Separation of the Charm and Beauty Production in p--Pb and Pb--Pb Collisions with ALICE

TL;DR

This paper reports on ALICE's measurements of charm and beauty quark production in p--Pb and Pb--Pb collisions, revealing medium-induced modifications especially for beauty quarks in heavy-ion collisions.

Contribution

It introduces a method to separate electrons from beauty-hadron decays using decay length, enabling detailed study of beauty quarks in quark-gluon plasma.

Findings

Significant modification of beauty electron spectra in central Pb--Pb collisions.

No notable change in p--Pb collisions compared to proton-proton.

Supports the idea that observed modifications are due to hot medium effects.

Abstract

Measurements of heavy (charm and beauty) quarks provide useful insights into the properties of the quark--gluon plasma. The good particle identification capabilities of ALICE make a measurement based on the electrons from semi-leptonic decays of heavy-flavour hadrons feasible. This approach makes use of the large branching ratios ($\approx 10-20\%$) of heavy--flavour hadrons into electrons. Separation of the contribution from beauty-hadron decay electrons was achieved by utilizing the large decay length of the associated hadrons, making the investigation of beauty quarks in the medium possible. By comparing measurements in p--Pb and Pb--Pb collisions, it is possible to disentangle effects of cold nuclear matter from those of the hot and dense medium. The results show a strong change in the transverse momentum distribution of electrons from beauty-hadron decays in central Pb--Pb collisions with respect to the proton--proton case. No significant change from proton--proton collisions can be seen in the p--Pb case, suggesting that the modification is a final state effect.