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Pentaquark Q + search experiment at J-PARC

Pentaquark Q + search experiment at J-PARC. M. Moritsu ( Kyoto University  RCNP, Osaka University ) f or the J-PARC E19 collaboration. Baryons2013 @ Glasgow, 2013/06/24. Contents. Introduction J-PARC E19 experiment Overview of the experiment New result of E19-2 nd run Summary.

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Pentaquark Q + search experiment at J-PARC

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  1. Pentaquark Q+ search experiment at J-PARC M. Moritsu ( Kyoto University  RCNP, Osaka University ) for the J-PARC E19 collaboration Baryons2013 @ Glasgow, 2013/06/24

  2. Contents • Introduction • J-PARC E19 experiment • Overview of the experiment • New result of E19-2nd run • Summary

  3. J-PARC E19 Collaboration

  4. Pentaquark search Pentaquark Q+ • Genuine exotic hadron (uuddsbar ) • M = ~1540 MeV/c2 (decay Q+ KN) Historical background • Q+ pentaquark was first predicted by Diakonov et al. in 1997. • SPring8/LEPS group reported the evidence for Q+ in 2003. • Dozen experimental groups published supporting evidence for the Q+, • followed by a number of experiments with no evidence. Situation is still controversial ...

  5. Physics Motivation • Distinctive feature of Q+ pentaquark • Need some mechanism to suppress decay. Narrow Width ( < a few MeV ) Diquark structure (Need quark rearrangement for KN decay) Meson-Baryon molecule R.Jaffe,F.Wilczek (2003) Useful tool to understand low energy QCD dynamics !!

  6. Our Approach ( J-PARC E19 ) • Pion induced reaction • Complementary to photo-production (LEPS/CLAS). • Expect sizable production cross section. => High statistics p- + p → K- + Q+ 2.6s Previous experiment • High resolution missing mass spectroscopy • K1.8 beam line & SKS = DM < 2 MeV (FWHM) KEK-PS E522 Miwa et al., PLB 635, 72. • DM ~ 13.4 MeV • (FWHM)

  7. Our Approach ( J-PARC E19 ) • Pion induced reaction • Complementary to photo-production (LEPS/CLAS). • Expect sizable production cross section. => High statistics p- + p → K- + Q+ • High resolution missing mass spectroscopy • K1.8 beam line & SKS = DM < 2 MeV (FWHM) Conclusive result by higher sensitivity !!

  8. Experimentalsetup J-PARC K1.8 Dedicated to the (p,K) reaction spectroscopy p- beam 1.92/2.00 GeV/c

  9. History of E19 • Shirotori et al., PRL109, 132002 (2012). • Q+ Peak was not observed. • We concluded that E522 bump was not the signal by 10 times higher sensitivity. This presentation

  10. Note on Q+ decay width 4 Theoretical calculations : T. Hyodo et al., PRC 72, 055202 (2005), PTP 128, 523 (2012). PV Fs 500MeV PV Fc 1800MeV Jp=1/2+, GQ+ = 1MeV s [mb] 2 • s-channel dominance • GQ∝ g2KNQ∝ s plab=2.0 GeV/c • Higher beam momentum provideshigher sensitivity. • 2.0 GeV/c • ( = Max. of K1.8 B.L.) • Even if no peak, stronger constraint on the Q+ decay width will be obtained. 0 1800 2000 2200 2400 2600 sqrt(s) [MeV] plab= 1.92 GeV/c

  11. Result of the E19-2nd run

  12. Example of analysis 1 Scattered particle M2 SKS spectrometer • SKS system : pK PID counters • Timing counter • Aerogel Cherenkov (K/p) : n=1.05 • Lucite Cherenkov (K/p) : n=1.49 Tracking • MWDCs : 3 mm pitch • DCs : 10 mm pitch, 2m×1m size p K p We can separate only K very clearly. Good momentum reconstruction and PID !! M2 [GeV2]

  13. Example of analysis 2 Vertex Reconstruction LH2 Target cell K p Vertex-Z f67.8 × 120 mm Vertex-(X vs Y) LH2 target Empty target (scaled) Beam Consistent with horizontally oblate beam shape. window window Target cell is clearly identified !!

