Measurement of the b-hadron production cross section using decays to D*muX final states in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

TL;DR

This ATLAS study measures b-hadron production in pp collisions at sqrt(s)=7 TeV using 3.3 pb^{-1} of data, via partial reconstruction of the final state D^{*}μX. Differential cross sections for D^{*}μX are extracted in p_T and η and unfolded to obtain corresponding b-hadron distributions, with an integrated cross section for p_T(B_hadron)>9 GeV of about 32.7 μb in the fiducial region. The analysis employs Bayesian unfolding, MC-based efficiency and acceptance corrections, and NLO QCD predictions (Powheg+Pythia as default) for comparison and extrapolation to the full phase space, where the total b-hadron cross section is around 360 μb. The results tend to lie above NLO predictions but are compatible within uncertainties, illustrating the ongoing tension between data and theory and providing important benchmarks at LHC energies.

Abstract

The b-hadron production cross section is measured with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV, using 3.3 pb^-1 of integrated luminosity, collected during the 2010 LHC run. The b-hadrons are selected by partially reconstructing D*muX final states. Differential cross sections are measured as functions of the transverse momentum and pseudorapidity. The measured production cross section for a b-hadron with pT>9 GeV and |eta|<2.5 is 32.7 pm 0.8 (stat) ^{+4.5}_{-6.8} (syst) ub, higher than the next-to-leading-order QCD predictions but consistent within the experimental and theoretical uncertainties.

Figures (3)

• Figure 1: (a) Distribution of the mass difference $\Delta m$ for $\dstaro\mu$ combinations of opposite charge (points) and same charge (dashed line). The solid line shows the result of the fit described in the text. (b) Distribution of the opposite charge $\dstaro\mu$ invariant mass, for mass combinations within $\pm3\sigma$ of the $\Delta m$ peak, without applying the invariant mass cut described in the text. The measured distribution is compared with the MC simulation, including the contribution of different sources of signal. The hashed bands show the MC statistical uncertainty.
• Figure 2: Differential cross section for $\dsmucross X$ production as a function of (a) $\pT$ and (b) $|\eta|$ of the $b$-hadron, in the fiducial kinematical region $\pT(\dstarp)>4.5\GeV, \pT(\mu^-)>6\GeV, |\eta(\dstarp)|<2.5$ and $|\eta(\mu^-)|<2.4$. The measurement is compared with the theoretical predictions, as described in the text. The inner error bars of the data points are statistical uncertainties, the outer are statistical+total systematic uncertainties.
• Figure 3: Differential cross section for $\Bhadrn$ production as a function of (a) $\pT$ and (b) $|\eta|$ of the $b$-hadron, in the fiducial kinematical region $\pT(\Bhadrn)>9\GeV, |\eta(\Bhadrn)|<2.5$. The measurement is compared with the theoretical predictions, as described in the text. The inner error bars of the data points are statistical uncertainties, the outer are statistical+total systematic uncertainties.