Measurement of (2S) production as a function of charged-particle pseudorapidity density in pp collisions at √s=13 TeV and p-Pb collisions at √sNN=8.16 TeV with ALICE at the LHC

Production of inclusive charmonia in pp collisions at center-of-mass energy of root s = 13TeV and p-Pb collisions at center-of-mass energy per nucleon pair of root sNN = 8.16TeV is studied as a function of charged-particle pseudorapidity density with ALICE. Ground and excited charmonium states ( J/psi, psi(2S)) are measured from their dimuon decays in the interval of rapidity in the center-of-mass frame 2.5 < y(cms) < 4.0 for pp collisions, and 2.03 < y(cms) < 3.53 and -4.46 < y(cms) < -2.96 for p-Pb collisions. The charged-particle pseudorapidity density is measured around midrapidity (| eta | < 1.0). In pp collisions, the measured charged-particle multiplicity extends to about six times the average value, while in p-Pb collisions at forward (backward) rapidity a multiplicity corresponding to about three (four) times the average is reached. The psi(2S) yield increases with the charged-particle pseudorapidity density. The ratio of psi(2S) over J/ yield does not show a significant multiplicity dependence in either colliding system, suggesting a similar behavior of J/ and psi(2S) yields with respect to charged-particle pseudorapidity density. Results for the psi(2S) yield and its ratio with respect to J/psi agree with available model calculations.