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Strange Multibaryons Studied in the 4 He(K - stopped , YN) Reaction

Strange Multibaryons Studied in the 4 He(K - stopped , YN) Reaction. 1. Introduction 2. Experiment 3.   N correlations and normalized  p spectra 4.  N + n semi-exclusive analysis and S 0 p spectra 5. S - p correlations 5. Conclusions. Takatoshi Suzuki

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Strange Multibaryons Studied in the 4 He(K - stopped , YN) Reaction

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  1. Strange Multibaryons Studied in the 4He(K-stopped, YN) Reaction 1. Introduction 2. Experiment 3.N correlations and normalized pspectra 4.N +n semi-exclusive analysis and S0p spectra 5. S-p correlations 5. Conclusions Takatoshi Suzuki (The University of Tokyo) for KEK-PS E549 collaboration

  2. KEK-PS E549 collaboration H. Bhang, J. Chiba, S. Choi, Y. Fukuda, T. Hanaki, R. S. Hayano, M. Iio, T. Ishikawa, S. Ishimoto, T. Ishiwatari, K. Itahashi, M. Iwai, M. Iwasaki*, P. Kienle, J. H. Kim, Y. Matsuda, H. Ohnishi, S. Okada, H. Outa, M. Sato, S. Suzuki, T. Suzuki, D. Tomono, E. Widmann, T. Yamazaki, H. Yim

  3. Introduction -Do deeply bound kaonic nuclear states with narrow widths exist ? Prediction 1 : T. Kishimoto(PRL 83 4701 (1999)) -> No, they don’t! They must be shallow and broad -> Yes, they do. ”DD” potential by Friedman-Gal BNL-AGS E930 (T. Kishimotoet. al., 2001) with 16O(in-flight K-,n) -> narrow bound state(s)? (NPA 754 383c (2005)) KEK-PS E548 (T. Kishimotoet. al., 2005) with 16O/12C (in-flight K-,N) -> no narrow sates ! but deep potential (PTP 118 181 (2007), NPA 827 321c (2009)) Prediction 2 : Y. Akaishi and T. Yamazaki (PRC 65 044005, PLB 535 70 (2002) “Super strong” nuclear force KEK-PS E471 (M. Iwasaki et. al., 2002/2003) with 4He(stopped K-,N) -> observation of “strange tribaryons”(nucl-ex/0310018,PLB 597 263 (2004)) FINUDA (T. Bressaniet. al., 2003/2004/2006) with 6/7Li/ 12C(stopped K-,p/d) -> evidence for deeply bound ppK- /ppnK-state(PRL 94 210323 (2005), PLB 654 80 (2007) ) DISTO (Re-analysis by T.Ymazakiet. al. ) with pp->pLK+ at 2.85 GeV ->indication of ppK- bound state (PRL 104 132502 (2010)) KEK-PS E549/570 (M. Iwasaki et. al./R. S. Hayanoet. al., 2005) with 4He(stopped K-,N) -> no narrow sates !(PLB 659 107 (2008) , PLB 688 43 (2010) ) Broad states with 4He(stopped K-,LN)? -> This talk

  4. Original aim of KEK-E549- Inclusive spectroscopy (K-stopped, p) (semi-)Inclusive missing mass spectroscopy of (KbarNNN)Z=0,T=1 : S0 / (KbarNNN)Z=1,T=0,1 : S+ via K-stopped + 4He -> p + S0T=1 -> n + S+T=0,1 S+T=0,1 -> Y()NN Y -> N ->M. Sato et. al., PLB 659 107 ->H. Yimet. al., PLB 688 43 ✓ Very strict upper limits for narrow( ≤ 20 MeV/c2)states. ✓Insensitive to broad ( ≥ 40 MeV/c2) states. Large upper limits at ~3140 MeV/c2 for ≥ 40 MeV/c2. (K-stopped, n)

  5. Semi-exclusive studies -from non-mesonic final states Semi-exclusive missing mass spectroscopy via K-stopped + 4He -> N + 3S0/+T=0,1 3S0/+T=0,1 -> YNN Y:->arXiv:0711.4943 Small statistics, but well resolved final states. Dibaryon? K-stopped + 4He -> 2S0/+T=1/2,3/2+ N + N 2S0/+T=1/2,3/2-> YN Inclusive measurement for K-stopped + 4He -> 2S0 T=1/2+ d Y:->PRC 76 068202 (2007) arXiv:1009.5082 Semi-exclusive measurement for K-stopped + 4He -> 2S0T=1/2+ d 2S0 T=1/2->Yn -> 3S+ T=0,1+ n 3S+ T=0,1->Yd

