Improved Measurement of the b-bbar Production Cross Section in 920 GeV Fixed-Target Proton-Nucleus Collisions

TL;DR

This paper reports a new measurement of the b-bbar production cross section in 920 GeV proton-nucleus collisions, using inclusive J/psi decays to identify bottom quark events, providing a more precise estimate of bottom production rates.

Contribution

The study introduces a novel method to measure b-bbar production cross section via inclusive J/psi decays with vertex separation, improving accuracy over previous measurements.

Findings

Measured b-bbar cross section: 14.9 ± 2.2 (stat) ± 2.4 (sys) nb/nucleon.

Determined the ratio of b-bbar to prompt J/psi production: 0.032 ± 0.005 (stat) ± 0.004 (sys).

Analyzed data in the x_f range -0.35 to 0.15.

Abstract

A new measurement of the b-bbar production cross section in 920 GeV proton-nucleus collisions is presented by the HERA-B collaboration. The b-bbar production is tagged via inclusive bottom quark decays into J/psi mesons, by exploiting the longitudinal separation of J/psi->ll decay vertices from the primary proton-nucleus interaction point. Both e+e- and mu+mu- channels are reconstructed, for a total of 83 +- 12 inclusive b->J/psi X events found. The combined analysis yields a b-bbar to prompt J/psi cross section ratio of ${\frac{{\Delta\sigma(bbbar)}}{{\Delta\sigma_{\jpsi}}}} = 0.032\pm 0.005 \stat \pm 0.004 \sys$ measured in the x_f acceptance (-0.35 <x_f <0.15), extrapolated to $\sigma(bbbar) = 14.9 \pm 2.2 \stat \pm 2.4 \sys $ nb/nucleon in the total phase space.