Measurement of K0S, Lambda, Antilambda production at HERA

TL;DR

This paper reports measurements of strange hadron production in electron-proton collisions at HERA, comparing results across different kinematic regions and with models, revealing general agreement but an unexpected baryon enhancement in photoproduction.

Contribution

First detailed measurement of $K^0_S$, $\Lambda$, and $ar{\Lambda}$ production at HERA across multiple kinematic regimes, including baryon-to-meson ratios and polarization.

Findings

Measurements generally agree with Monte Carlo models.

Results are consistent with $e^+ e^-$ collider data.

Observed baryon enhancement in photoproduction.

Abstract

The production of the neutral strange hadrons $K^{0}_{S}$, $\Lambda$ and $\bar{\Lambda}$ has been measured in $ep$ collisions at HERA using the ZEUS detector. Cross sections, baryon-to-meson ratios, relative yields of strange and charged light hadrons, $\Lambda$ ($\bar{\Lambda}$) asymmetry and polarization have been measured in three kinematic regions: $Q^2 > 25 \gev^2$; $5 < Q^2 < 25 \gev^2$; and in photoproduction ($Q^2 \simeq 0$). In photoproduction the presence of two hadronic jets, each with at least $5 \gev$ transverse energy, was required. The measurements agree in general with Monte Carlo models and are consistent with measurements made at $e^+ e^-$ colliders, except for an enhancement of baryon relative to meson production in photoproduction.