Simulation studies of R2(Δη,Δφ) and P2(

Abstract

We report studies of charge-independent (CI) and charge-dependent (CD) two-particle differentialnumber correlation functions, R2 (∆η, ∆ϕ), and transverse momentum (p T ) correlation functions, P2 (∆η, ∆ϕ), 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 (p/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 R2 and P2 correlators as these pertain to recent measurements by the ALICE collaboration. The R2 and P2 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 R2 and P2 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 ∆η dependence of R2 and P2 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).

Measurement of $R_{2}(\Delta\eta, \Delta\varphi)$ and $P_{2}(\Delta\eta, \Delta\varphi)$ correlation functions in pp collisions at $\sqrt{\textit{s}}$ = 13~TeV using ALICE data

“…Similarly, the width of the near side of the 𝑃 CD 2 (Δ𝜑) correlator is also significantly smaller than that of the 𝑅 CD 2 (Δ𝜑) correlator. This difference is expected due to the angular and transverse momentum ordering [4].…”

“…In p-Pb collisions, the widths of 𝑅 CD 2 decrease, while the widths of 𝑃 CD 2 increase. This is related to the angular ordering [4] of the p T of the jet constituents, which leads to a narrowing of the width of 𝑅 CD 2 . In pp collisions, the widths of 𝑅 CD 2 (Δ𝜑) and 𝑃 CD 2 (Δ𝜑) are in good agreement with the peripheral p-Pb collisions.…”

Transverse spherocity and multiplicity dependence of $R_{2}$ and $P_{2}$ correlation functions in pp collisions

“…The near-and awayside peak of 𝑅 2 and 𝑃 2 are more prominent and distinuishable for spherocity classes as compared to multiplicity classes. Again, 𝑃 2 has a smaller width than 𝑅 2 due to angular ordering [4] of the p T of jet constituents.…”

Differential two-particle number and momentum correlations with the AMPT, UrQMD, and EPOS models in Pb-Pb collisions at $\sqrt{\textit{s}_{_{\rm NN}}}$= 2.76 TeV

“…Furthermore, a change from positive to negative values is expected as a function of ∆η and ∆ϕ in the vicinity of the near-side peak for correlations involving jet fragments with a specific p T vs. θ ordering (θ being the angle of particle emission relative to the initial parton direction) as shown in Ref. [41]. Such change from positive to negative values might also be observed in the presence of resonance decays with large radial boost [42].…”