Izabella Zychor EPIPHANY, Krakow, January 6-8, 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

Izabella Zychor EPIPHANY, Krakow, January 6-8, 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 π 0 π 0 Λ COSY – a unique possibility to search for hyperons in hadron induced reactions

Izabella Zychor EPIPHANY, Krakow, January 6-8, COoler SYnchrotron (Jűlich, Germany) protons and deuterons polarized and unpolarized p beam = 0.3 – 3.7 GeV/c

Izabella Zychor EPIPHANY, Krakow, January 6-8, ANKE: magnetic spectrometer at internal target position of COSY

Izabella Zychor EPIPHANY, Krakow, January 6-8, GeV/c proton beam Y hyperon mass < 1540 MeV/c 2 two final states: Y 0* π + X - and Y 0* π - X + three-particle coincidences (pK + π ± )

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

Izabella Zychor EPIPHANY, Krakow, January 6-8, V. Koptev, I. Zychor, P. Kravchenko and M. Nekipelov, Annual Report 2002 ( IKP and Swierk )

Izabella Zychor EPIPHANY, Krakow, January 6-8,

Izabella Zychor EPIPHANY, Krakow, January 6-8, EXPERIMENTAL RESULTS

Izabella Zychor EPIPHANY, Krakow, January 6-8, (i) pp pK + Y Y = (1385), (1405), (1520) (ii) non-resonant production pp NK + X, NK + π X, NK + π π X X = hyperon

Izabella Zychor EPIPHANY, Krakow, January 6-8, Comparison of Monte Carlo simulations and experimental data pp pK + Y and non-resonant production pp pK X

Izabella Zychor EPIPHANY, Krakow, January 6-8, (i) pp pK + Y Y = (1385), (1405), (1520) (ii) pp NK + X, NK + π X, NK + π π X X = hyperon (iii) additional contribution pp pK + Y 0* ( M, Γ )

Izabella Zychor EPIPHANY, Krakow, January 6-8, RESULTS Y 0 *: M=1480 MeV/c 2, Γ=60 MeV/c 2 pp pK X

Izabella Zychor EPIPHANY, Krakow, January 6-8, WHAT IS Y 0 *(1480) ? Λ or Σ 0 resonance ? 3-valence quark models: no room for Y 0 * (?) no additional excited Λ or Σ resonances 1600 MeV/c 2 ( e.g. S.Capstick and N.Isgur, U. Loehring et al. ) 5-quark configurations 1480 MeV/c 2 by Ya.I.Azimov, MeV/c 2 by H.Högaasen and P.Sorba, MeV/c 2 by Y.Oh et al., Phys. Rev. D 69, (2004) 1446 MeV/c 2 and width of 343 MeV/c 2 in kaon-nucleon quasibound state C.Garcia, M.Lutz and J.Nieves, Phys. Lett. B 582, 49 (2004) no clear theoretical picture !

Izabella Zychor EPIPHANY, Krakow, January 6-8, Y 0* mass: ( 1480 ± 15 ) MeV/c 2 Y 0* width: ( 60 ± 15 ) MeV/c 2 cross section of a few hundred nanobarns consistent for both final states statistical significance at the 4.8 σ level Y 0 * non-3 quark candidate ? Summary Y 0* observed in pp collisions in two final states: Y 0* π + X - and Y 0* π - X +

Izabella Zychor EPIPHANY, Krakow, January 6-8, OUTLOOK measurement at higher beam momentum 3.70 GeV/c charged Y* at ANKE with deuterium target Y* decays with photons in final states with WASA at COSY