Measurement with the ATLAS detector of multi-particle azimuthal correlations in p+Pb collisions at sNN−−−−√=5.02 TeV

ATLAS COLLABORATION, G. AAD, F. MONTICELLI, ET AL

PHYSICS LETTERS B

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 231 p. 1 - 23

0370-2693

In order to study further the long-range correlations (?ridge?) observed recently in p+Pb collisions√at sNN = 5.02 TeV, the second-order azimuthal anisotropy parameter of charged particles, v2 , hasbeen measured with the cumulant method using the ATLAS detector at the LHC. In a data samplecorresponding to an integrated luminosity of approximately 1 μb−1 , the parameter v2 has been ob-tained using two- and four-particle cumulants over the pseudorapidity range |η| < 2.5. The resultsare presented as a function of transverse momentum and the event activity, defined in terms of thetransverse energy summed over 3.1 < η < 4.9 in the direction of the Pb beam. They show featurescharacteristic of collective anisotropic flow, similar to that observed in Pb+Pb collisions. A comparisonis made to results obtained using two-particle correlation methods, and to predictions from hydrody-namic models of p+Pb collisions. Despite the small transverse spatial extent of the p+Pb collisionsystem, the large magnitude of v2 and its similarity to hydrodynamic predictions provide additionalevidence for the importance of final-state effects in p+Pb reactions.