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Strange tribaryon: Experiments

HS05, KEK, 2005/12/2. Strange tribaryon: Experiments. H . Outa (RIKEN) for KEK-PS E471/E549/E570. Summary of 4 He(stopped K － ,p) / 4 He(stopped K － ,n) experiment (E471) Status of on-going experiments at KEK

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Strange tribaryon: Experiments

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  1. HS05, KEK, 2005/12/2 Strange tribaryon: Experiments H. Outa (RIKEN) for KEK-PS E471/E549/E570 • Summary of 4He(stopped K－,p) / 4He(stopped K－,n) • experiment (E471) • Status of on-goingexperiments at KEK • E549: 4He(stopped K－,N) w/ upgraded detectors • E570: K－ 4He X-ray measurement • 3. Experiments at J-PARC

  2. List of collaboration (E471/E549/E570) G. Beer, H. Bhang, M. Cargnelli, J. Chiba, S. Choi, G. Franklin, Y. Fukuda, K. Gomikawa, T. Hanaki, R.S. Hayano,T. Hayashi, M. Iio, K. Ishikawa, T. Ishikawa,S. Ishimoto, T. Ishiwatari, K. Itahashi, M. Iwasaki,B. Jihasz, T. Katayama, P. Kienle, Y. Kondo,J. Marton, Y. Matsuda, T. Nakamura, H. Ohnishi, S. Okada, H. Outa, C. Petrascu, B. Quinn, M. Sato, M. Shindo, H. So, P. Strasser, T. Sugimoto, K. Suzuki, T. Suzuki, H. Tatsuno, D. Tomono, A.M. Vinodkumar, E. Widmann, T. Yamazaki,H. Yim, T. Yoneyama, J. Zmeskal

  3. Quark-pair condensation？ T Big bang Higgs condensation T：~ 100GeV Quark mass ~MeV Quark-pair condensation T：~ 200MeV Quark mass ~300MeV Baryon formation Baryon mass ~0 Present universe T：~ 0 eV Baryon mass ~1000 MeV r 1

  4. Embedding Ｋ in nucles？ ・Deep! ～100 MeV cf: BN～10 MeV ・Narrow! ～20 MeV = meta-stable ・Shrink! K-nucleus bound state = high density? ☞hadron mass ☞astronomical study 2

  5. How to produce？ Missing mass measurement 4He Z : +1 T : 0 or 1 n ppnK- predicted unpredicted Z : 0 Ｔ　：　１ p pnnK- 3

  6. K beam & NC &TC Experimental setup of E471 KEK PS-E471 experiment at KEK-PS LC : K/p separation DC : K- beam trajectory • NC wall (TOF stop): • left/right of He • n, p detection • TOF distance ～ 2m • vertex (p,p) detector (TC): • above/below of He • DC & TC (2layer) • reaction vertex • PID TOF wall trigger condition M.Iwasaki : NIM A473(2001)286 4

  7. K- + 4He  S0 + p Detection threshold （due to Fe plate） 4He(stopped K-, p) spectrum 5

  8. Result of Proton ・distinct in proton ・semi-inclusive ! ・very narrow width Strange tribaryon S0(3115) P3 BG + Gaussian χ2/DOF = 8.76/12 Gaussian center: 3117.7 MeV/c2 Gaussian sigma: 8.7 MeV/c2 Statistical significance: S/ΔS = 2441/297= 8.2 σ 6

  9. Hyp. decay = should be in HERE! Hyp. decay = NO! Y Motion (relative to proton) 7

  10. Mass spectra proton data χ2/DOF = 28.52/31 Gaussian center: 3140.5 MeV/c2 Gaussian sigma: 7.3 MeV/c2 Statistical significance: S/ΔS=120/32= 3.7 σ neutron data nucl-ex/0310018 8

  11. Summary of E471 results ＊S+(3140) notconclusive ＊Only upper limits on widths ＊Large error on formation rate / mass 9

  12. What was observed ? - K bound nuclei？ ・We searched for this… ・Much different energy from the initial prediction ・Excited state? ・High density? Only the energy is known - nonaquark? Need further study !! ・H-dibaryon？ - pionic  Hypernucleus？ ・energy is close to π+Λ+nuclei … - Two-nucleon absorption？ ・K- + “d” → Σ- + p (back-to-back) ・Stopped d in  ? ・Too-high Σ energy (βγcτ～2cm) 11

  13. - one nucleon is in p-wave? A. Dote et al. : PLB590 (2004) 51 What is the situation？ (theory) (experiment) p n particle (other) K-3He atom E theory(isospin triplet) ~ Σ π threshold Binding energy theory (isospin singlet) ~ 200 MeV (isospin singlet) observed (isospin triplet) 10

