The surprisingly transparent sQGP at LHC

doi:10.1016/j.nuclphysa.2011.09.018

Nuclear Physics A

Volume 872, Issue 1, December 2011, Pages 265-285

https://doi.org/10.1016/j.nuclphysa.2011.09.018 Get rights and content

Abstract

We present parameter-free predictions of the nuclear modification factor, $R_{A A}^{π} (p_{T}, s)$ , of high $p_{T}$ pions produced in Pb + Pb collisions at ${\sqrt{s}}_{N N} = 2.76$ and 5.5 ATeV based on the WHDG/DGLV (radiative + elastic + geometric fluctuation) jet energy loss model. The initial quark gluon plasma (QGP) density at LHC is constrained from a rigorous statistical analysis of PHENIX/RHIC $π^{0}$ quenching data at ${\sqrt{s}}_{N N} = 0.2 ATeV$ and the charged particle multiplicity at ALICE/LHC at 2.76 ATeV. Our perturbative QCD tomographic theory predicts significant differences between jet quenching at RHIC and LHC energies, which are qualitatively consistent with the $p_{T}$ -dependence and normalization—within the large systematic uncertainty—of the first charged hadron nuclear modification factor, $R_{A A}^{c h}$ , data measured by ALICE. However, our constrained prediction of the central to peripheral pion modification, $R_{c p}^{π} (p_{T})$ , for which large systematic uncertainties associated with unmeasured p + p reference data cancel, is found to be over-quenched relative to the charged hadron ALICE $R_{c p}^{c h}$ data in the range $5 < p_{T} < 20 GeV / c$ . The discrepancy challenges the two most basic jet tomographic assumptions: (1) that the energy loss scales linearly with the initial local comoving QGP density, $ρ_{0}$ , and (2) that $ρ_{0} \propto d N^{c h} (s, C) / d y$ is proportional to the observed global charged particle multiplicity per unit rapidity as a function of $\sqrt{s}$ and centrality class, $C$ . Future LHC identified $(h = π, K, p)$ hadron $R_{A A}^{h}$ data (together with precise p + p, p + Pb, and Z boson and direct photon Pb + Pb control data) are needed to assess if the QGP produced at LHC is indeed less opaque to jets than predicted by constrained extrapolations from RHIC.

References (116)

K. Adcox
Nucl. Phys. A
(2005)
J. Adams
Nucl. Phys. A
(2005)
B.B. Back
Nucl. Phys. A
(2005)
I. Arsene
Nucl. Phys. A
(2005)
M. Gyulassy et al.
Nucl. Phys. A
(2005)
E.V. Shuryak
Nucl. Phys. A
(2005)
S.S. Gubser et al.
Phys. Lett. B
(1998)
S.S. Gubser
Nucl. Phys. A
(2009)
E. Braaten et al.
Nucl. Phys. B
(1990)
J.O. Andersen et al.
Phys. Lett. B
(2011)

K. Aamodt

Phys. Rev. Lett.

(2011)

G. Aad

Phys. Rev. Lett.

JHEP

(2008)

P.M. Chesler et al.

Phys. Rev. D

(2009)

Cited by (107)

