Measurement of long-range multiparticle azimuthal correlations with the subevent cumulant method in pp and p plus Pb collisions with the ATLAS detector at the CERN Large Hadron Collider
Abstract
A detailed study of multiparticle azimuthal correlations is presented using pp data at SQUARE ROOTs = 5.02 and 13 TeV, and p+Pb data at SQUARE ROOTsNN = 5.02 TeV, recorded with the ATLAS detector at the CERN Large Hadron Collider. The azimuthal correlations are probed using four-particle cumulants cn{4} and flow coefficients vn{4} = (-cn{4})^1/4 for n = 2 and 3, with the goal of extracting long-range multiparticle azimuthal correlation signals and suppressing the short-range correlations.
The values of cn{4} are obtained as a function of the average number of charged particles per event, , using the recently proposed two-subevent and three-subevent cumulant methods, and compared with results obtained with the standard cumulant method. The standard method is found to be strongly biased by short-range correlations,which originate mostly from jets with a positive contribution to cn{4}.The three-subevent method, on the other hand, is found to be least sensitive to short-range correlations.