Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV

TL;DR

This paper reports the measurement of the Lambda_b baryon production cross section and the anti-Lambda_b to Lambda_b ratio in proton-proton collisions at 7 TeV, using CMS data and specific decay channels.

Contribution

First measurement of Lambda_b cross section and anti-Lambda_b to Lambda_b ratio as functions of transverse momentum and rapidity at 7 TeV.

Findings

Cross section times branching ratio decreases faster than b mesons with increasing pt.

Measured cross section times branching ratio for pt > 10 GeV is approximately 1.06 nb.

The anti-Lambda_b to Lambda_b ratio is approximately 1.02.

Abstract

The Lambda(b) differential production cross section and the cross section ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7 TeV using data collected by the CMS experiment at the LHC. The measurements are based on Lambda(b) decays reconstructed in the exclusive final state J/Psi Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and Lambda to proton pion, using a data sample corresponding to an integrated luminosity of 1.9 inverse femtobarns. The product of the cross section times the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls faster than that of b mesons. The measured value of the cross section times the branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06 +/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are statistical and systematic, respectively.