Measurement of the $b \bar b$ Production Cross Section in 920 GeV Fixed-Target Proton-Nucleus Collisions

TL;DR

This paper reports a measurement of the bottom quark-antiquark production cross section in 920 GeV proton-nucleus collisions using the HERA-B detector, employing decay vertex separation techniques for identification.

Contribution

It provides the first measurement of the b-bbar production cross section at this energy in fixed-target proton-nucleus collisions using vertex displacement methods.

Findings

Measured cross section: 32 nb/nucleon with uncertainties.

Used inclusive decay channels into J/psi for tagging.

Combined electron and muon decay channels analysis.

Abstract

Using the HERA-B detector, the b-bbar production cross section has been measured in 920 GeV proton collisions on carbon and titanium targets. The b-bbar production was tagged via inclusive bottom quark decays into J/psi, by exploiting the longitudinal separation of J/psi->ll decay vertices from the primary proton-nucleus interaction. Both $e^+e^-$ and $\mu^+\mu^-$ channels have been reconstructed and the combined analysis yields the cross section $\sigma(b \bar b) = 32 ^{+14}_{-12} (stat) ^{+6}_{-7} (sys) nb/nucleon$.