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

Abstract

We present a study of ${\tau }^{+}{\tau }^{-}$ lepton pair production in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 5.5 TeV. The larger ${\tau }^{\pm }$ mass ($\sim$ 1.77 GeV) compared to $e^{\pm }$ and ${\mu }^{\pm }$ leads to considerably small hadronic contribution to the ${\tau }^{+}{\tau }^{-}$ 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 ${\tau }^{+}{\tau }^{-}$. We observe that the contribution from Drell-Yan process dominates over thermal yield for ${\tau }^{+}{\tau }^{-}$ pair mass from 4 to 20 GeV at the LHC energy. We also present the ratio of $\tau$ 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 $\tau$ 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 ${\tau }^{+}{\tau }^{-}$ pair from quark gluon plasma (QGP) in the mass window $4\le M$(GeV)$\le 6$.

Comments: Five pages with one LaTeX file and three eps files for figures