  14. Consistency check with previous exp. S+ Missing Mass • p++ p → K+ + S+@ 1.37 GeV/c • Missing mass resolution: DMS = 1.92 MeV(FWHM) • Equivalent to the 1st run. Cf.) 1.86±0.08 MeV@ E19-1st Preliminary p+ + p → K+ + S+@ 1.37 GeV/c DMQ = 1.74 MeV(FWHM) E19-2nd Preliminary DM = 1.92 ±0.05 MeV S+

  15. Consistency check with previous exp. S+ Differential Cross Section p+ + p → K+ + S+@ 1.37 GeV/c • p++ p → K+ + S+@ 1.37 GeV/c • Missing mass resolution: DMS = 1.92 MeV(FWHM) • Equivalent to the 1st run. Cf.) 1.86±0.08 MeV@ E19-1st Preliminary DMQ = 1.74 MeV(FWHM) • Differential cross section • Almost consistent with 1st run and reference data. • Good understanding of efficiencies and acceptance. Consistency Check  OK

  16. Analysis Result of E19-2nd run An example of fitting result @ 1.535 GeV/c2 p- + p → K- + X@ pp = 2.0 GeV/c E19-2nd Preliminary Fitting results of each mass and Upper limit (90%C.L.) • No peak structure was observed. • Upper limit on differential cross section averaged from 2 to 15 deg: • < 0.28 mb/sr @ 1.50 – 1.57 GeV/c2

  17. Upper limit on decay width • Considering about theoretical uncertainty (coupling scheme and form factor), we chose the most conservative case as the upper limit. Upper Limit on GQ for JPQ gKNQ GQ∝ g2KNQ ∝ s T. Hyodo et al., PTP 128, 523 (2012). • 0.61 MeV for ½+ • 3.7 MeV for ½-

  18. Summary • J-PARC E19 is a pentaquark Q+search experiment with high statisticsand high resolution. • p- p → K-Q+ reaction • J-PARC K1.8 B.S. and SKS • New result of E19-2nd run was presented. • Consistency with the 1st run was checked.  O.K. • Q+ missing mass resolution of 1.74 MeV was evaluated. • No peak structure was observed in MM spectrum. • Upper limit for Q+ production cross section was obtained to be 0.28 mb/sr @ 1.50 – 1.57 GeV/c2 • This corresponds to upper limit on Q+ decay width of 0.61 and 3.7 MeV for JP = ½+ and ½-, respectively.

  19. Backups

  20. 1st run result of E19 Shirotori et al., PRL109, 132002 (2012). p- + p → K- + X @ 1.92 GeV/c • No prominent peak structure • Upper limit: < 0.26 mb/sr @ 1.51-1.55 GeV/c2 E19-1st data background (sim.) • s-channel dominance • GQ∝ g2KNQ∝ s • Upper limit of decay width • 0.72 MeV for ½+ • 3.1 MeV for ½-

  21. 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) Simulation with measuredcross section using angular distributions • f production : uniform (S-wave) • L(1520) : ∝ 1+cos2qcm(D-wave) O. I. Dahl et al . Phys. Rev. B 163, 1377 (1967). (Bubble chamber data)

  22. Cut condition : NpK = 1 2 < q< 15 deg Vertex-(X2+Y2) < 252 mm2 -60 < Vertex-Z < 60 mm 0.15 < m2 < 0.4 GeV2 c2 cut : Local tracking c2 < 20 (BcOutc2 < 10) SKS, K18 tracking c2 < 30

  23. Prev. Exp. Previous experiments at KEK-PS E522 : p- p → K-Q+ @ 1.92 GeV/c • E559 : K+ p → p+Q+@1.20 GeV/c K+-induced p--induced 2.6s 1.53 GeV K. Miwa et al., PLB 635, 72 (2006). K. Miwa et al., PRC 77, 045203 (2008). • Bump structure (2.6s) •  Not enough to claim the existence • Upper limit: s < 3.9 mb (90% C.L.) • No peak structure • Upper limit: s < 3.5 mb/sr(90% C.L.)

  24. Positive Results (~2005) LEPS DIANA CLAS-d SAPHIR 5.1 3.2 3.4 4.3 ITEP 3.6 CLAS-p 4.9 HERMES ZEUS 3.6 4~5 COSY-TOF SVD 4.7 4.4 [CAUTION] Significances ware recalculated by significance = S/√(S+B) or S/dS

  25. Positive Results (updated) LEPS DIANA 5.1 5.5 CLAS-d < 0.3 nb ITEP 3.6 CLAS-p 4.9 HERMES ZEUS 3.6 4~6 COSY-TOF < 0.15mb Some confirmed their evidence, but others did not... SVD [CAUTION] Significances ware recalculated by significance = S/√(S+B) or S/dS 5.8

  26. BES BELLE FOCUS HERA-B BABAR HyperCP CDF SPHINX Negative Results LEP _ PHENIX (Q-)

  27. J-PARC Hadron facility K1.8BR K1.8 T1 target Primary proton beam K1.1BR KL High-p

  28. 2009 Oct SKS Spectrometer SDC3 AC1 SDC4 AC2 SDC2 TOF SDC1 Target LC BC4 BH2 Q13 BC3 BC2 BC1 GC Q12 BH1 MS2 K1.8 Beam Spectrometer D4 Q11 Q10

  29. Recovery from the earthquake Rotation of SKS 2011 Sep. • Injection angle : 30  15 deg. • Higher-momentum acceptance. • For future experiments.

  30. Setup difference of 1st and 2nd run E19-1st run (2010) E19-2nd run (2012) 15 deg. injection 30 deg. injection

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