1. 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

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

3. 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

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

5. 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?

6. -
SCIFI active target
20 cm

7. 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

8. J-PARC
Japanese-French Symposium (Paris )

9. 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

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

11. 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

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

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

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

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

16. 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.

17. 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)
E E559

18. 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

19. 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)

20. 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.