  14. On-going experiments…. No new “results” now, sorry !!

  15. resolution improve 150ps→50ps Neutron counters 4 layers→7 layers Proton chamber Smaller target TOF Start counter （σ< 70ps) Proton TOF stop (σ～70ps) Veto counter for neutron detection Both proton/neutron σ～300ps proton σ=100～150ps neutron σ=200ps E549 run ( May.24th-Jul.1st) Upgrade in E549 E471 Setup Neutron counters Incoming K－ Incoming K－ proton proton neutron 4He target Iron plate Charged particle veto counter 12

  16. K- + 4He → (K- + pnn)[T=1] + p | 1/2 -1/2 > |1 -1> + |1/2 1/2> K- + 4He → (K- + ppn)[T=1] + n | 1/2 -1/2 > |1 0> + |1/2 -1/2> Formation ratio = 2:1 Goal of E549 run ① 4He(K-, p) S0(3115) position/width Error of energy～3MeV now 　　　　　　　　　　　 →　～1 MeV Width Limit→finite value (if Γ>10MeV) proton statistics >×30 times (inclusive) energy resolution ×2-3 times better ②　 4He(K-, n) Confirm S+(3140) Statistical significance ～ 10σ Contribution of T=0 states neutron statistics×8 times 1.5 times better energy resolution ③ 4He(K-, p)Search for excited states Direct evidence of high density １1 13

  17. Target Image(E549) – seen from SIDE chamber Vertex Z (mm) Calibration by (π,π’) scattering events 14

  18. Current status of E549 data analysis 1/b distribution from K+ TOF parameter tuning K+ decay mode 1/b (K+stop) event K+m+ n 1.1 K+p+p0 1.21 m (K+m2 ) K+e+p n 1 • TOF resolution • s(1/β) ~ 0.02 • (width of m peak) p (K+p2 ) e (K+e3 ) Mass resolution σ～4 MeV for S0 (3115) 1/ b 15

  19. Total light output VS 1/b K stopping time distribution Incoming K－ proton neutron Charged particle PID / Stop K selection • Identification of charged particle K- stop events Proton events are clearly separated Total Light Output (MeVee) p p m e d K- stop events 1/ b Accepted as Stopped K Event • Stopped K selection In-flight decay/reaction events are rejected In-flight reaction K- Stopping time (nsec) 16

  20. Neutron detection…. E549 very preliminary Background suppressed E471 very preliminary σ=0.039 Better S/N ratio Better resolution All the detectors are working well 17

  21. Kaonic Atom?? K-He = anomalous shift ?? Exp. = 40 eV !! (repulsive) cf. < 1 eV (potential) Kaonic Nuclei ? KN interaction ? We are measuring 3d→2p X-ray energy with ～a few eV accuracy (E570; from this Oct. ) 18

  22. E570 experiment • Use 8 SDDs • (Silicon Drift Detector) • - better resolution • σ>300 ⇒ ～150eV • - very thin (～300μm) • (2) Clean stopped K- on helium • events selection • w/ chamber tracking SDD ～10 times more peak statistics S/N～1 → 10 ～2 times improved resolution 19

  23. Preliminary result of Oct. run 4d→2p 3d→2p 20

  24. Experiments at J-PARC and other Lab.

  25. Kaonic nuclei experiments… Light target only = 4He, 3He Huge background especially from 2N-abs. Stopped K- K-Fragment method @ FINUDA K-pp Nagae’s group (In-flight K-,N ) Kishimoto’s group @BNL/KEK Heavy nuclei? Background seems to be not so seriousStable? (especially in nucleon side) Invariant-mass L-d invariant-mass d+p -> K+ + K-ppn 21

  26. K-“pp” L+p p p- Results of measurement on invariant mass GSI-FOPI inv. mass method preliminary, HPC2005 Data K-pp MC-sig MC-bg Ni+Ni @ 1.93AGeV:Λ+d(Kppn) B=149MeV, M = (3159 ± 20)MeV POOR SIGNAL/NOISE RATIO FINUDA 22 Phys. Rev. Lett. 94 212303 (3 June 2005)

  27. JPARC experiment Easy to carry out….. stop K In-flight reaction on Formation cross section ?? 23

  28. by Y. Akaisi ？ 24

  29. Complete measurement on few-body system 3He target Spectator? Related to FINUDA DATA Exclusive measurement of all the particles emitted in formation & decay = charged particles 25

  30. Dalitz Plot 26

  31. J-PARC Setup Ｓ＝ -１ ・1 GeV/c line ・ Measure both of formation and decay ・ Both of (K-,p) and (K-,n) ・ Both of missing mass/ invariant mass method 27

  32. Summary • We discovered strange tribaryon S0(3115) with • total isospin T=1 in the 4He(K-stopped, p) • reaction. 2.New experiments(E549/E570) are on-going at KEK-PS E549: 4He(stopped K-,p/n) w/improved statistics/resolution E570: K-4He 3d→2p X ray with a few eV accuracy 3.Experiments at J-PARC - Light 3He target / exclusive measurement - Both of formation (missing mass)/ｄｅｃａｙ(ｉｎｖ.mass) study; detector to identify Σ/Λ

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