Simulation studies of R_2(Δη, Δφ) and P_2(Δη, Δφ) correlation functions in pp collisions with the PYTHIA and HERWIG models

We report studies of charge-independent (CI) and charge-dependent (CD) two-particle differential-number correlation functions, R_2(Δη, Δφ), and transverse momentum (p_ T) correlation functions, P_2(Δη, Δφ), of charged particles in √(s) = 2.76 TeV pp collisions with the PYTHIA and HERWIG models. Model predictions are presented for inclusive charged hadrons (h^±), as well as pions (π^±), kaons (K^±), and (anti-)protons (p̅/p) in the ranges 0.2 < p_ T≤ 2.0 GeV/c, 2.0 < p_ T≤ 5.0 GeV/c, and 5.0 < p_ T≤ 30.0 GeV/c, with full azimuthal coverage in the range |η|< 1.0. We compare the model predictions for the strength and shape of the R_2 and P_2 correlators as these pertain to recent measurements by the ALICE collaboration. The R_2 and P_2 correlation functions estimated with PYTHIA and HERWIG exhibit qualitatively similar near-side and away-side correlation structures but feature important differences. Our analysis indicates that comparative studies of R_2 and P_2 correlation functions would provide valuable insight towards the understanding of particle production in pp collisions, and by extension, should also be useful in studies of heavy-ion collisions. Comparison of the Δη dependence of R_2 and P_2 could contribute, in particular, to a better understanding and modeling of the angular ordering of particles produced by hadronization in jets, as well as a better description of jet fragmentation functions of identified species at low momentum fraction (z).