Distributions of Charged Hadrons Associated with High Transverse Momentum Particles inppandAu+AuCollisions atsN

Abstract

Charged hadrons in [EQUATION: SEE TEXT] associated with particles of [EQUATION: SEE TEXT] are reconstructed in pp and Au+Au collisions at sqrt[sNN]=200 GeV. The associated multiplicity and p magnitude sum are found to increase from pp to central Au+Au collisions. The associated p distributions, while similar in shape on the nearside, are significantly softened on the awayside in central Au+Au relative to pp and not much harder than that of inclusive hadrons. The results, consistent with jet quenching, suggest that the awayside fragments approach equilibration with the medium traversed.

Two-gluon correlations in heavy–light ion collisions: Energy and geometry dependence, IR divergences, and kT-factorization

“…In contrast to this behavior, the non-flow correlations in Eqs. (2) and (3) do not seem to require any ellipticity at all to produce a second harmonic (and other even harmonics) in the correlator, resulting in the geometry-dependent non-flow contribution to v 2 which is not ellipticity-driven. This can be seen from the lowest-order correlator in Eq.…”

“…Note that the higher-order corrections to this correlator, which are contained in Eqs. (2) and (3), are likely to regulate some of the IR singularities present in (16), introducing new factors of the saturation scale Q s2 (b), which may modify the geometry-dependence of the lowest-order correlator (16). However, as we will see below, the power-law IR divergences in (16) do not affect the azimuthal angle-dependent correlations; hence our estimate of the magnitude of the Fourier harmonics with index n ≥ 2 should not be affected qualitatively by higher-order corrections.…”

“…Further work is needed to understand the geometry dependence of the full correlator resulting from the two-gluon production cross section in Eqs. (2) and (3).…”

“…The easiest case to factorize, and thus the first one we will cover, is the 'square' diagram component (2). Separating the transverse vectors associated with either one of the valence quarks and emitted gluons, we can write Eq.…”

“…The discovery of the long-range rapidity correlation known as the 'ridge' in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) [2][3][4][5] spurred, among other things, a flurry of activity [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] aimed at better understanding two-particle correlations in the parton saturation/Color Glass Condensate (CGC) physics framework (see [22][23][24][25][26][27] for reviews of the saturation/CGC field). Apart from quantifying how much of the 'ridge' dynamics, which in the meantime was also observed by experiments at the Large Hadron Collider (LHC) in proton-proton (pp) and protonnucleus (pA) collisions [28][29][30][31], is due to the initial-state saturation effects, the problem of two-gluon production in nucleus-nucleus (AA) collisions is an important theoretical problem in its own right, allowing us to gain a new insight in the nonlinear dynamics of strong gluon fields in the initial stages of heavy ion collisions.…”