Measurement of the energy response of the ATLAS calorimeter to charged pions from W-+/- -> tau(+/-) (->pi(+/-)nu(tau))nu(tau) events in Run 2 data

The energy response of the ATLAS calorimeter is measured for singlecharged pions with transverse momentum in the range 10< 300 GeV.The measurement is performed using 139 fb(-1) of LHC proton-protoncollision data at root s =13 TeV taken in Run 2 by the ATLAS detector.Charged pions originating from tau-lepton decays are used to provide asample of high-p(T) isolated particles, where the composition is known,to test an energy regime that has not previously been probed by in situsingle-particle measurements. The calorimeter response to single-pionsis observed to be overestimated by similar to 2\% across a large part ofthe p(T) spectrum in the central region and underestimated by similar to4\% in the endcaps in the ATLAS simulation. The uncertainties in themeasurements are less than or similar to 1\% for 15<185 GeV in thecentral region. To investigate the source of the discrepancies, thewidth of the distribution of the ratio of calorimeter energy to trackmomentum, the energies per layer and response in the hadroniccalorimeter are also compared between data and simulation.