Measurement of the Z/γ* → ττ cross section in pp collisions at √s = 13 TeV and validation of τ lepton analysis techniques

Abstract

A measurement is presented of the \(Z/{\gamma }^{\ast }\to \tau \tau \) cross section in \(\text{pp}\) collisions at \(\sqrt{s}=13\phantom{\rule{0.333333em}{0ex}}\text{TeV}\), using data recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of \(2.3\phantom{\rule{0.333333em}{0ex}}{\text{fb}}^{-1}\). The product of the inclusive cross section and branching fraction is measured to be \(\sigma \left(\text{pp}\to Z/{\gamma }^{\ast }\text{+X}\right)\phantom{\rule{0.166667em}{0ex}}B\left(Z/{\gamma }^{\ast }\to \tau \tau \right)=1848±12\phantom{\rule{0.166667em}{0ex}}\left(\text{stat}\right)±67\phantom{\rule{0.333333em}{0ex}}\text{(syst \,+\,lumi) pb}\), in agreement with the standard model expectation, computed at next-to-next-to-leading order accuracy in perturbative quantum chromodynamics. The measurement is used to validate new analysis techniques relevant for future measurements of \(\tau \) lepton production. The measurement also provides the reconstruction efficiency and energy scale for \(\tau \) decays to hadrons \(\phantom{\rule{0.166667em}{0ex}}+\phantom{\rule{0.166667em}{0ex}}{\nu }_{\tau }\) final states, determined with respective relative uncertainties of 2.2 and 0.9%.