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Search for Q + via K + p -> p + X reaction with high-resolution spectrometer system

Search for Q + via K + p -> p + X reaction with high-resolution spectrometer system. Kyoto University S. Dairaku for E559 collaboration. E559 collaboration. Gifu U. T. Kameyama, K. Nakazawa, T. Watanabe KEK S. Ishimoto, T. Nagae, H, Noumi, Y. Sato, S. Sawada,

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Search for Q + via K + p -> p + X reaction with high-resolution spectrometer system

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  1. Search for Q+ via K+p ->p+X reaction with high-resolution spectrometer system Kyoto University S. Dairaku for E559 collaboration

  2. E559 collaboration Gifu U. T. Kameyama, K. Nakazawa, T. Watanabe KEK S. Ishimoto, T. Nagae, H, Noumi, Y. Sato, S. Sawada, M. Sekimoto, S. Suzuki, H. Takahashi, T. Takahashi, N. Tanaka, A. Toyoda Kyoto U. S. Dairaku, H. Funahashi, K. Imai*, K. Miwa, K. Shoji, M. Hayata, M. Miyabe, M. Niiyama, N. Saito, Y. Seki Ohio U. K. Hicks, R. Zavislak Osaka U. S. Ajimura Osaka EC U. T. Fukuda RCNP T. Nakano, M. Yosoi RIKEN M. Naruki, K. Tanida Tohoku U. S. Kinoshita, T. Koike, Y. Ma, Y. Miura, K. Shirotori, H. Tamura U. Paris-Sud J. Arvieux U. Tokyo H. Fujioka, T. Maruta, D. Nakajima, T. N. Takahashi

  3. Purpose • Search for Q+ Pentaquark ( E559 at KEK-PS K6) • if Q+ exists, G< 1 MeV/c2 (M=1530 - 1540 MeV/c2) • High Resolution spectrometer SKS & K6beamline ⇒resolution ： 2.4 MeV/c2 (FWHM) • High statistics • Hadronic reaction K+p -> p+X • 1.2 GeV/c K+ beam and liquid H2 target • Determination of decay angle distribution • Large solid angle Drift Chamber & Range Counter downstream of target • Spin and Parity

  4. 1.6 T Solid angle 0 - 60 deg π+(0.5 - 0.6 GeV/c) p+ K+ For π+veto mass2(GeV/c2)2 p+ Setup SKS K+ (1.2GeV/c)

  5. Data set RUN1 ( 2005/5/24 - 2005/7/1 ) H(K+,p+) run @1.2GeV/c for + K+ yield : 2.79x109 Empty target run @1.2GeV/c for B.G. H(p+,K+) run @1.1GeV/c for S+ RUN2 ( 2005/12/13 - 2005/12/28 ) H(K+,p+) run @1.2GeV/c for + K+ yield: 2.09x109 Empty target run @1.2GeV/c for B.G. H(p+,K+) run @1.1GeV/c for S+

  6. Resolution for + and  M=1189.31 ± 0.03 MeV/c2 G=2.03 ± 0.06 MeV/c2 1st run Resolution K6 : p/p = 0.047% (FWHM) SKS : p/p = 0.43% (FWHM) (simulation) for S+1.98 MeV/c2 (FWHM) This is consistent with real data Mass(GeV/c2) (simulation) for 2.4 MeV/c2 (FWHM) 2nd run M=1189.33±0.03 MeV/c2 G=1.94±0.07 MeV/c2 Missing mass value 1st run is consistent with 2nd run Mass(GeV/c2)

  7. Vertex distribution (before B.G. cut) 1st run 2nd run (K+, p+) (K+, p+) (p+, p+) (p+, p+) vertex z(mm) vertex z(mm) (K+, p+) reaction : large background from K+ decay

  8. π+ K+ K+ decay event vertex p+( to SKS ) K+ K+ SDC1 analysis cut K+p reaction event 98.0% of K+ decay events are suppressed (simulation) 70.1% of Q+ production events remain (simulation --- assume isotropic angular distribution) Even charged & Large scattered angle p+( to SKS ) Suppression of K+ decay events(SDC1 analysis cut) π+veto Aerogel Target SKS Beam line chamber SDC2 SDC1 RC drift chamber

  9. vertex distribution (after B.G. cut) 2nd run 1st run vertex z(mm) vertex z(mm) 16900 event (-30<z<100) 11900 event (-40<z<85)

  10. Assumption Sum of 1st and 2nd runs 1530MeV/c2 s=50mb isotropic distribution Expected peak under assumption Missing Mass (pX) Preliminary

  11. Missing Mass (pX) Preliminary 170 ( 90% C.L. upper limit)

  12. 90% C.L. upper limit 90% C.L. upper limit Upper limit Preliminary

  13. G=1MeV gK*NQ= ＋gKNQ gK*NQ= －gKNQ gK*NQ= 0 Cross section of H(K+,π+) reaction Y. Oh et al. Phys. Rev. D 69, 074016 L=1.2GeV W/O F.F. √s=1.89GeV ( E559 exp. )

  14. G=1MeV gK*NQ= ＋gKNQ gK*NQ= －gKNQ gK*NQ= 0 Cross section of H(K+,π+) reaction Y. Oh et al. Phys. Rev. D 69, 074016 Preliminary E559 exp. 90% C.L. upper limit L=1.2GeV W/O F.F.

  15. Summary • Search for Q+ via H(K+, p+) reaction at KEK-PS K6 beamline • K+ beam yield 4.88x109 reaction event 28800 (after SDC1 cut) • No significant peak (1520 － 1560 MeV/c2) • cross section 7.0mb, 1.9mb/sr 90% C. L. upper limit(assume angular distribution) Preliminary much smallerthantheoretical value under K* exchange (calculated by Y.Oh )

  16. END

  17. (K+, p+) Vertex collect near SDC1 (p+, p+) peak at SDC1 position SDC1 RC SDC2 20cm Target K+ beam 20cm Decay SKS Gap

  18. Background in H(K+,p+)reaction

  19. π+ Angle cut study n Selection of 2 select kinematics? Target K+ 1 SKS 2 K+ 1 (degree) Simulation No correlation between () and (K+, p) 2 (degree)

  20. SDC1 analysis • If we assume that Q+ decay is isotropic in center of mass frame, accepted ratio of each decay mode • K+n : 0.637 • K0Sp : 0.729 • K0Lp : 0.804 • Weighted mean with decay ratio ( 0.5:0.25:0.250.701 )→0.701

  21. Q2 of reactions CLAS E522 (p-,K-) 1.9GeV/c Angle [degree] E559 (K+,p+) 1.2GeV/c LEPS Q2=q2-w2 [GeV2]

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