Measurement of B anti-B Angular Correlations based on Secondary Vertex Reconstruction at sqrt(s)=7 TeV

TL;DR

This paper measures the angular correlations between beauty and anti-beauty hadrons at 7 TeV, revealing a significant number of pairs with small angular separation, thus testing QCD predictions.

Contribution

First measurement of B B-bar angular correlations at small angles using secondary vertex reconstruction at the LHC.

Findings

A sizable fraction of B B-bar pairs are produced with small opening angles.

The differential cross section data provides new insights into b b-bar production dynamics.

Results test and inform QCD models of heavy quark production.

Abstract

A measurement of the angular correlations between beauty and anti-beauty hadrons (B B-bar) produced in pp collisions at a centre-of-mass energy of 7 TeV at the CERN LHC is presented, probing for the first time the region of small angular separation. The B hadrons are identified by the presence of displaced secondary vertices from their decays. The B hadron angular separation is reconstructed from the decay vertices and the primary-interaction vertex. The differential B B-bar production cross section, measured from a data sample collected by CMS and corresponding to an integrated luminosity of 3.1 inverse picobarns, shows that a sizable fraction of the B B-bar pairs are produced with small opening angles. These studies provide a test of QCD and further insight into the dynamics of b b-bar production.