Study of identified particle production as a function of transverse event activity classifier, S_T in p-p collisions

A new observable, S_T, is introduced in terms of the sum of the transverse momentum of charged particles (∑_i p_T_i ) produced in proton proton (p-p) collisions at LHC energies to probe the underlying events (UE). The UE are defined as those aspects of proton-proton collisions that are not attributed to the primary hard scattering process, but rather to the accompanying interactions of the rest of the proton. The conventional approach of studying underlying events is usually carried out by defining topological regions with respect to the leading particle in an event. The transverse region is generally sensitive to UE and various classifiers have been used to discriminate the extent of UE activity regions. The production of identified particles like π^±, K^±, p , K_S^0, and Λ^0 are studied in different ranges of transverse activity classifier in p-p collisions at √(s) = 13 TeV using pQCD inspired PYTHIA 8 event generator. A comparative analysis of the identified particle spectra, mean multiplicity and mean transverse momentum has been carried out with respect to S_T and the performance of this new observable is gauged by comparing the results with previously defined R_T observable.