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Hyperon production in pp collisions with ANKE at COSY

Hyperon production in pp collisions with ANKE at COSY. I. Zychor ( IPJ Świerk ) for the ANKE Collaboration. FZ Jülich, University: Erlangen, Giessen, Köln, Münster, FZ Rossendorf IPJ Świerk, UJ Cracow, INP Cracow PNPI Gatchina, JINR Dubna, Moscow : ITEP, INR, LPI, State University

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Hyperon production in pp collisions with ANKE at COSY

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  1. Hyperon production in pp collisions with ANKE at COSY I. Zychor ( IPJ Świerk ) for the ANKE Collaboration FZ Jülich, University: Erlangen, Giessen, Köln, Münster, FZ Rossendorf IPJ Świerk, UJ Cracow, INP Cracow PNPI Gatchina, JINR Dubna, Moscow : ITEP, INR, LPI, State University University Tbilisi University College London EPIPHANY, Krakow, January 6-8, 2005

  2. MOTIVATION • new results in hadron spectroscopy • e.g. Σ(1480) • 1-star “bump” in PDG • ZEUS: an indication in the invariant mass • Crystal Ball: not observed in K -pπ0π0Λ • COSY – a unique possibility to search for hyperons in hadron induced reactions EPIPHANY, Krakow, January 6-8, 2005

  3. COoler SYnchrotron (Jűlich, Germany) • protons and deuterons • polarized and unpolarized • pbeam = 0.3 – 3.7 GeV/c EPIPHANY, Krakow, January 6-8, 2005

  4. ANKE: magnetic spectrometer at internal target position of COSY EPIPHANY, Krakow, January 6-8, 2005

  5. 3.65 GeV/c proton beam • Y hyperon mass < 1540 MeV/c2 • two final states: Y0*π +X -and Y0*  π-X + • three-particle coincidences (pK +π ±) EPIPHANY, Krakow, January 6-8, 2005

  6. CHARGED PARTICLE IDENTIFICATION FORWARD GOING PARTICLES • time-of-flight : in scintillators • delayed signals from stopped K+ : in telescopes • momentum reconstruction in MWPCs EPIPHANY, Krakow, January 6-8, 2005

  7. EPIPHANY, Krakow, January 6-8, 2005

  8. EXPERIMENTAL RESULTS EPIPHANY, Krakow, January 6-8, 2005

  9. (i) pp  pK+YY = S(1385), L(1405), L(1520)(ii) non-resonant productionpp  NK+X, NK+ πX, NK+ ππXX = hyperon EPIPHANY, Krakow, January 6-8, 2005

  10. Comparison of Monte Carlo simulations and experimental datapp  pK+Yandnon-resonant production pp  pK+p+X- pp  pK+p-X+ EPIPHANY, Krakow, January 6-8, 2005

  11. (i) pp  pK+ YY = S(1385), L(1405), L(1520)(ii) pp  NK+X, NK+ πX, NK+ ππX X = hyperon(iii) additional contributionpp  pK+ Y0*(M, Γ ) EPIPHANY, Krakow, January 6-8, 2005

  12. RESULTS Y0*: M=1480 MeV/c2, Γ=60 MeV/c2 pp  pK+p+X- pp  pK+p-X+ EPIPHANY, Krakow, January 6-8, 2005

  13. WHAT IS Y0*(1480) ? • Λ or Σ0 resonance ? • 3-valence quark models: no room for Y0* (?) no additional excited Λ or Σ resonances ≤1600 MeV/c2 ( e.g. S.Capstick and N.Isgur, U. Loehring et al. ) • 5-quark configurations • 1480 MeV/c2 by Ya.I.Azimov, 1970 • 1440 MeV/c2 by H.Högaasen and P.Sorba, 1978 • 1495 MeV/c2 by Y.Oh et al., Phys. Rev. D 69, 035208 (2004) • 1446 MeV/c2 and width of 343 MeV/c2 in kaon-nucleon quasibound state C.Garcia, M.Lutz and J.Nieves, Phys. Lett. B 582, 49 (2004) no clear theoretical picture ! EPIPHANY, Krakow, January 6-8, 2005

  14. Summary • Y0* observed in pp collisions in two final states: Y0*π+X -and Y0*  π-X+ • Y0* non-3 quark candidate ? • Y0* mass: ( 1480 ± 15 ) MeV/c2 • Y0* width: ( 60 ± 15 ) MeV/c2 • cross section of a few hundred nanobarns consistent for both final states • statistical significance at the 4.8 σlevel EPIPHANY, Krakow, January 6-8, 2005

  15. OUTLOOK • measurement at higher beam momentum 3.70 GeV/c • chargedY* at ANKE with deuterium target • Y* decays with photons in final states with WASA at COSY EPIPHANY, Krakow, January 6-8, 2005

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