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

A measurement is presented of the Z/γ∗ → ττ cross section in pp collisions at √s = 13 TeV, using data recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 2.3 fb^(−1). The product of the inclusive cross section and branching fraction is measured to be σ(pp → Z/γ∗ + X)B(Z/γ∗ → ττ) = 1848 ± 12(stat) ± 67 (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 τ lepton production. The measurement also provides the reconstruction efficiency and energy scale for τ decays to hadrons + ν_τ final states, determined with respective relative uncertainties of 2.2 and 0.9%.