K0S and L production at ZEUS Alexander A. Savin University of Wisconsin On Behalf of the ZEUS Collaboration DIS 2006, Tsukuba, Japan

Outline 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

Kinematic Variables e+(-) p Photon virtuality inelasticity (820) Photon virtuality inelasticity Bjorken scaling variable

Event and Particle Selection ZEUS 1996-2000 data 121 pb-1 DIS: 5<Q2<25 or Q2>25 GeV2; 0.02<y<0.95 PHP: Q2<1 GeV2; 0.2<y<0.85 2 jets with ETjet>5 GeV Particle selection: - Secondary vertex ; -

Strange production mechanism - strangeness suppression factor

K0S DIS cross sections ARIADNE with 0.3 describes data well, 0.2 less satisfactory LEPTO does not describe the data

L DIS cross sections ARIADNE with 0.3 describes data well, 0.2 less satisfactory LEPTO does not describe the data

PHP cross sections PYTHIA describes the data well, xgOBS is too flat

Baryon-antibaryon asymmetry - small or no asymmetry ; - “gluon junction mechanism”, 3.5% positive, RHIC

Baryon to meson ratio Low Q2 region is better described by the ARIADNE

Baryon to meson ratio - ARIADNE reasonably describes the data; - the ratios are similar to those from ee and pp.

Photoproduction with 2 jets

Fireball type of event

Fireball sample selection Total transverse energy Highest transverse energy jet

Baryon to meson ratio, PHP Similar to DIS PYTHIA does not describe fireball enriched sample

Strange to light hadrons ratio Nch – number of charged pions, charged kaons, protons and antiprotons Similar to ee ARIADNE with 0.22 describes data well

Strange to light hadrons ratio PYTHIA describes data well (instanton contribution?)

Polarization No polarization Polarization in scattering due to the strong interaction = 0.642 - decay asymmetry parameter q - angle between the proton(antiproton) direction and the polarization axis No polarization

Summary Measurements of K0S, L’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