Transverse momentum correlations in p-Pb and Pb-Pb collisions in ALICE at the LHC

Two-particle correlations provide information about particle production mecha- nisms in heavy-ion collisions. We report on the study of two particle transverse momentum correlations (∆ p T ∆ p T ) in Pb-Pb collisions at √ s NN = 2.76 TeV and in p-Pb collisions at √ s NN = 5.02 TeV measured with the ALICE detector. Unlike the particle number correlation functions, ∆ p T ∆ p T measures transverse momentum correlations between particle pairs. The p T dependence of this correlation measure may make it amenable to probe the fluctuations in temperature, average momentum, flow, hardness of spectrum and hardness of correlations (jet vs non-jets). Correlation functions for ++, −− , + − , and − + charged particle pairs as a function of pair azimuthal and pseudo-rapidity separation (∆ φ , ∆ η ) are measured. The infor- mation from the above charged pairs are combined into a charge independent (CI) correlation. We study their evolution with collision centrality and particle multiplicity per event. We find that ∆ p T ∆ p T correlation shapes exhibit a strong centrality dependence in Pb-Pb collisions and multiplicity dependence in p-Pb collisions. The correlation function is everywhere posi- tive, indicating that both particles from a pair are more likely to have momentum above or below the average transverse momentum in an event ensemble. We further study the Fourier decomposition of the correlation functions dependence on ∆ φ as a function of ∆ η .