Measurement of event-shape observables in Z→ℓ+ℓ− events in pp collisions at s√=7 TeV with the ATLAS detector at the LHC
We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of MINECO, Spain and EPLANET, ERC, FP7, Horizon 2020 and Marie Skłodowska-Curie Actions, European Union. Funded by SCOAP3. ; Event-shape observables measured using charged particles in inclusive Z -boson events are presented, using the electron and muon decay modes of the Z bosons. The measurements are based on an integrated luminosity of of proton-proton collisions recorded by the ATLAS detector at the LHC at a centre-of-mass energy . Charged-particle distributions, excluding the lepton-antilepton pair from the Z -boson decay, are measured in different ranges of transverse momentum of the Z boson. Distributions include multiplicity, scalar sum of transverse momenta, beam thrust, transverse thrust, spherocity, and -parameter, which are in particular sensitive to properties of the underlying event at small values of the Z -boson transverse momentum. The measured observables are compared with predictions from P 8, S, and H 7. Typically, all three Monte Carlo generators provide predictions that are in better agreement with the data at high Z -boson transverse momenta than at low Z -boson transverse momenta, and for the observables that are less sensitive to the number of charged particles in the event.