Mach Cone Induced byγ-Triggered Jets in High-Energy Heavy-Ion Collisions

Abstract

Medium excitation by jet shower propagation inside a quark-gluon plasma is studied within a linear Boltzmann transport and a multiphase transport model. Contrary to the naive expectation, it is the deflection of both the jet shower and the Mach-cone-like excitation in an expanding medium that is found to gives rise to a double-peak azimuthal particle distribution with respect to the initial jet direction. Such deflection is the strongest for hadron-triggered jets which are often produced close to the surface of dense medium due to trigger-bias and travel against or tangential to the radial flow. Without such trigger bias, the effect of deflection on γ-jet showers and their medium excitation is weaker. Comparative study of hadron and γ-triggered particle correlations can therefore reveal the dynamics of jet-induced medium excitation in high-energy heavy-ion collisions.PACS numbers: 25.75.Bh,25.75.Cj,25.75.Ld Strong jet quenching has been observed in experiments [1][2][3][4] at the Relativistic Heavy-ion Collider (RHIC) as a consequence of jet quenching or parton energy loss in high-energy heavy-ion collisions [5]. The energy and momentum lost by a propagating parton will be carried by radiated gluons and recoiled medium partons which in turn will go through further interaction and eventually lead to collective medium excitation such as supersonic waves or Mach cones [6,7]. Indeed, Mach cones have been found in the solutions of both hydrodynamic response [8][9][10][11][12] and linearized Einstein equations in string theory [13,14] excited by a propagating jet. Such collective excitation by a propagating jet is expected to be responsible for the observed conic back-to-back (b2b) azimuthal dihadron [15,16] and trihadron correlations [17] with a maximum opening angle of ∆φ ≈ 1 (rad) relative to the backside of a triggered high-p T hadron. However, hadron spectra from the freeze-out of the Mach cone in both hydrodynamics with realistic energy-momentum deposition by jets [6,9,10] and string calculations in the hydrodynamic regime [14] fail to reproduce the observed conic azimuthal correlations. Such correlations on the other hand are observed in a multiphase transport (AMPT) Monte Carlo simulations [18] which could come from jetinduced wakes that are deflected by a radially expanding medium [10].Dihadrons with a high-p T trigger are mostly dominated by b2b jets that are produced close to the surface of the dense matter [19] with the awayside jets often traveling against or tangential to the radial flow. Deflection of these jet showers and associated Mach cones by the radial flow can lead to double-peaked hadron azimuthal correlations. On the other hand, high-p T γ's are produced throughout the volume of the dense matter [20]. The effect of deflection should be reduced for γ-triggered jet showers after averaging over all possible production positions and propagation direction, leading to a weaker double-hump γ-hadron correlation as compared to dihadron correlation.In this Letter, we will study medium excitation by a...

Multistage Monte Carlo simulation of jet modification in a static medium

“…(6) and (8). The only parameter in this LBT model is the strong coupling constant α s that quantifies the jet-medium interaction, which is determined by comparing model calculation to experimental data of single heavy and light flavor hadron production, single inclusive jet production and γ-jet production in heavy-ion collisions [31][32][33][34]51].…”

Operator definition and derivation of collisional energy and momentum loss in relativistic plasmas

“…Many significant attempts have been made to understand the energy momentum deposition (i.e. source term) profile in QCD [31][32][33]. In the strongly-coupled limit, the AdS/CFT correspondence has been used to evaluate the stress-tensor within the context of linearized gravity [34][35][36].…”

Effects of triangular flow on di-hadron azimuthal correlations in relativistic heavy ion collisions

“…Moreover, the away-side double peaks change into a single peak after the subtraction of background correlations due to both hadron elliptic and triangular flows. Although other effects [14][15][16][17][18][19][20][21][22][23][24] on di-hadron correlations are appreciable in central collisions, the away-side double peaks may be dominated by the triangular flow in mid-central collisions.…”

“…It was found in these studies that for central and mid-central collisions of heavy nuclei, there existed not only a pronounced peak at the near side of trigger jets but also a broad double-peak structure at their away side [12,13]. Different mechanisms have been proposed to explain this interesting phenomenon, including the medium-induced gluon radiation [14,15], the Mach cone from the shock wave generated by the traversing jet in produced QGP [16,17], the path-length-dependent jet energy loss [18,19], the Cerenkov radiation from the jet [20], the strong parton cascade [21], and the deflection of jets by partons in the QGP [22][23][24]. Also, it was recently pointed out that the so far overlooked large triangular flow, resulting from the non-vanishing triangularity in the initial collision geometry as a result of the spatial fluctuation of participating nucleons [25][26][27], could be responsible for the double-peak structure at the away side of di-hadron correlations [28,29].…”