Measurement of beauty-hadron decay electrons in Pb--Pb collisions at sqrt(s_NN) = 2.76 TeV with ALICE

TL;DR

This paper reports on the measurement of electrons from beauty-hadron decays in Pb--Pb collisions at 2.76 TeV, providing insights into the properties of the Quark-Gluon Plasma through impact parameter analysis and statistical separation techniques.

Contribution

It introduces a method to statistically separate beauty decay electrons from background using impact parameter distributions and maximum likelihood fitting in heavy-ion collisions.

Findings

Observed significant suppression of beauty decay electrons at high transverse momentum

Demonstrated the effectiveness of impact parameter-based separation techniques

Provided data on the nuclear modification factor for beauty-hadron decay electrons

Abstract

The ALICE Collaboration at the LHC studies heavy-ion collisions to investigate the properties of the Quark-Gluon Plasma (QGP). Heavy quarks (charm and beauty) are effective probes for this purpose. Both their energy loss in the medium as well as their possible thermalization yield information about the medium properties. Experimentally, the reconstruction of hadrons with charm valence quarks is possible. For hadrons with beauty valence quarks a promising strategy is the measurement of their decay electrons. To separate these from the background electrons (mainly from charm hadron decays, photon conversions or light-meson decays) the large decay length of beauty hadrons can be utilized. It leads to a relatively large typical impact parameter of the decay electrons. By comparing the impact parameter distribution of the signal electrons with those from the background sources, the signal can be statistically separated from the background. For this purpose a maximum likelihood fit is employed using impact parameter distribution templates from simulations. The resulting nuclear modification factor for electrons from beauty-hadron decays shows a sizeable suppression for p_T > 3 GeV, albeit still with large uncertainties.