Measurement of σ(bbˉ) with inclusive final states

The conference note is available here (LHCb-CONF-2013-002)

More detailed information: ANA note 2012-022

Abstract

A measurement of the cross section for the production of bbˉ pairs based on b inclusive final states is presented using LHCb data collected from pp collisions at s√= 7 TeV in 2010, corresponding to an integrated luminosity of ∼18 pb−1. The inclusive bbˉ sample is selected on the basis of decay vertices displaced from the primary interaction. The measurement has been performed in a region of pseudorapidity 2.5 <η< 4.0 and transverse momentum pT >5 GeV of the b hadron candidate. The selected sample is a mixture of bbˉ and ccˉ events with a negligible contamination of light quarks, a measurement of the cross section for the production of ccˉ can therefore be performed simultaneously. The results are σbbˉ=7.7±0.12 (stat)±0.84 (syst) μb and σccˉ=104.6±2.7 (stat)±11.4 (syst) μb, inside the kinematic range defined above.

Figures

(Note, eps versions are available under attachments).

Caption	Figure
∆ φ between the b̄b quark pairs: distributions are shown at the very first Pythia production step (continuous red line) and at the last step before hadronization (dotted black line). The distribution for the b hadron pairs is shown in the yellow filled histogram
Difference in azimuthal angles of the two b hadrons for Pythia at the LO approximation (black line) and Powheg at the NLO approximation (blue filled histogram) in the b̄b-inclusive events
Resolution in φ for the seed measured as described in the text for events with one b hadron and one reconstructed seed.
Resolution in θ for the seed measured as described in the text for events with one b hadron and one reconstructed seed.
Distribution of ∆φ of a seed pair before (black line) and after (red histogram) the merging procedure.
Correlations in η between the B0→D−π+ decay, and the seed reconstructed with the particles originating from the signal B0
Correlations in η between the B0→D−π+ decay and the seed reconstructed without the particles originating from the signal B0
Comparison of the transverse momentum of the seed before and after calibration (red histogram and black points respectively), and with true b hadrons (yellow filled histogram), in the fiducial region of the measurement. Distributions are normalized to unity
Distributions of ∆φ of the seeds. Data (black dots), b̄b(yellow light histogram), c̄c (blue dark histogram). Expected contributions of b̄b and c̄c are subsequently added
Distributions of pT of the seeds. Data (black dots), b̄b(yellow light histogram), c̄c (blue dark histogram). Expected contributions of b̄b and c̄c are subsequently added
Response of the BDTG (defined in the text) for data (black dots) fitted with shapes evaluated from simulated b̄b (red dotted line) and c̄c (green dashed line) events. The fit result is indicated by the solid blue line.