E19 result Ryuta Kiuchi (SNU) -- on behalf of E19 collaboration and J-PARC hadron beam line staffs and users Ryuta Kiuchi (SNU) “ Korea-Japan workshop on nuclear and hadron physics at J-PARC” 09.22.2011 @ Seoul National University

E19 and Pentaquark search E19 @ J-PARC aim to search Θ+ pentaquark resonance via (π-, K-) reaction using high intensity beam line & good mass resolution ### Pentaquark is a hypothetical particle consisting of four quarks and one anti-quark

Past experiments of Penta-quark search LEPS collaboration , Nakano et.al, K. Miwa et.al.,Phys. Lett. B. 635, 72 (2006) E552 suggest the existence of Θ+ at 1.53GeV/c2

K1.8 Experimental Area SKS Spectrometer K1.8 Beam Spectrometer Q13 Q12 D4 Q11 Q10

Current Setup ・ Beam spectrometer ・ SKS spectrometer Beam spectrometer (SKS0 configuration) ・ Beam spectrometer Trigger Counter : -- BH1, BH2 (Hodoscope) -- eGC (e/p ,Cherenkov) -- BAC (p/K, K/p , Cherenkov) Tracking Chamber: eGC -- BC1, BC2 (MWPC) -- BC3, BC4 (MWDC) SKS spectrometer ・ SKS spectrometer SKS magnet : Typ. 2.2T (300A) , Central Mom. 0.75GeV/c Trigger PID Counter : -- TOF wall (32seg.) -- LC wall (28seg.) -- AC (p/K , Cherenkov ) Tracking Chamber: -- SDC1, SDC2, SDC3, SDC4 (MWDC)

Data Summary Ʃ+ 1.37 (π+, K+) LH2 2.9 5 Ʃ- (π-, K+) 12 20 Empty 1.92 Term : 2010.10 ~ 2010.11 Mom [GeV/c] Reaction Target Number of Beam particle Data taking hours Ʃ+ 1.37 (π+, K+) LH2 2.9 5 Ʃ- (π-, K+) 12 20 Empty 1.92 (π-, K-) -- 4.6 10 Θ+ 78 132 ### Empty run == without LH2 but target cell was exist We have accumulated 10 times more statistics than E522 exp.

Vertex reconstruction Y Target cell Z Beam Beam

Vertex reconstruction -- comparing with empty run data Z X LH2 Y Empty Target cell Z Empty target data @ 1.92 GeV/c ~3 % background in the selected region (Empty data : Normalized by beam flux)

Calibration run -- Ʃ+/- production p(p+, K+)S+ run @ 1.37 GeV/c p(p-, K+)S- run @ 1.37 GeV/c

Missing mass resolution Estimated from S data & simulation DM =1.86 MeV/c2 (FWHM) S+ DBeam DSKS Dq DE DM MeV S+ 0.42 1.66 0.46 0.56 1.86 Q+ 0.53 1.17 0.50 0.41 1.44 @ q=5 ° S±: DMS = 1.9 ± 0.1 MeV/c2 (FWHN) ⇒Q+ missing mass resolution DMQ = 1.4 ± 0.1 MeV/c2 (FWMH) (DM ∝ Mtarget/MQ)

Missing mass spectrum Preliminary All event sum : 7.8×1010 p- p- + p → K- + X @ 1.92 GeV/c Preliminary ＊If exists MQ ~ 1.53 GeV/c2 All event sum : 7.8×1010 p- With event selection 2°< qscat.< 15°& vertex cut e.t.c No prominent peak structure observed.

Comparison with background simulation BG reactions p- p → fn→K- K+ n (s = 30±8 mb) p- p → L(1520) K0 →K- K0 p (s = 21±5 mb) p- p →K- K+ n p- p →K- K0 p (s ~25 mb) O. I. Dahl et al . Phys. Rev. B 163, 1377 (1967). (Bubble chamber data) Simulation with measured cross section. Cross section error : 20~30%

Comparison with background simulation Data BG reactions p- p → fn→K- K+ n (s = 30±8 mb) p- p → L(1520) K0 →K- K0 p (s = 21±5 mb) p- p →K- K+ n p- p →K- K0 p (s ~25 mb) Sim (×1.0) Sim (×1.2) O. I. Dahl et al . Phys. Rev. B 163, 1377 (1967). (Bubble chamber data) Simulation with measured cross section. Cross section error : 20~30%

Differential cross section Preliminary Differential cross section (Averaged 2°-15°) ⇒Obtain 90 % confidence level upper limit Width : 1.4 MeV/c2 fixed (Estimated S data)

Upper limit of cross section Differential cross section Scanning region 1.51-1.55 GeV/c2 BG shape ⇒ 3rd order polynomial Peak shape ⇒ Gaussian (s=1.4 MeV/c2 fixed) Preliminary Differential cross section (Averaged 2°-15°) ⇒Obtain 90 % confidence level upper limit Width : 1.4 MeV/c2 fixed (Estimated S data)

Upper limit of cross section Preliminary Preliminary Upper limit cross section : < 300 nb/sr @ 1.52-1.54 GeV/c2 Cross section @ if MQ = 1.53 GeV/c2 Differential : 100 nb/sr (averaged 2°-15°) Evaluation of systematic errors is ongoing.

Summary ・ J-PARC E19 experiment, search for penta-quark state via p- p → K- Q+ reaction, was done in 2010 October/November with 10 times higher statics than E552. ・ Preliminary analysis results shows no remarkable signals around 1.51-1.54 GeV/c2 . ・ Now we are improving analysis method, and also preparing a paper. ・ We will take data with the incident pion beam momentum of 2.0 GeV/c again.

Present status of Q+ After LEPS collaboration report ⇒Many positive results & Many negative results Positive results LEPS new report : g d →p K- K+ n CLAS(p) : g p→p+ K- Q+→p+ K- K+ n DIANA : K+ n →Q+→K0 p Negative results High energy experiments CLAS : g d→p K- Q+→p K- K+ n ＊High statistics & high sensitivity ⇒Controversial situation ＊Low energy hadron reaction (p or K beam) Few data Expected larger production cross section ⇒ Essential part for the investigation of Q+ DIANA CLAS

Cross section Tracking part Counter, PID part Other part Target Beam Other analysis SKS Tracking part BC1&2, BC3&4, SDC1&2, SDC3&4, K1.8, SKS Single track selection Counter, PID part Beam p selection, TOF, LC, AC, scattered K selection Other part Decay, absorption, vertex, matrix trigger, acceptance

Cross section Tracking part Counter, PID part Other part Target Beam Other analysis SKS Tracking part BC1&2, BC3&4, SDC1&2, SDC3&4, K1.8, SKS Single track selection Counter, PID part Beam p selection, TOF, LC, AC, scattered K selection Other part Decay, absorption, vertex, matrix trigger, acceptance

Missing mass S+ S- Missing mass resolution : ~2 MeV/c2 (FWHM)

Missing Mass Resolution