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,has been measured with the cumulant method using the ATLAS detector at the LHC. In a data sample corresponding to an integrated luminosity of approximately 1μb−1, the paramete rv2 has been obtained using two-and four-particle cumulants over the pseudorapidity range |η|<2.5. The results are presented as a function of transverse momentum and the event activity, defined in terms of the transverse energy summed over 3.1<η<4.9 in the direction of the Pb beam. They show features characteristic of collective anisotropic flow, similar to that observed in Pb+Pb collisions. A comparison is made to results obtained using two-particle correlation methods, and to predictions from hydrodynamic models of p+Pb collisions. Despite the small transverse spatial extent of the p+Pb collision system, the large magnitude of v2 and its similarity to hydrodynamic predictions provide additional evidence for the importance of final-state effects in p+Pb reactions.

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

CONTA, CLAUDIO;FRANCHINO, SILVIA;FRATERNALI, MARCO;LIVAN, MICHELE;NEGRI, ANDREA;REBUZZI, DANIELA MARCELLA;RIMOLDI, ADELE;
2013

Abstract

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,has been measured with the cumulant method using the ATLAS detector at the LHC. In a data sample corresponding to an integrated luminosity of approximately 1μb−1, the paramete rv2 has been obtained using two-and four-particle cumulants over the pseudorapidity range |η|<2.5. The results are presented as a function of transverse momentum and the event activity, defined in terms of the transverse energy summed over 3.1<η<4.9 in the direction of the Pb beam. They show features characteristic of collective anisotropic flow, similar to that observed in Pb+Pb collisions. A comparison is made to results obtained using two-particle correlation methods, and to predictions from hydrodynamic models of p+Pb collisions. Despite the small transverse spatial extent of the p+Pb collision system, the large magnitude of v2 and its similarity to hydrodynamic predictions provide additional evidence for the importance of final-state effects in p+Pb reactions.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11571/703819
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