Measurements of low-pT electrons from semileptonic heavy-flavour hadron decays at mid-rapidity in pp and Pb-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV

Abstract

Transverse-momentum (p T) differential yields of electrons from semileptonic heavy-flavour hadron decays have been measured in the most central (0-10%) and in semicentral (20-40%) Pb-Pb collisions at √ s NN = 2.76 TeV. 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 modification 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 p T interval 0.5-3 GeV/c via the nuclear modification factor, R AA. This paper extends the p T reach of the R AA measurement towards significantly lower values with respect to a previous publication. In Pb-Pb collisions the p T-differential measurements of yields at low p T 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.

Charm jet and correlation measurements with ALICE in pp and p -- Pb collisions at the LHC

“…Charm jet and correlation measurement with ALICE in pp and p-Pb Similarly, the Non-HFe contribution, dominated by electrons from gamma conversion and η and π 0 mesons Dalitz decays [9], is removed. Azimuthal correlations are evaluated in pp collisions at √ s = 5.02 TeV, in the integrated transverse momentum range 4 < p e T < 12 GeV/c and in five disjoint p assoc T intervals.…”

Parton distribution functions of heavy mesons on the light front

“…Production of heavy quarkonium, i.e. charmonium (cc) and bottomonium (bb), takes place via initial partonic scattering processes with large momentum transfer on a time scale of ℏ=ð2m ½c;b c 2 Þ, where m is the mass of the quark [1]. Enormous progress has been made on cc and bb decays, showing that many measurements of branching fraction, width, and spectra have attained high precision (see Ref.…”

Low-mass dielectron production in Pb–Pb collisions at √sNN = 2.76 TeV and feasibility of a QGP-temperature measurement

“…The data prefer a reduction of the heavy-flavour components with respect to N coll -scaling, as already visible in the invariant-mass spectrum. This is expected considering the heavy-flavour electron R AA , which is measured to be below unity also in semi-central collisions [ALICE18b].…”

“…This preserves the original mass and momentum distributions and thereby assumes no interactions with the medium. In contrast to this, the nuclear modification factor R AA of electrons from heavy-flavourhadron decays ("heavy-flavour electrons", HFE) has been measured to be below unity [ALICE18b]. The p T dependence of the HFE R AA for central Pb-Pb collisions is shown in the left panel of Figure 5.6.…”

“…Figure 5.6.: Left panel: heavy-flavour electron R AA measurement for 0-10 % centrality[ALICE18b] and parameterization at low p T used for the alternative heavyflavour-cocktail production. Right panel: mass dependence of both heavy-flavour contributions with the R AA applied to their electrons (solid lines) in comparison to the original case (dashed lines).…”