Heavy lepton pair production in nucleus–nucleus collisions at LHC energy – a case study

Abstract

We present a study of τ + τ − lepton pair production in Pb+Pb collisions at √ sNN = 5.5 TeV.The larger τ ± mass (∼ 1.77 GeV) compared to e ± and µ ± leads to considerably small hadronic contribution to the τ + τ − pair invariant mass (M ) distribution relative to the production from thermal partonic sources. The quark-anti-quark annihilation processes via intermediary virtual photon, Z and Higgs bosons have been considered for the production of τ + τ − . We observe that the contribution from Drell-Yan process dominates over thermal yield for τ + τ − pair mass from 4 to 20 GeV at the LHC energy. We also present the ratio of τ lepton pair yields for nucleus-nucleus collisions relative to yields from p+p collisions scaled by number of binary collisions at LHC energies as a function τ pair mass. The ratio is found to be significantly above unity for the mass range 4 to 6 GeV. This indicates the possibility of detecting τ + τ − pair from quark gluon plasma (QGP) in the mass window 4 ≤ M (GeV)≤ 6.