Measurements of low-pT electrons from semileptonic heavy-flavour hadron decays at mid-rapidity in pp and Pb-Pb collisions at √s NN = 2.76 TeV

Abstract

Transverse-momentum (pT) differential yields of electrons from semileptonic heavy-flavour hadron decays have been measured in the most central (0–10%) and in semi- central (20–40%) Pb–Pb collisions at √sNN = 2.76TeV. The corresponding production cross section in pp collisions has been measured at the same energy with substantially reduced systematic uncertainties with respect to previously published results. The modifi- cation of the yield in Pb–Pb collisions with respect to the expectation from an incoherent superposition of nucleon-nucleon collisions is quantified at mid-rapidity (|y| < 0.8) in the pT interval 0.5–3GeV/c via the nuclear modification factor, RAA. This paper extends the pT reach of the RAA measurement towards significantly lower values with respect to a previous publication. In Pb–Pb collisions the pT-differential measurements of yields at low pT are essential to investigate the scaling of heavy-flavour production with the number of binary nucleon-nucleon collisions. Heavy-quark hadronization, a collective expansion and even initial-state effects, such as the nuclear modification of the Parton Distribution Function, are also expected to have a significant effect on the measured distribution.