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

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 (≈ 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.