Measurement of Beauty Production at HERA Using Events with Muons and Jets

TL;DR

This work reports a comprehensive measurement of open beauty production in $ep$ collisions at HERA by the H1 collaboration, spanning photoproduction and DIS. Beauty identification relies on two observables, the muon’s transverse momentum relative to a jet and the muon’s impact parameter, to disentangle $b$-quark events from charm and light-flavor backgrounds. The results are compared to NLO QCD calculations in the massive scheme and to LO Monte Carlo generators, with data generally exceeding the NLO predictions, particularly at low $p_t$ and in certain kinematic regions, and showing consistency in shape with the theory. The analysis confirms a non-negligible role for resolved-photon processes in photoproduction and provides a benchmark for heavy-flavor production in $ep$ collisions, aligning with ZEUS and prior H1 measurements.

Abstract

A measurement of the beauty production cross section in ep collisions at a centre-of-mass energy of 319 GeV is presented. The data were collected with the H1 detector at the HERA collider in the years 1999-2000. Events are selected by requiring the presence of jets and muons in the final state. Both the long lifetime and the large mass of b-flavoured hadrons are exploited to identify events containing beauty quarks. Differential cross sections are measured in photoproduction, with photon virtualities Q^2 < 1 GeV^2, and in deep inelastic scattering, where 2 < Q^2 < 100 GeV^2. The results are compared with perturbative QCD calculations to leading and next-to-leading order. The predictions are found to be somewhat lower than the data.

Figures (11)

• Figure 1: Beauty production processes in leading order pQCD.
• Figure 2: Distributions in photoproduction of a) the muon transverse momentum $p_t^{\mu}$, b) the pseudo-rapidity of the muon $\eta^{\mu}$, c) and d) the transverse momenta $p_t^{jet_{1(2)}}$ of the highest and the second-highest $p_t$ jets, respectively and e) the observable $x_{\gamma}^{obs}$. Included in the figure are the estimated contributions of events arising from $b$ quarks (dashed line), $c$ quarks (dotted line) and light quarks (dash-dotted line). The shapes of the distributions from the different sources are taken from the PYTHIA Monte Carlo simulation and their relative fractions are determined from a fit to the two-dimensional data distribution of $\,p_t^{rel}\,$ and $\delta\;$ (see text).
• Figure 3: Distributions in electroproduction of a) the photon virtuality $Q^2$, b) the inelasticity $y$, c) Bjorken x, d) the muon transverse momentum and e) the transverse momentum $p^{Breit}_{t,jet}$ of the selected jet in the Breit frame. Included in the figure are the estimated contributions of events arising from $b$ quarks (dashed line), $c$ quarks (dotted line) and light quarks (dash-dotted line). The shapes of the distributions from the different sources are taken from the RAPGAP Monte Carlo simulation and their relative fractions are determined from a fit to the two-dimensional data distribution of $\,p_t^{rel}\,$ and $\delta\;$ (see text).
• Figure 4: Distributions in photoproduction of a) the impact parameter $\delta\;$ of the muon track and b) the transverse muon momentum $\,p_t^{rel}\,$ relative to the axis of the associated jet. Included in the figure are the estimated contributions of events arising from $b$ quarks (dashed line), $c$ quarks (dotted line) and the light quarks (dash-dotted line). The shapes of the distributions of the different sources are taken from the PYTHIA Monte Carlo simulation and their relative fractions are determined from a fit to the two-dimensional data distribution of $\,p_t^{rel}\,$ and $\delta\;$ (see text).
• Figure 5: Distributions in electroproduction of a) the impact parameter $\delta\;$ of the muon track and b) the transverse muon momentum $\,p_t^{rel}\,$ relative to the axis of the associated jet. Included in the figure are the estimated contributions of events arising from $b$ quarks (dashed line), $c$ quarks (dotted line) and the light quarks (dash-dotted line). The shapes of the distributions of the different sources are taken from the RAPGAP Monte Carlo simulation and their relative fractions are determined from a fit to the two-dimensional data distribution of $\,p_t^{rel}\,$ and $\delta\;$ (see text).