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Strange multibaryons studied in the 4 He(K - stopped , L N) reaction

Strange multibaryons studied in the 4 He(K - stopped , L N) reaction. 1. Introduction 2. Experiment 3.  N correlations 4.  N +n semi-exclusive analysis 5. Conclusions. Takatoshi Suzuki (The University of Tokyo)

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Strange multibaryons studied in the 4 He(K - stopped , L N) reaction

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  1. Strange multibaryons studied in the 4He(K-stopped, LN) reaction 1. Introduction 2. Experiment 3. N correlations 4. N +n semi-exclusive analysis 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. BNL-AGS E930 (T. Kishimoto et. al., 2001) with 16O(in-flight K-,n) -> narrow bound state(s)? (NPA 754 383c (2005)) KEK-PS E548 (T. Kishimoto et. 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 (2002), PLB 535 70 (2002)) 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. Bressani et. 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. Ymazaki et. 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. Hayano et. 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. Yim et. 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) 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. 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/YdX exclusive data. Momentum decision by track detection+TOF method for pn-> remarkable momentum resolutions and PID for p/n/d

  8. 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

  9. ~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%

  10. Possible Interpretation of bp component Possible contibutions to component bp… 1. branch of“two”-nucleon absorption and possible successive  conversion process (FSI) K-‘NN’ -> p  ‘N’ -> p Contribution from K-‘pp’ -> p  ->  2. pn/pnn branch of “three- or four-nucleon absorption” cf. PRC 76 068202 K-‘ppn’ -> pn , K-‘ppnn’ -> pnn 3. 2S+T=1/2 dibaryon (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=1 tribaryon(=K-pnn ) production and its nn/S0nn decay K-stopped + 4He ->3S0T=1+ p 3S0T=1->+ n + n

  11. The existence of three- and four-nucleon absorption processes of K- were also established in KEK E549… Three- and Four-Nucleon Absorption K-stopped + 4He -> “n”+ d + L Condition: pd > 550 MeV/c pL > 350 MeV/c cosqLd<-0.8 K-stopped + 4He -> t + L 4NA(Lt Br.) : 0.03%/K-stopped 3NA(Ld Br.) : ~0.1%/K-stopped Three- and four-nucleon absorption processes do exist, but too rare to account for intense “B” components.

  12. 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% 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 and S0 decay).

  13. 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 3S0 tribaryon. Ln+n

  14. 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 (S0 nn 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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