Search for pentaquark Θ + in hadronic reaction at J-PARC. M. Naruki for the E19 collaboration 2012/8/24 FB20, Fukuoka

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1 Search for pentaquark Θ + in hadronic reaction at J-PARC M. Naruki for the E19 collaboration 2012/8/24 FB20, Fukuoka 1

2 Outline Introduction o Overview of pentaquark Θ + searches o J-PARC E19 experiment Recent results o result of the 1 st data o recent result of 2 nd data Summary 2

3 Exotic Hadron a tool for investigating quark dynamics inside the hadron. o excitation of constituent quarks? To what extent is the constituent quark model applicable for the observed states? o hadronic molecules? ex. Λ(1405) o diquark clustering, or something else? We have already clues. o exotic mesons from B-factories o pentaquark Θ + 3

4 Search for pentaquark Q + Q + (uudds) : explicitly exotic 5- quark state First discovery from LEPS o n Q n o M= MeV o <25 MeV many positive results with significance of ~5σ many negative results with high statistics o few experiments in hadronic reactions LEPS 03 4

5 Positive Results LEPS DIANA CLAS-d SAPHIR ITEP 3.6 CLAS-p 4.9 HERMES 3.6 ZEUS 4~5 COSY-TOF 4.7 SVD 4.4 Experiments with positive evidence significance = S/ (S+B) or S/dS better statistics is needed 5

6 Positive Results LEPS 5.1 DIANA 5.5 CLAS-d ITEP 3.6 CLAS-p 4.9 HERMES 3.6 ZEUS 4~6 COSY-TOF Experiments with positive evidence SVD 5.8 significance = S/ (S+B) or S/dS ~ 5σ better statistics is needed 6

7 Positive Results LEPS DIANA 5.5 CLAS-d ITEP 3.6 CLAS-p 4.9 HERMES 3.6 ZEUS 4~6 COSY-TOF Experiments with positive evidence SVD 5.8 significance = S/ (S+B) or S/dS ~ 5σ better statistics is needed 7

8 Positive Results LEPS DIANA 5.5 CLAS-d ITEP 3.6 CLAS-p 4.9 HERMES 3.6 ZEUS 4~6 COSY-TOF Experiments with positive evidence SVD 5.8 significance = S/ (S+B) or S/dS ~ 5σ better statistics is needed 8

9 Negative Results Exp. s(e beam ) Reaction Upper Limit BES 3.7GeV e + e J/ψ ΘΘ < B.R. BaBar 10.58GeV e + e Υ(4S) pk 0 X < B.R. Belle 11GeV e + e BB ppk 0 X < B.R. ALEPH 198GeV e + e Z pk 0 X < B.R. HERA-B 41.6GeV pa K 0 px < 0.02 Λ * SPHINX 11.5GeV pc K 0 Θ + X < 0.1 Λ * HyperCP (800GeV) pcu K 0 px < 0.3% K 0 p CDF 1.96TeV pp K 0 px < 0.03 Λ * FOCUS 300GeV γbeo K 0 px < 0.02 Σ * Belle (~0.6GeV) K + A pk 0 s Γ < 0.64 MeV PHENIX 200GeV Au + Au K nx - BaBar 9.4GeV ebe K 0 px - WA GeV Σ + A K 0 px 1.8mb/nucleon 9

10 Room for Θ+ Is there any explanation of null results, if it exists? production in fragmentation is suppressed. production is suppressed at high energy. Opposite results LEPS & CLAS in γn K Θ + o dσ/dω=12nb/sr σ<3nb o angular distribution & different acceptance DIANA & Belle in K + n Θ + o Γ=0.39±0.10MeV Γ< 0.64 MeV SAPHIR & CLAS in γp K 0 Θ + o Θ/Λ*~1/6 Θ/Λ*<0.01, σ<0.8nb o coupling to K*N is small SVD-2 & SPHINX in pa Θ + X o σ~6μb/a σ<30nb/a o different acceptance in xf. signal is enhanced in small xf. 10

11 Search for Pentaquark Q in p p X reaction exclusive, only s-channel process contributes background processes well studied. no strong angular dependence sizable cross section σ(π p K Θ + ) ~ 1μb π - K - n proton Θ + show the narrow pentaquark really exist (or not). with high statistics. determine the width with high resolution: dm=~2mev w/ SKS 11

12 KEK-PS E522 experiment Θ + search via π p K X reaction p π = 1.87, 1.92 GeV/c target : polyethylene intensity : 3.3 X 10 5 π /spill ~ 7 X 10 9 π on target dm = 13.4MeV(FWHM) a bump was observed at M =1530.8MeV/c2 at p p =1.92 GeV/c but : S/N = 2.5σ upper limit : ds/dω < 2.9μb/sr p π =1.92 GeV/c if exist, dσ/dω = 1.9 μb/sr 12

13 J-PARC E19 search for Θ + in p(π, K ) at K1.8 beamline target : liquid H2, ρ=0.86g/cm 2 beam momentum : p π =(1.87,1.92, 2.00GeV/c) 4.8 x π on target for each p π beam intensity : 10 7 /spill(2sec.) beam time : 160 hours SKS : ΔM = 2MeV FWHM Sensitivity : 75nb/sr SKS weight: 280 tons Magnetic Field: 2.5T Acceptance : 0.1sr 13

