1. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 1 K 0 S and  production at ZEUS Alexander A. Savin University of Wisconsin On Behalf of the ZEUS Collaboration DIS 2006, Tsukuba, Japan

2. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 2 OutlineOutline -Strange mesons and baryons cross sections ; -Baryon-antibaryon asymmetry ; -Baryon to meson ratio ; -Strange to light mesons ratio ; -Polarization. In the wide kinematic range of ep interaction at HERA

3. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 3 Kinematic Variables Bjorken scaling variable inelasticity Photon virtuality e +(-) p (820)

4. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 4 Particle selection: - Secondary vertex ; - Event and Particle Selection ZEUS 1996-2000 data 121 pb -1 DIS: 5 25 GeV 2 ; 0.02<y<0.95 PHP: Q 2 <1 GeV 2 ; 0.2<y<0.85 2 jets with E T jet >5 GeV

5. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 5 Strange production mechanism - strangeness suppression factor

6. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 6 K 0 S DIS cross sections ARIADNE with 0.3 describes data well, 0.2 less satisfactory LEPTO does not describe the data

7. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 7  DIS cross sections ARIADNE with 0.3 describes data well, 0.2 less satisfactory LEPTO does not describe the data

8. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 8 PHP cross sections PYTHIA describes the data well, x  OBS is too flat

9. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 9 Baryon-antibaryon asymmetry - small or no asymmetry ; - “gluon junction mechanism”, 3.5% positive, RHIC

10. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 10 Baryon to meson ratio Low Q 2 region is better described by the ARIADNE

11. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 11 Baryon to meson ratio - ARIADNE reasonably describes the data; - the ratios are similar to those from ee and pp.

12. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 12 Photoproduction with 2 jets

13. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 13 Fireball type of event

14. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 14 Fireball sample selection Total transverse energy Highest transverse energy jet

15. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 15 Baryon to meson ratio, PHP Similar to DIS PYTHIA does not describe fireball enriched sample

16. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 16 Strange to light hadrons ratio N ch – number of charged pions, charged kaons, protons and antiprotons Similar to ee ARIADNE with 0.22 describes data well

17. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 17 Strange to light hadrons ratio PYTHIA describes data well (instanton contribution?)

18. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 18 PolarizationPolarization Polarization in scattering due to the strong interaction  decay asymmetry parameter  angle between the proton(antiproton) direction and the polarization axis No polarization

19. K 0 S and  production at ZEUS, A. Savin, University of Wisconsin DIS 2006, April 22, 2006 - 19 SummarySummary Measurements of K 0 S,  ’s production have been made at ZEUS using 121 pb -1 int.luminosity -no baryon-antibaryon asymmetry is observed ; -no transverse polarization is observed ; -ARIADNE and PYTHIA describe data well. For the strange to light meson ratio ARIADNE requires strangeness suppression factor 0.22, rather than 0.3, which used to describe other distributions ; -the ratio of baryons to mesons is large in the PHP resolved region and in the fireball PHP region, is much larger than in ee and is not described by PYTHIA