  6. Only total capture rate is known. Dynamical nature is Speculative. Stopped K-Reaction on 4He

  7. Our Strategies Step 1. Does the Two-Nucleon Absorption Process, K- ‘NN’(NN) -> YN (NN) exist on A>2 nuclei? How is the dynamical property if it exists?? This is closely related to the kaonic nuclear search, as i) it behaves as so far unkown background, and ii) non-mesonic decay mode of kaonic nucleus, to which experimental searches are mainly performed, is no more than two(or multi)-nucleon absorption at negative energy - therefore the decay branching ratio is bound by the spin-isospin property at 0-energy. Step 2.Does the multibaryonic intensity, which is clearly separable from the contribution of multi-nucleon absorption process, exist?

  8. p/n/ N/d  N K-  Measurement E549 June 2005 1×108 stopped K- E570-1 October 2005 1×108 stopped K- E570-2 December 2005 4×107 stopped K- inclusive data of N/d　＋YNX/YdXexclusive data. Momentum decision by track detection+TOF method for pn-> remarkable momentum resolutions and PID for p/n/d

  9. Accuracies of angle momentum scales, and sensitivity 1.3±0.2(stat) ±0.2(syst) ×10-5 / K-stopped H. Outaet al., to be submitted soon We have successfully observed the two-body NMWD of 4He-Lambda hyper nucleus via K-stopped + 4He -> p- + 4LHe 4LHe -> d+ d The events cluster well at cos(dd) < -0.99, as simulated. 1. High resolution and no systematic on the opening angle. 2. Precise mass scale. 3. Sensitive to the processes with very tiny fractions.

  10. N Invariant Mass Spectra (cp/n):quasi-free hyperon production(+conversion for ) K- ‘N’ ->  (+‘N’ -> )  (ap/n):two-nucleon absorption K- ‘NN’ ->  (bp/n):non-mesonic. But ?? They could be the signal of multibaryon S0 contribution is supposed.

  11. N correlations (2) n p 1. ‘NN’I=0,S=1 dominance of K- ‘NN’I,S ->  ~0.9%/K-stopped ~3%/K-stopped 2.More intense contribution of Bp/n

  12. N correlations (3) p n (bp/n) -> broad strength peaked at ~470 MeV/c. ✓ K-NN(NN) -> LN(NN) : two-nucleon absorption followed by only one of N(N) -> NN or L (N) -> LN : elastic rescattering is unlikely, to account for L and N momentum distributions both shifted. L and N momenta are seen to be lower at the same time.

  13. MM(N) VS IM(YN) plots ✔ Ap/n (Two-Nucleon-Absorption) produces continuum BG as expected at tribaryon mass~3070 MeV/c2 • Bp/npeaks at tribaryon mass~3140 MeV/c2 (B.E. 170 MeV), • dibaryonmass ? -> S0 contribution must be checked.

  14. ~3150 MeV/c2 BK-pnn ~ 160 MeV Normalized Lp spectra Condition: pp> 320 MeV/c pL> 320 MeV/c cosqLp<-0.75 Now, spectra are comparable to any theoretical calculation. Note that S0 contribution is not negligible (later). Branching fractions: Ap:0.9%/K-stopped Bp:1.3%/K-stopped ~2230 MeV/c2 BK-pp ~ 140 MeV 1.3% K-pnn interpretation: BK-pnn ~ 160 MeV GK-pnn > 100 MeV K-pp interpretation: BK-pp ~ 140 MeV GK-pp ~ 70 MeV 0.9%

  15. Possible Interpretation of bp component Possible contibutions to component bp… 1.branchof“two”-nucleon absorption + (A) possible successive conversion process (FSI) K-‘NN’ -> p ‘N’ -> p (B) EM decay of 0 K-‘pp’ -> p  ->  2. pn/pnnbranch of “three- or four-nucleon absorption” cf. PRC 76 068202 K-‘ppn’-> pn , K-‘ppnn’ -> pnn 3. 2S+T=1/2dibaryon (K- [pp] I=1,S=0) production and its p decay (for 6Li + 7Li + 12C, FINUDA collaboration, PRL 94 (2005) 212303) K-stopped + 4He -> 2S+ T=1/2+ n + n 2S+ T=1/2->+p 4. 3S0T=1tribaryon(=K-pnn ) production and its nn and/or S0nn decay K-stopped + 4He ->3S0T=1+ p 3S0T=1->/S0+ n + n

