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

We present a study of τ+τ− lepton pair production in Pb + Pb collisions at . 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.