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

The production of electrons from beauty-hadron decays was measured at midrapidity in proton-proton (pp) and central Pb-Pb collisions at center-of-mass energy per nucleon-nucleon pair $\sqrt{s_{\rm NN}}$ = 5.02 TeV, using the ALICE detector at the LHC. The cross section measured in pp collisions in the transverse momentum interval $2 <~ p_{\rm T} <~ 8$ GeV/$c$ was compared with models based on perturbative quantum chromodynamics calculations. The yield in the 10% most central Pb-Pb collisions, measured in the interval $2 <~ p_{\rm T} <~ 26$ GeV/$c$, was used to compute the nuclear modification factor $R_{\rm AA}$, extrapolating the pp reference cross section to $p_{\rm T}$ larger than 8 GeV/$c$. The measured $R_{\rm AA}$ shows significant suppression of the yield of electrons from beauty-hadron decays at high $p_{\rm T}$ and does not show a significant dependence on $p_{\rm T}$ above 8 GeV/$c$ within uncertainties. The results are described by several theoretical models based on different implementations of the interaction of heavy quarks with a quark-gluon plasma, which predict a smaller energy loss for beauty quarks compared to light and charm quarks.

 

Phys. Rev. C 108 (2023) 034906
HEP Data
e-Print: arXiv:2211.13985 | PDF | inSPIRE
CERN-EP-2022-238
Figure group

Figure 1

Examples of the impact parameter fits with the four-template fit approach used in the TPC--TOF analyses. The left panel shows a fit with templates for the four classes of electron sources in pp collisions at $\sqrt{s} = 5.02 {\rm TeV}$ in the lowest $\pt$ interval and the right panel shows a fit example in Pb--Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02 {\rm TeV}$ in the highest $\pt$ range.

Figure 2

Example of the impact parameter distributions used in the TPC--EMCal analysis in 0--10\% Pb--Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02 {\rm TeV}$. The hadron contamination (red), photonic electron (purple), and inclusive electron (black) $d_{0}$ distributions are shown in the left panel. The right panel shows an example of a fit with the two template approach.

Figure 3

$\pt$-differential cross section of electrons from beauty-hadron decays in pp collisions at $\sqrt{s}=5.02 {\rm TeV}$ using TPC--TOF for electron identification. In the upper panel, the cross section is compared with FONLL  and GM-VFNS  predictions. The ratios of data to these calculations are reported in the bottom panels.

Figure 4

Yield of beauty-hadron decay electrons in 0--10\% central Pb--Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02$ TeV for the TPC--TOF and TPC--EMCal analyses compared with the pp reference scaled by $\langle T_{\rm AA} \rangle$, obtained from the measured cross section for $\pt < 8$ GeV/$c$, which is extrapolated up to $p_\mathrm{T}= 26$ GeV/$c$ using FONLL. The ratio of the yields using TPC--TOF and TPC--EMCal analyses in the overlapping interval of $3 < \pt < 8$ GeV/$c$ in Pb--Pb collisions is shown in the bottom panel.

Figure 5

Nuclear modification factor of electrons from beauty-hadron decays in the $10\%$ most central Pb--Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02 {\rm TeV}$. Left: Comparison with $R_{\rm AA}$ of muons from beauty-hadron decays measured by the ATLAS Collaboration . Right: comparison with the measurements of $R_{\rm AA}$ of electrons from heavy-flavor hadron (beauty plus charm) decays , and with the $R_{\rm AA}$ of muons from charm-hadron decays measured by the ATLAS Collaboration .

Figure 6

Nuclear modification factor of electrons from beauty-hadron decays in the $10\%$ most central Pb--Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02 {\rm TeV}$ compared with predictions from several theoretical calculations. Left: Comparison with predictions from DREENA-B  and DAB-MOD M\&T  models for electrons from beauty and charm decays. Right: Comparison with predictions from MC@sHQ , PHSD , and LIDO  calculations for electrons from beauty decays.