Flattenicity as "centrality" estimator in p-Pb collisions simulated with PYTHIA 8.312 Angantyr

In this paper, a "centrality" estimator based on flattenicity (ρ) is studied in proton-led (p-Pb) collisions at √sNN=5.02 TeV using PYTHIA 8 Angantyr. Although Angantyr is still under development, the existing implementation is enough to study the particle production in systems where medium effects are absent. Firstly, ALICE data on pseudorapidity distributions as a function of the forward multiplicity (V0M), as well as transverse momentum distributions of identified particles in non-single diffractive p-Pb collisions, are compared with Angantyr. Secondly, the average number of binary nucleon-nucleon (Ncoll) collisions for different "centrality" estimators are compared. The studies include the following "centrality" estimators: V0M, ρ and midrapidity multiplicity (CL1). On one hand, the "centrality" dependence of Ncoll for the ρ selection shows the smallest deviations ($<8$ %) with respect to that obtained using impact parameter b; on the other hand, the V0M and CL1 yield huge deviations (up to a factor 2) with respect to the results using b. The particle ratios and nuclear modification factors (QpPb) as a function of pT are also studied. The proton-to-pion ratio exhibits a flow-like peak at intermediate pT (2-8 GeV/c) with little or no "centrality" dependence for V0M, ρ and b selections. The kaon-to-pion ratio as a function of pT is "centrality" independent for the same selections. On the contrary, for the CL1 class the ratios exhibit the typical behaviour associated with hard physics. Regarding QpPb, a peak at intermediate pT ($2-8$ GeV/c) for different particle species is observed when the "centrality" is obtained with b or ρ. The observed features diminish for the selections based on V0M and CL1.