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Light excited hyperon Production on a proton target at CLAS

Light excited hyperon Production on a proton target at CLAS. Lei Guo for CLAS Collaboration Thomas Jefferson National Accelerator Facility, Newport News, VA. Motivation Search for Missing hyperons such as S (1480) Accurate S(1385) Xsection measurement

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Light excited hyperon Production on a proton target at CLAS

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  1. Light excited hyperon Production on a proton target at CLAS Lei Guo for CLAS Collaboration Thomas Jefferson National Accelerator Facility, Newport News, VA • Motivation • Search for Missing hyperons such as S(1480) • Accurate S(1385) Xsection measurement • High stattistics CLAS data:~70/pb-1, E0=4 GeV • Production mechanism? • gp→K+ L(p0) analysis • gp→K+ p-/+(S-/+) analysis:S(1480)Sp? • L(1520) Xsection measurement Lei Guo, D. P. Weygand NSTAR05, FSU

  2. Motivation 1: measurement of S(1385) differential cross section Accurate Measurent of ds/dt needed to isolate the double kaon component 1/(mK2 – t)2 Information useful in constraining KN dynamics at subthreshold energies M. Lutz, M. Soyeur, Nucl.Phys.A748:499 (2005) Lei Guo, D. P. Weygand NSTAR05, FSU

  3. Motivation 2: Is there a S(1480) state? L polarization : M2(Lp) p+p K+ p+ L M2(Lp) ??? JP ½ -1 Octet member? Y. Azimov, Phy. Rev. C68(2003) Y. Pan et al. Phys. Rev. D 2 (1970) Lei Guo, D. P. Weygand NSTAR05, FSU

  4. ZEUS result on Q+ Is there a S(1480)? hep-ex/0403051 S(1480)? Q(1540)? Lei Guo, D. P. Weygand NSTAR05, FSU

  5. Bremsstrahlung tagged photon facility, photon energy resolution ~0.2% (New Tagger Energy Calibration) CEBAF Large Acceptance Spectrometer@JLAB 6 Superconducting toroidal coils Electromagnetic calorimeters Beam line and the target Drift chambers TOF counters Cherenkov counters Tagger CLAS Detector Lei Guo, D. P. Weygand NSTAR05, FSU

  6. gp→K+ L(p0) analysisEvent seleciton MM2(K+L) M(pp-) p0 L gp0 h? pp Event selection: Timing cuts and missing momentum cuts at least one photon detected Lei Guo, D. P. Weygand NSTAR05, FSU

  7. gp→K+ L(p0) analysisBasic spectra S0(1385) K* K*+ K*L/ KS(1385)interference? Need quantified study Lei Guo, D. P. Weygand NSTAR05, FSU

  8. Background: gp→K+ L*, L*S0p0, S0(gL) p0side bankd events p0events MM(K+) MM(K+) Bump around 1500MeV due to L(1520) bckground Lei Guo, D. P. Weygand NSTAR05, FSU

  9. g K+ p0 K- p S(1385) L gp→K+ L(p0) analysisS(1385) Xsection ds/dt(gK+) Eg :1.7GeV) Eg :1.8GeV) Eg :2.5GeV) Eg :2.6GeV) preliminary Acceptance at low t region an issue Simulation t slope tuned to the data tslope (GeV/c2)-2 Eg (GeV) Lei Guo, D. P. Weygand NSTAR05, FSU

  10. gp→K+ L(p0) analysisS(1385) Xsection ds /dcos*(qK+ ) s(mb) Eg :2.2GeV) Eg :3.6GeV) preliminary Eg (GeV) Results consistent with scare old data Extrapolation for s(total) an issue Lei Guo, D. P. Weygand NSTAR05, FSU

  11. gp→K+ p-p+(n) analysis Selecting S+ Remove S- events M(np+) S- M(np-) S(1385) L(1405) M(S+p-) M(S+p-) L(1520) Small bump around 1.48GeV appears when S- events removed Lei Guo, D. P. Weygand NSTAR05, FSU

  12. gp→K+ p-/+(S-/+) analysis M2(S+p-) M2(S-p+) M2(p+p-) Bumps created by kinematics: Removing Ks0 and S Lei Guo, D. P. Weygand NSTAR05, FSU

  13. g K+ K0 K- p L(1520) n Extracting L(1520) Xsection preliminary • Three Groups worked independently • Different Particle Identification Schemes used • Cross section of L(1520) results consistent with SAPHIR • Errors ~ 30%, mostly due to statistics - Lei Guo, D. P. Weygand NSTAR05, FSU

  14. Summary • Multiple channels analyzed in search for S(1480) • No obvious signal observed in Sp orLp decay • Fake structure could be created by reflection or kinematical cuts • Preliminary results of S0(1385) Xsection (Eg=1.6~3.8 GeV) obtained • Preliminary results of L(1520) (Eg=1.9~3.8 GeV) Xsection • K*+L/K+L ratio to be determined, theoretical help needed • Systematic study in progress Lei Guo, D. P. Weygand NSTAR05, FSU

  15. gp→K+ L(p0) analysis S0events removed by Pmissing cut Missing momentum cuts for selecting p0 Lei Guo, D. P. Weygand NSTAR05, FSU

  16. gp→K+ L(p0) analysis MM2(LK+) MM2(LK+) after Pmiss cut Before Pmiss cut p0 Effects of missing momentum cuts Lei Guo, D. P. Weygand NSTAR05, FSU

  17. gp→K+ L(p0) analysis Bump around 1.5GeV shifts with beam energy /w Lei Guo, D. P. Weygand NSTAR05, FSU

  18. gp→K+ L(p0) analysisS0(1385) yield extraction Eg = 2.5GeV M(Lp0 ) Lei Guo, D. P. Weygand NSTAR05, FSU

  19. gp→K+ p+(S-) analysis S+ S- Bump? around 1.48GeV when S+ events removed Lei Guo, D. P. Weygand NSTAR05, FSU

  20. gp→K0 p+ (L) analysis (40% g11 statistics) Events dominated by K*+ events and S+ (1385) No S+ (1480) observed (50% background) Lei Guo, D. P. Weygand NSTAR05, FSU

  21. gp→K+ p- p+ (L) analysis5% g11 statistics No obvious S(1480) in Lp spectrawith high Background Lei Guo, D. P. Weygand NSTAR05, FSU

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