Event plane dependence of the flow modulated background in dihadron and jet-hadron correlations in heavy ion collisions

Abstract

Di-hadron and jet-hadron correlations are commonly used in relativistic heavy ion collisions to study the soft component of jets in a quark gluon plasma. There is a large correlated background which is described by the Fourier decomposition of the azimuthal anisotropy where vn is the nth order coefficient. The path length dependence of partonic energy loss can be studied by varying the angle of the high momentum trigger particle or jet relative to a reconstructed event plane. This modifies the shape of the background correlated with that event plane. The original derivation of the shape of this background only considered correlations relative to the second order event plane, which is correlated to the initial participant plane. We derive the shape of this background for an event plane at an arbitrary order. There is a phase shift in the case of jets restricted to asymmetric regions relative to the event plane. For realistic correlations between event planes, the correlation between the second and fourth order event planes leads to a much smaller effect than the finite event plane resolution at each order. Finally, we assess the status of the rapidity even v1 term due to flow, which has been measured to be comparable to v2 and v3 terms. 25.75.Gz,25.75.Bh

Jet-hadron correlations measured relative to the second order event plane in Pb-Pb collisions at sNN=2.76TeV

“…where φ s is the center of the azimuthal range of the trigger particle relative to the event plane, c is the width of that range, N t is the number of triggers, N a is the number of associated particles, v assoc n are the v n of the associated particles, v trig n are the v n of the triggers, and R n is the event plane resolution given in Eq. (3) [66,67]. Terms v n with n < 1 are zero.…”

Event Plane Dependence of Jet-Hadron Correlations in Au–Au Collisions at √sNN = 200 GeV with the STAR Detector at RHIC

“…When the trigger jet is restricted relative to the event plane, both the background level and effective v n of the trigger are modified and will contain a dependence on the event plane resolution. The derivation of the event plane dependent background equations are given in [8] with more extensive descriptions given in [9]. The event plane resolution is used to correct for the difference between the reconstructed event plane and the underlying symmetry plane, ψ n [10].…”

Event plane dependence of jet quenching studied via azimuthal correlations and differential jet shape in Au--Au collisions at $\sqrt{s_{NN}}=200$ GeV with the STAR detector at RHIC

“…When the trigger is restricted relative to the event plane, both the level of the background and the effective v n of the trigger are modified and will contain a dependence on the resolution of the event plane. This new formalism is derived for two-particle correlations at different orientations to the reaction plane in [11,12]. The resolutions of the event plane, ℜ, are used to correct for the experimental difference between the reconstructed event plane and the underlying symmetry plane, ψ n .…”