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Measurement of electrons from beauty-hadron decays in p-Pb collisions at $\mathbf{\sqrt{s_{\rm NN}}=5.02}$ TeV and Pb-Pb collisions at $\mathbf{\sqrt{s_{\rm NN}}=2.76}$ TeV

The ALICE collaboration
No Journal Information, 2016

Abstract (data abstract)
CERN-LHC. 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 $1 <p_{\rm T}<8~\textrm{GeV}/c$ in minimum-bias p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$~TeV and in $1.3 <p_{\rm T}<8~\textrm{GeV}/c$ in the 20\% most central Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$~TeV. The pp reference spectra at $\sqrt{s} = 5.02$~TeV and $\sqrt{s} = 2.76$~TeV, needed for the calculation of the nuclear modification factors $R_{\rm pPb}$ and $R_{\rm PbPb}$, were obtained by a pQCD-driven scaling of the cross section of electrons from beauty-hadron decays measured at $\sqrt{s} = 7$ TeV. In the $p_{\rm T}$ interval $3 <p_{\rm T}<8~\textrm{GeV}/c$ a suppression of the yield of electrons from beauty-hadron decays is observed in Pb-Pb compared to pp collisions. Towards lower $p_{\rm T}$, the $R_{\rm PbPb}$ values increase with large systematic uncertainties. The $R_{\rm pPb}$ 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 $R_{\rm pPb}$ 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 $R_{\rm PbPb}$ below unity at high $p_{\rm T}$ may be ascribed to an effect of the hot and dense medium formed in Pb-Pb collisions.

  • Table 1

    Data from Figure 5 (left)

    10.17182/hepdata.77904.v1/t1

    Invariant cross section of electrons from beauty-hadron decays as a function of transverse momentum in minimum-bias p--Pb collisions in the...

  • Table 2

    Data from Figure 5 (right)

    10.17182/hepdata.77904.v1/t2

    Invariant yield of electrons from beauty-hadron decays as a function of transverse momentum in 20% most central Pb--Pb collisions.

  • Table 3

    Data from Figure 6 (left, blue)

    10.17182/hepdata.77904.v1/t3

    Nuclear modification factor $R_{\text{pA}}$ of electrons from beauty-hadron decays as a function of transverse momentum for minimum-bias p--Pb collisions in...

  • Table 4

    Data from Figure 6 (left, red)

    10.17182/hepdata.77904.v1/t4

    Nuclear modification factor $R_{\text{AA}}$ of electrons from beauty-hadron decays as a function of transverse momentum for 20% most central Pb--Pb...

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