Measurement of Nonrandom Event-by-Event Fluctuations of Average Transverse Momentum insNN=200   GeV

S. S. Adler¹,

S. Afanasiev²,

C. Aidala³

et al.

Abstract

Event-by-event fluctuations of the average transverse momentum of produced particles near midrapidity have been measured by the PHENIX Collaboration in square root of (sNN)=200 GeV Au+Au, and p+p collisions at the Relativistic Heavy Ion Collider. The fluctuations are observed to be in excess of the expectation for statistically independent particle emission for all centralities. The excess fluctuations exhibit a dependence on both the centrality of the collision and on the pT range over which the average is calculated. Both the centrality and pT dependence can be well reproduced by a simulation of random particle production with the addition of contributions from hard-scattering processes.

Event-by-event mean $$\varvec{p}_{\mathbf {T}}$$ p T fluctuations in pp and Pb–Pb collisions at the LHC

“…It should be noted, however, that event-averaged radial flow and azimuthal asymmetries are not expected to give rise to strong transverse momentum fluctuations in azimuthally symmetric detectors [13,16]. On the other hand, M( p T ) fluctuations may occur due to fluctuating initial conditions that are also related to event-by-event fluctuations of radial flow and azimuthal asymmetries.…”

“…Event-by-event p T fluctuations have been studied in nucleus-nucleus (A-A) collisions at the Super Proton Synchrotron (SPS) [10][11][12][13][14] and at the Relativistic Heavy-Ion Collider (RHIC) [15][16][17][18][19][20], where dynamical fluctuations have been observed. Fluctuations of p T were found to decrease with collision centrality, as generally expected in a dilution scenario caused by superposition of partially independent e-mail: alice-publications@cern.ch particle-emitting sources.…”

System-size dependence of transverse momentum correlations atsNN=62.4and 200 GeV at the BNL Relativistic Heavy Ion Collider

“…This might indicate the onset of thermalization [26], the onset of jet quenching [3,11], or the saturation of transverse flow in central collisions [38]. The square root of the p t correlations normalized by eventwise average transverse momentum for Cu + Cu and Au + Au collisions is similar for systems with similar N part and is independent of the beam energies studied.…”

“…The saturation of this quantity might indicate effects such as the onset of thermalization [26], the onset of jet quenching [3,11], or the saturation of transverse flow in central collisions [38]. It seems that, for Cu + Cu collisions, this quantity is larger than for Au + Au collisions which might indicate more correlations for the smaller systems.…”

“…The study of event-by-event fluctuations and correlations is an important tool to understand thermalization and phase transitions in heavy-ion collisions [1][2][3][4][5][6]. Non-monotonic change in transverse momentum (p t ) correlations as a function of centrality and/or the incident energy has been proposed as a possible signal of quark gluon plasma (QGP) formation [1].…”