Extraction of multiple parton interactions and color reconnection from forward\u2013backward multiplicity correlations

Abstract

Forward–backward multiplicity correlations have been studied in electron-positron, proton–proton and more recently in lead-lead collisions. For the proton–proton case, comparison of experimental results to different models reveals an incomplete understanding of the physical phenomenon associated with these correlations. In this work, we present a study of forward–backward multiplicity correlations in proton–proton collisions using the PYTHIA event generator, at LHC energies. A detailed analysis is presented with and without weak decays, splitting data samples into soft and hard QCD processes, and comparing the computed correlations for short and long range pseudorapidity regions. Each of these regions is analyzed accounting for the effects of color reconnection and independent multiple parton interactions. We show that a combination of these effects is required to explain the latest measurements on proton–proton data. Furthermore, is shown that from measurements of multiplicity correlations is possible to extract the average number of multiple parton interactions in the event producing these correlations, and albeit model depending, to predict the strength of these correlations, not yet measured, for higher energy collisions.