIR

2. A Proposal forthe CERN AD

3. Letter ofIntentfor J-PARC

4. Possibility of “Double-Kaonic Nuclear Cluster” Production by Stopped-pbarAnnihilation Preludeto „Double-Strange Nuclei“ @ LEAP W. Weise, arXiv: 0507.058 (nucl-th) 2005 P. Kienle, J. Mod. Phys., A22 (2007) 365 P. Kienle, J. Mod. Phys., E16 (2007) 905 J. Zmeskal et al. EXA/LEAP 08, Hyper, Int J. Zmeskal et al. „Double-Strangeness Pro- ductionby Antiprotons, May 2009, CERN

6. DeeplyBound Di-Baryon Resonance with Strangness S =-1 • Properties • p+p -> K+ +X @ highmomentumtransfer • MX = 2.265 (2) GeV/c² -> BX = 105(2) MeV • ΓX = 118(8) MeV/c² • Assignedtodeeplybound, denseK-ppclusterwithBxabouttwicethevaluepredictedby AY • High observedproductionprobabilityispredictedbythe AY reaction model forthecaseof a highdensitycluster X • Consequencesfor Double Strange Cluster • Higher bindingenergyandhigherdensityexpectedcomparedwithsinglestrangecluster • T. Yamazaki et al.Hyp. Inter.DO: 10.1007/ s 10751-0099997-5

7. Double-Kaonic Nuclear Cluster • Double-kaonic nuclear clusters have been predicted theoretically. • Double-kaonic clusters are expected to have a stronger binding • energy and a 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

8. 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 deeply bound multi kaonic nuclear clusters exist, production by pbarannihilation reactions will be possible! theoretical prediction B.E.=117MeV G=35MeV B.E.=221MeV G=37MeV

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

10. A double-strangeness production yield of ~10-4would make it possible to explore the exotic systems with a dedicated experiment Experimental Approach for J-PARC

11. Searchforthe Most Elementary K-K-pp System In the following discussion, we focus on 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 detect the K-K-pp signal with: • exclusive measurement • all charged particles, K+K0LL, using K0p+p- mode • K0LL, and K+ ID using K0LL missing mass • (semi-)exclusive measurement • K+K0 missing mass with L-tag • LL invariant mass We need wide-acceptance detectors.

12. Expected Kinematics • assumptions: • widths of K-K-pp/H = 0 • many-body decay = isotropic decay K+ K0 X 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.

13. 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 pbar production yield with a Sanford-Wang pbar stopping-rate

14. 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

15. Detector Design I • 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

16. Detector Design II 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

17. Expected Signals LL inv-mass with NEW setup LL inv-mass with E15 setup 53 K-K-pp events/month 42 K-K-pp events/month sK-K-pp = 27MeV sH = 0.7MeV sK-K-pp = 34MeV sH = 14MeV Backgrounds from S0gL have to be taken into account K+K0 miss-mass with NEW setup K+K0 miss-mass with E15 setup sK-K-pp = 8MeV sH = 25MeV sK-K-pp = 12MeV sH = 45MeV 17 K-K-pp events/month 24 K-K-pp events/month

18. 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 for (semi-)inclusive measurements. • We are now preparing the proposal for J-PARC based on the LoI.

19. Experimental Approach for AD of CERN and FAIR

24. ThanksforYour Attention

25. 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

26. DIANA RESULTS • 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

27. OBELIX RESULTS • 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

28. Expected Kinematics II 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

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

30. Expected Signals I • 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 : inclusive events K+K0 missing mass : semi-inclusive events (w/ one more L)

32. K+K0ΛΛFinal 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