Underlying-Event Studies With Strange Hadrons in Pp Collisions at √s=13 Tev With the Atlas Detector

Abstract

Properties of the underlying-event in pp interactions are investigated primarily via the strange hadrons K-S(0), Lambda and (Lambda) over bar, as reconstructed using the ATLAS detector at the LHC in minimum-bias pp collision data at root s = 13 TeV. The hadrons are reconstructed via the identification of the displaced two-particle vertices corresponding to the decay modes K-S(0) -> pi(+) pi(-), Lambda -> pi(-) p and (Lambda) over bar -> pi(+) (p) over bar. These are used in the construction of underlying-event observables in azimuthal regions computed relative to the leading charged-particle jet in the event. None of the hadronisation and underlying-event physicsmodels considered can describe the data over the full kinematic range considered. Events with a leading charged-particle jet in the range of 10 < p(T) <= 40 GeV are studied using the number of prompt charged particles in the transverse region. The ratio N(Lambda + <(Lambda)over bar>)/N(K-S(0)) as a function of the number of such charged particles varies only slightly over this range. This disagrees with the expectations of some of the considered Monte Carlo models.