14 Liquid Hydrogen Target Q13 Q12 D4 Q10 Q11 14

15 Oct History o beamline & detector commissioning for 4 days Oct.-Nov (E19 Step1) o examine the bump structure observed in E522 experiment at p p =1.92GeV/c o accumulate of beam p on target in 156 hrs. (incl. 15hrs downtime) Feb (E19 Step2) o new data at the highest beam momentum of 2GeV/c o accumulate of beam p on target in 135 hrs. (incl. 35hrs downtime) 15

16 K1.8 Beam Spectrometer momentum analysis o 2 MWPCs & 2 DCs cope with 10MHz beam position resolution : 200μm tracking efficiency : 93% PID o e/π : Gas Cerenkov counter w/ Isobutane electron rejection power : 99.5% o π/k/p : TOF counters resolution : 140ps p : 1.92 GeV/c momentum bite : ~1% momentum (GeV/c) all detectors worked well & show enough performance. 16

17 SKS Performance SKS magnet o successfully operated up to 2.5 T at 400 A. Tracking Chambers o resolution : 250μm o tracking efficiencies : 96% Particle Identification o TOF : resolution 150ps o KID efficiency : 83% Enough performance has been achieved. M 2 spectrum of scattered particles Mass square [(GeV/c 2 ) 2 ] 17

18 Spectrometer Performance Σ + production o in p(π +,K + ) reaction Σ o Target : Liquid Hydrogen o p beam : GeV/c ΔM = 1.9 ± 0.1 MeV/c 2 (FWHM) ΔM for Θ + : 1.4 MeV/c 2 (FWMH) Production cross section of Σ + overall efficiency is examined with σ(σ + ). ε all = 0.25 Achieved enough good resolution. Yield is consistent with the estimation. 18

19 Missing Mass Spectrum The First Data at p p =1.92GeV/c data background (sim.) p(π-,k-) 90% C.L. upper limit cross section accepted in PRL, arxiv: [nucl-ex] no significant structure has been observed. upper limit is 0.26mb/sr (90%C.L.) cf. 2.9mb/sr (E522) 19

20 dσ/dω [Γ Θ /(1MeV)] [μb] dσ/dω [Γ Θ /(1MeV)] [μb] Decay width of Θ Since σ tot Γ Θ, upper limit of σ tot gives the upper limit of Γ Θ σ tot can be obtained from upper limit of dσ/dω calculated angular distribution U. L. of σ tot [μb/sr] J p = ½+ ½- PS PV σ tot theory [Γ Θ /(1MeV) μb/sr] J p = ½+ ½- PS PV PS,Fs PS,Fc PV,Fs PV,Fc (π,k),1/ cosθ PV,Fs PV,Fc PS,Fs PS,Fc (π,k),1/2- upper limit of Γ Θ 0.72 MeV for J=1/ MeV for J=1/ cosθ T. Hyodo et al., arxiv:

21 [Γ Θ /(1MeV)] [mb] Go to higher energy the current upper limit obtained from the 1 st data is close to the theoretical estimation assuming the Γ Θ =1. the cross section is expected to increase with energy. by 1.5~1.7 times at p π =2GeV/c concentrate on taking data at the maximum energy available at the K1.8. Theoretical calculations : PS: Oh et al., PRD69(04) Ko, Lee & Park, PLB611(05)87 PV: T. Hyodo, PRC72(05) PS Fs (p, ) J p =1/ PS Fc PV Fs PV Fc max. s at K sqrts [MeV] p lab =1.92GeV/c 21

22 Vertex-Z Analysis of 2 nd Data M 2 distribution p(π-,k-) at p π = 2 GeV/c # beam π = 8.7x10 10 vertex reconstruction & PID are well performed. p K p Σ production is studied in p(π +,K + ) at p π = 1.37 GeV/c Σ + is reconstructed successfully. dm 1.6MeV(FWHM) for Θ + Σ+ Missing Mass M = 1.186MeV dm = 2.0MeV N event = ~1400 consistent with 1 st data 22

23 Missing Mass of 2 nd data p(π-,k-) at p π = 2 GeV/c count rate is consistent with the estimation. The expected sensitivity ~0.3μb/sr M. Moritsu, 29 th. 23

24 Summary J-PARC E19 searches for Q + in p p K X reaction with mass resolution of 1.4MeV(FWHM) We have not seen any structure on the missing mass spectrum with the data taken at p p =1.92GeV/c. The upper limit is 0.26mb/sr. o The bump observed in the past experiment was not real. o Q < 0.71MeV (J=1/2 + ) 3.1MeV (J=1/2 ). Spectrometer performance after the earthquake is OK. The result of the new data is coming soon. 24

25 2009/10/ /11/4 K1.8 Exp. Group Nov th. Feb ~70 people From KEK, Kyoto U., Tohoko U., U.Tokyo, Nara WU, Osaka U., JAEA, UNM(USA), INFN(Italy), Seol N. U., ITEP, JINR 25