1. Izabella Zychor EPIPHANY, Krakow, January 6-8, 2005 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

2. Izabella Zychor 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 π 0 π 0 Λ COSY – a unique possibility to search for hyperons in hadron induced reactions

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

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

5. Izabella Zychor EPIPHANY, Krakow, January 6-8, 2005 5 3.65 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 ± )

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

7. Izabella Zychor EPIPHANY, Krakow, January 6-8, 2005 7 V. Koptev, I. Zychor, P. Kravchenko and M. Nekipelov, Annual Report 2002 ( IKP and Swierk )

8. Izabella Zychor EPIPHANY, Krakow, January 6-8, 2005 8

9. Izabella Zychor EPIPHANY, Krakow, January 6-8, 2005 9 EXPERIMENTAL RESULTS

10. Izabella Zychor EPIPHANY, Krakow, January 6-8, 2005 10 (i) pp pK + Y Y = (1385), (1405), (1520) (ii) non-resonant production pp NK + X, NK + π X, NK + π π X X = hyperon

11. Izabella Zychor EPIPHANY, Krakow, January 6-8, 2005 11 Comparison of Monte Carlo simulations and experimental data pp pK + Y and non-resonant production pp pK X

12. Izabella Zychor EPIPHANY, Krakow, January 6-8, 2005 12 (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 )

13. Izabella Zychor EPIPHANY, Krakow, January 6-8, 2005 13 RESULTS Y 0 *: M=1480 MeV/c 2, Γ=60 MeV/c 2 pp pK X

14. Izabella Zychor EPIPHANY, Krakow, January 6-8, 2005 14 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, 1970 1440 MeV/c 2 by H.Högaasen and P.Sorba, 1978 1495 MeV/c 2 by Y.Oh et al., Phys. Rev. D 69, 035208 (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 !

15. Izabella Zychor EPIPHANY, Krakow, January 6-8, 2005 15 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 +

16. Izabella Zychor EPIPHANY, Krakow, January 6-8, 2005 16 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