Search for Exotic Hadrons, H-dibaryon resonance and Pentaquark Kenichi Imai (JAEA(Tokai)) Past lessons (experiments ) H-resonance: KEK-E224, E522, BNL-E886 Pentaquark Q+ and L(1405): Spring-8, KEK-E522,E559 Future prospects: Experiments at J-PARC

BNL-E885 12C(K-,K+) K.Yamamoto et al., Phys. Lett. B478 (2000) 401.

X-hypernuclei ? BNL E885 12C(K-,K+) potential ~14MeV J-PARC E05 (T.Nagae) K1.8 and new SKS 12C(K-,K+) DM~2MeV spectroscopy of X hypernuclei 2008/12/15 Sendai08

Lamdpha(6HeLL) -> DBLL=1MeV 10BeLL

LL-Enhancement by the KEK-E224 J.K.Ahn et al., Phys. Lett. B444,267(1998) K s (1) H-dibaryon Resonance? K-p->X-K+; X-(p) -> H, H->LL (2) Strong LL Final State Interaction?

- SCIFI active target 20 cm

LL invariant mass (KEK-E522) C.J.Yoon et al., PRC75 (2007) 022201 Afss2 is consistent with DBLL=1.0 MeV obtained by Nagara event f

J-PARC Japanese-French Symposium (Paris 2008.9.29)

Hadron Experimental Hall Beam Line Layout Plan SKS+ K1.8 K1.8BR K1.8ES2 T1 K1.8ES1 Primary Beam Beam Dump KL-B1 KL K1.1 K1.1BR

K1.8 beam line and SKS spectrometer 2019/2/21

S- Missing mass spectrum @LH2 preliminary preliminary S- S- Expanded ~7.8×109 p- data, ~8500 counts DM = 1.99±0.05 MeV (FWHM) 2019/2/21

Detectors near target 4p and high rate capability -> TPC 2019/2/21

Experimental setup at SPring-8/LEPS 1.5 g E // B

Event Display run29666, ev 410, July 2004 run29666, ev 121, July 2004 2 February 2005

TPC at K1.8 in J-PARC for 100x LL, Q+, and L(1405)

Summary We have found a “peak structure” near threshold in LL mass spectrum in E224 and E522. Within statistics, the data can be explained with LL final state interaction which is consistent with weak attractive LL “binding” energy determined from the 6HeLL. However, the H-dibaryon resonance is still a possible interpretation of the peak. Much higher statistics and mass resolution is needed for a J-PARC experiment to finalize H-problem.

Pentaquark search at KEK-PS E522 and E559 1.92GeV/c  KEK-E559 (high resolution) K+p->p-Q+ upper limit ~3.5mb  p  K + upper limit 3.9b (90% C.L.) K.Miwa et al.,　Phys. Lett. B635 (2006) K.Miwa et al., Phys. Rev C77 (2008) E522 E559

Upper limit of cross section 1.92GeV/c CH2 target  < 4.1b(90% C. L.) 1.87GeV/c CH2 target  < 2.3b(90% C. L.) SCIFI targert  < 2.5b(90% C. L.) Assume s-wave  10.8% of K accepted fbeam=83%(e, contamination 13%,  reaction 4%) eK2=72.3% eDAQ=94% fKabs=89.8% etrack=84.6% fdecay=57.6% fcherenkov=91% eMT=95.7% eana=51% d=0.14sr

S+p- and S-p+ spectra (L(1405) -> S+-p-+) Solid: this work Open: previous (Ahn) Different angular aceptance Sum M.Niiyama et al, PR C78 (2008)

2nd Summary We have searched for Pentaquark Q+ by p and K beam at KEK-PS No evidence was observed within statistics. E19 will provide 100x statistics and much better resolution (a few MeV resolution) L(1405) will be studied with high statistics.