Measurement of electrons from beauty-hadron decays in p-Pb collisions at s N N = 5.02 √sNN=5.02 TeV and Pb-Pb collisions at s N N = 2.76 √sNN=2.76 TeV

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The production of beauty hadrons was measured via semi-leptonic decays at mid-rapidity with the ALICE detector at the LHC in the transverse momentum interval 1 < p T < 8 GeV/c in minimum-bias p-Pb collisions at s NN = 5.02 TeV and in 1.3 < p T < 8 GeV/c in the 20% most central Pb-Pb collisions at s NN = 2.76 TeV. The pp reference spectra at s = 5.02 TeV and s = 2.76 TeV, needed for the calculation of the nuclear modification factors R pPb and R PbPb , were obtained by a pQCD-driven scaling of the cross section of electrons from beauty-hadron decays measured at s = 7 TeV. In the p T interval 3 < p T < 8 GeV/c, a suppression of the yield of electrons from beauty-hadron decays is observed in Pb-Pb compared to pp collisions. Towards lower p T , the R PbPb values increase with large systematic uncertainties. The R pPb is consistent with unity within systematic uncertainties and is well described by theoretical calculations that include cold nuclear matter effects in p-Pb collisions. The measured R pPb and these calculations indicate that cold nuclear matter effects are small at high transverse momentum also in Pb-Pb collisions. Therefore, the observed reduction of R PbPb below unity at high p T may be ascribed to an effect of the hot and dense medium formed in Pb-Pb collisions.