  16. The existence of three- and four-nucleon absorption processes of K-were also established in KEK E549… Three- and Four-Nucleon Absorption cosqLt<-0.99 K-stopped + 4He -> “n”+ d + L K-stopped + 4He -> t + L Condition: pd > 550 MeV/c pL> 350 MeV/c cosqLd<-0.8 4NA(Lt Br.) : 0.03%/K-stopped 3NA(Ld Br.) : ~0.1%/K-stopped Three- and four-nucleon absorption processes do exist, buttoo rare to account for intense “B” components. Of course , they occur more sparsely than 2NA as the experimental fact. See, arXiv:1009.5082

  17. LN+n semi-exclusive analysis 1 – separation of S0 and L final states Lp+n Lp+n Ln+n Ln+n LpNNN S0NNN LNNN • ✓By detecting an additional neutron in coincidence with back-to-back LN, • we can successfully separate LNNN/LgNNN/LpNNN final states. • 30~50% of Bp component is now found to be occupied by S0pnn events. • Study of S0pnn events allows us more unambiguous search of multibaryon intensity (No contribution of SL conversion).

  18. Possible Contribution to S0p spectra Possible contributions to S0p spectra from non-mesonic S0pnn final state… 1. 0p branch of“two”-nucleon absorption + EM decay of 0 Conventional, supposed to be the largest. K-‘pp’ -> p ->  2.S0pn/S0pnnbranch of “three- or four-nucleon absorption” K-‘ppn’->S0pn , K-‘ppnn’ -> S0pnn Smaller than 2NA 3. 2S+T=1/2dibaryon (K- [pp] I=1,S=0) production and itsS0p decay ?? K-stopped + 4He -> 2S+ T=1/2+ n + n 2S+ T=1/2->S0+p 4. 3S0T=1tribaryon(=K-pnn ) production and its S0nn decay ?? K-stopped + 4He ->3S0T=1+ p 3S0T=1->S0+ n + n

  19. LN+n semi-exclusive analysis 2 – observation of multibaryon strength Green :S0NNN Red :LNNN K-stopped + 4He -> S0+p+”nn” K-stopped + 4He -> L+p+”nn” • No 2NA strength is seen for S0pevents. • Peak of tribaryon mass spectrum by S0p final • state is shifted from expectation of 2NA process by ~40 MeV/c2 !! Lp+n • Any conventional explanation cannot account for the intensity • centered at 3170 MeV/c2 . K-stopped + 4He -> S0+n+”pn” K-stopped + 4He -> L+n+”pn” ->Observation of S0nn decay mode of 3S0tribaryon =K-pnn Ln+n

  20. p correlations (1) ~1%/K-stopped

  21. p correlations (2) 2NA: ~1 % out of 3.6 +- 0.9 % of -ppn/-pd final state - momentum distribution for non-2NA component is never explained by elastic re- scattering!!! K-stopped + 4He -> 2S0T=1/2 (K- [pn ] I=0,S=1)+ p + n 2S0T=1/2->+p -> 3S0T=1 + p 3S0T=1->+pn/d

  22. Supports for the tribaryonic interpretation… ✔Sudden jump of the total fraction and L/S ratio of the non-mesonic final states of the stopped K- reaction from d to 4He: SL conversion can change the observedSL ratio. Deeply bound Kaonic nucleus can also by phase-space effect. But No FSI can explain the behavior of the total non-mesonic fraction. Kaonic nucleus can change it by density and phase-space effect. ✔Small G2p of the Kaonic4He atom (KEK E570:UL 17 eV (95% CL) : NPA 827 324c (2009) ) -> Expected tribaryon yield (Wf,i=1.2eV)/(G2p) is now expected to be >7%!!

  23. Conclusions 2. The 2NA process accounts for only ~30% of non-mesonic branch. 1. The LN branch of 2NA process of negative kaon has been very clearly observed. 3. We confirmed that 30~50% of remaining non-mesonic branch of 7~8%/K-stopped are actually occupied by S0pnn final state. 4. HOWEVER, the source of S0p events are NOT the S0p branch of 2NA process, andno 2NA was observed in the S0p events. Therefore, any process cannot account for the intensity expect for di-/tri-baryons. 5. Observed3S0(=K-pnn) mass is ~3150 MeV/c2 (S0nn and Lnn modes overlap). The spectrum shift between Lp and S0p final states can be interpreted as the dependence of the spectrum functions on the decay mode of tribaryons.

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