Measurement of the Λb cross section and the Λ¯b to Λb ratio with J/ψΛ decays in pp collisions at s=7 TeV

The Λb differential production cross section and the cross section ratio σ(Λ¯b)/σ(Λb) are measured as functions of transverse momentum pTΛb and rapidity |yΛb| in pp collisions at s=7 TeV using data collected by the CMS experiment at the LHC. The measurements are based on Λb decays reconstructed in the exclusive final state J/ψΛ, with the subsequent decays J/ψ→μ+μ− and Λ→pπ, using a data sample corresponding to an integrated luminosity of 1.9 fb−1. The product σ(Λb)×B(Λb→J/ψΛ) versus pTΛb falls faster than that of b mesons. The measured value of σ(Λb)×B(Λb→J/ψΛ) for pTΛb>10 GeV and |yΛb|<2.0 is 1.16±0.06±0.12nb, and the integrated σ(Λ¯b)/σ(Λb) ratio is 1.02±0.07±0.09, where the uncertainties are statistical and systematic, respectively.