Strangeness Production in Deep-Inelastic Positron-Proton Scattering at HERA

TL;DR

This paper reports measurements of strange particle production in deep-inelastic positron-proton scattering at HERA, analyzing spectra, multiplicities, and mechanisms, including limits on instanton-induced processes, to understand strangeness production at low Bjorken-x.

Contribution

It provides detailed measurements of $K^0$ and $\\Lambda$ production in DIS and compares them with electron-positron results, offering insights into strangeness production mechanisms and limits on instanton effects.

Findings

Mean $K^0$ and $\Lambda$ multiplicities increase logarithmically with energy $W$.

Strangeness production levels are similar in diffractive and non-diffractive DIS.

Upper limit of 0.9 nb set on instanton-induced event cross-section.

Abstract

Measurements are presented of $K^0$ meson and $\Lambda$ baryon production in deep-inelastic positron-proton scattering (DIS) in the kinematic range $10 < Q^2 < 70 $GeV$^2$ and $10^{-4} < x < 10^{-2}$. The measurements, obtained using the H1 detector at the HERA collider, are discussed in the light of possible mechanisms for increased strangeness production at low Bjorken-$x$. Comparisons of the $x_F$ spectra, where $x_F$ is the fractional longitudinal momentum in the hadronic centre-of-mass frame, with results from electron-positron annihilation are made. The $x_F$ spectra and the $K^0$ ``seagull'' plot are compared with previous DIS results. The mean $K^0$ and $\Lambda$ multiplicities are studied as a function of the centre-of-mass energy $W$ and are observed to be consistent with a logarithmic increase with $W$ when compared with previous measurements. A comparison of the levels of strangeness production in diffractive and non-diffractive DIS is made. An upper limit of $0.9 $nb, at the 95% confidence level, is placed on the cross-section for QCD instanton induced events.