Forward-central two-particle correlations in p--Pb collisions with ALICE at the LHC

Abstract

We present the results of measurements of two-particle angular correlations between trigger particles reconstructed in the ALICE Forward Muon Spectrometer ($-4.0 < η< -2.5$) and associated particles reconstructed in the central barrel detectors ($|η| < 1.0$) in p--Pb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. At low transverse momentum ($p_{\mathrm{T}}$), the reconstructed trigger particles mainly originate from weak decays of primary pions and kaons, whereas at high $p_{\mathrm{T}}$, they originate mainly from the decay of heavy-flavor particles. The ridge structure elongated in the $η$-direction, discovered recently in p--Pb collisions, is found to persist to the pseudorapidity ranges studied here. The second-order Fourier coefficients of muons are extracted after subtracting the correlations obtained in low-multiplicity events from those in high-multiplicity events. The ratio of coefficients in the Pb-going and p-going directions is presented as a function of $p_{\mathrm{T}}$, and the coefficients are observed to have a similar $p_{\mathrm{T}}$ dependence in both directions with the Pb-going coefficients larger by 16$\pm$6\%. The results are compared with calculations from a multi-phase transport model.