Constraining the equation of state with heavy quarks in the quasi-particle model of QCD matter
2024, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
In a quasi-particle model of QCD matter at finite temperature with thermal masses for quarks and gluons from hard thermal loops, the equation of state (EOS) can be described by an effective temperature dependence of the strong coupling $g (T)$ . Assuming the same effective coupling between the exchanged gluon and thermal partons, the EOS can also be related to parton energy loss. Based on the quasi-particle linear Boltzmann transport (QLBT) model coupled to a (3+1)-dimensional viscous hydrodynamic model of the quark-gluon plasma (QGP) evolution and a hybrid fragmentation-coalescence model for heavy quark hadronization, we perform a Bayesian analysis of the experimental data on D meson suppression $R_{AA}$ and anisotropy $v_{2}$ at RHIC and the LHC. We achieve a simultaneous constraint on the QGP EOS and the heavy quark transport coefficient, both consistent with the lattice QCD results.
How does the Quark-Gluon Plasma know the collision energy?
2018, Nuclear Physics B
Citation Excerpt :
This simple observation has many crucial ramifications, as was pointed out by Becattini et al. [4]; inter alia it implies that the densities and temperatures arising in peripheral collisions at sufficiently high impact parameter are arbitrarily lower than those in central collisions. It follows [5–8] that sufficiently peripheral collisions studied [9,10] at the LHC give rise to plasmas having the same energy density and temperature as plasmas produced in central collisions at the RHIC. This opens the way to an investigation of a fundamental question: does the plasma produced in peripheral collisions “know” about global parameters like the overall impact energy, or is it sensitive only to explicitly local parameters such as the energy density?
Heavy ion collisions at the LHC facility generate a Quark-Gluon Plasma (QGP) which, for central collisions, has a higher energy density and temperature than the plasma generated in central collisions at the RHIC. But sufficiently peripheral LHC collisions give rise to plasmas which have the same energy density and temperature as the “central” RHIC plasmas. One might assume that the two versions of the QGP would have very similar properties (for example, with regard to jet quenching), but recent investigations have suggested that they do not: the plasma “knows” that the overall collision energy is different in the two cases. We argue, using a gauge-gravity analysis, that the strong magnetic fields arising in one case (peripheral collisions), but not the other, may be relevant here. If the residual magnetic field in peripheral LHC plasmas is of the order of at least $e B \approx 5 m_{π}^{2}$ , then the model predicts modifications of the relevant quenching parameter which approach those recently reported.
A Unified Description for Comprehensive Sets of Jet Energy Loss Observables with CUJET3
2017, Nuclear Physics A
Jet energy loss in heavy ion collisions, as quantified by the traditional observable of high $p_{T}$ hadron's nuclear modification factor $R_{AA}$ , provides highly informative “imaging” of the hot medium created in heavy ion collisions. There are now comprehensive sets of available data, from average suppression to azimuthal anisotropy, from light to heavy flavors, from RHIC 200GeV to LHC 2.76TeV as well as 5.02TeV collisions. A unified description of such comprehensive data presents a stringent vetting of any viable model for jet quenching phenomenology. In this contribution we report such a systematic and successful test of CUJET3, a jet energy loss simulation framework built upon a nonperturbative microscopic model for the hot medium as a semi-quark-gluon-monopole plasma (sQGMP) which integrates two essential elements of confinement, i.e. the Polyakov-loop suppression of quarks/gluons and emergent magnetic monopoles.
Measurement of the production of high-p<inf>T</inf> electrons from heavy-flavour hadron decays in Pb–Pb collisions at s<inf>NN</inf>=2.76 TeV
2017, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Electrons from heavy-flavour hadron decays (charm and beauty) were measured with the ALICE detector in Pb–Pb collisions at a centre-of-mass of energy $\sqrt{s_{NN}} = 2.76 TeV$ . The transverse momentum ( $p_{T}$ ) differential production yields at mid-rapidity were used to calculate the nuclear modification factor $R_{AA}$ in the interval $3 < p_{T} < 18$ GeV/c. The $R_{AA}$ shows a strong suppression compared to binary scaling of pp collisions at the same energy (up to a factor of 4) in the 10% most central Pb–Pb collisions. There is a centrality trend of suppression, and a weaker suppression (down to a factor of 2) in semi-peripheral (50–80%) collisions is observed. The suppression of electrons in this broad $p_{T}$ interval indicates that both charm and beauty quarks lose energy when they traverse the hot medium formed in Pb–Pb collisions at LHC.
Light quark energy loss at finite ’t Hooft coupling from holography
2024, European Physical Journal Plus
Energy Loss in Small Collision Systems
2024, Proceedings of Science

View all citing articles on Scopus

View full text