Constraints on the path-length dependence of jet quenching in nuclear collisions at RHIC and LHC

Betz, Barbara; Gyulassy, Miklós

doi:10.1007/jhep08(2014)090

Cited by 39 publications

(37 citation statements)

References 62 publications

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“…In this work, we will put forward a phenomenological approach which combines different physics mechanisms at different scales. While there have been other attempts to combine results obtained from weak and strong coupling [28][29][30][31], our approach is distinct since it focusses on using different calculational frameworks at the different energy scales.…”

Section: Jhep09(2015)175mentioning

confidence: 99%

“…And, as they describe single partons, they cannot address the question of how the propagation through the strongly coupled plasma does or does not modify the jet fragmentation function, a question that we shall find plays a significant role in differentiating between energy loss mechanisms. Furthermore, in some cases [29,31,49] the rate of energy loss of a hard parton is assumed to be a power law in the parton energy and the propagation distance, whereas we now know from ref. [45] that this is true only for partons which do not travel a significant fraction of their stopping distance, as for those and only those partons dE/dx ∝ E 0 in x 2 .…”

Section: Comparison With Other Approachesmentioning

confidence: 99%

See 1 more Smart Citation

Erratum to: A hybrid strong/weak coupling approach to jet quenching

Casalderrey-Solana

Gulhan

Milhano

et al. 2015

J. High Energ. Phys.

101

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Erratum to: JHEP10(2014)019ArXiv ePrint: 1405.3864After the publication of this work we have found a small mistake in our implementation of the Glauber Monte-Carlo for the collision geometry, which resulted in an incorrect distribution of the points in the transverse plane at which our jets were created, for collisions within each centrality bin. After correcting this, the fitted values of κ sc , κ rad and κ coll in the current version of this paper are slightly smaller than previously reported. This correction also results in small (hardly visible) changes to all the plots in this paper, which we have corrected. Neither the changes to the fitted values of the κ's nor the changes to the figures affect any discussion or any conclusions of this work; we have made no changes to the wording in any discussion of any figure or result. We have also reduced the p T -cut of our PYTHIA simulations from 70 GeV to 50 GeV to further reduce the sensitivity of our computations to this cut.Open Access, c The Authors. Article funded by SCOAP 3 .doi:10.1007/JHEP09(2015)175 JHEP09(2015)175Abstract: We propose and explore a new hybrid approach to jet quenching in a strongly coupled medium. The basis of this phenomenological approach is to treat physics processes at different energy scales differently. The high-Q 2 processes associated with the QCD evolution of the jet from its production as a single hard parton through its fragmentation, up to but not including hadronization, are treated perturbatively following DGLAP evolution, to which we ascribe a spacetime structure. The interactions between the partons in the shower and the deconfined matter within which they find themselves lead to energy loss. The momentum scales associated with the medium itself (of the order of the temperature) and with typical interactions between partons in the shower and the medium are sufficiently soft that strongly coupled physics plays an important role in energy loss. We model these interactions using qualitative insights inferred from holographic calculations of the energy loss of energetic light quarks and gluons in a strongly coupled plasma, obtained via gauge/gravity duality. We embed this hybrid model into a hydrodynamic description of the spacetime evolution of the hot QCD matter produced in heavy ion collisions and confront its predictions with experimental results for a number of observables that have been measured in high energy jet data from heavy ion collisions at the LHC, including jet R AA as a function of transverse momentum, the dijet asymmetry, and the jet fragmentation function ratio, all as functions of collision centrality. The holographic expression for the energy loss of a light quark or gluon that we incorporate in our hybrid model is parametrized by a stopping distance. We find very good agreement with all the data as long as we choose a stopping distance that is comparable to but somewhat longer than that in N = 4 supersymmetric Yang-Mills theory. For comparison, we also construct analogous alternative models in which we assu...

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Section: Jhep09(2015)175mentioning

confidence: 99%

Section: Comparison With Other Approachesmentioning

confidence: 99%

Erratum to: A hybrid strong/weak coupling approach to jet quenching

Casalderrey-Solana

Gulhan

Milhano

et al. 2015

J. High Energ. Phys.

101

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“…Such studies have been performed at RHIC [18] and at the LHC [19][20][21] up to p T ≈ 10 and 60 GeV/c, respectively. Most jet quenching models are unable to simultaneously reproduce the R AA and v 2 measurements [22][23][24]. Nevertheless, recent attempts to solve this puzzle have shown promise by considering initial-state collision geometry asymmetries and fluctuations [25,26], which are predicted to strongly affect the high-p T v n coefficients, but not the R AA values.…”

Section: Introductionmentioning

confidence: 99%

Azimuthal anisotropy of charged particles with transverse momentum up to 100 GeV/c in PbPb collisions at sNN=5.02 TeV

Sirunyan¹,

Tumasyan²,

Adam³

et al. 2018

Physics Letters B

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The Fourier coefficients v 2 and v 3 characterizing the anisotropy of the azimuthal distribution of charged particles produced in PbPb collisions at √ s NN = 5.02 TeV are measured with data collected by the CMS experiment. The measurements cover a broad transverse momentum range, 1 < p T < 100 GeV/c. The analysis focuses on the p T > 10 GeV/c range, where anisotropic azimuthal distributions should reflect the path-length dependence of parton energy loss in the created medium. Results are presented in several bins of PbPb collision centrality, spanning the 60% most central events. The v 2 coefficient is measured with the scalar product and the multiparticle cumulant methods, which have different sensitivities to initial-state fluctuations. The values from both methods remain positive up to p T ∼ 60-80 GeV/c, in all examined centrality classes. The v 3 coefficient, only measured with the scalar product method, tends to zero for p T 20 GeV/c. Comparisons between theoretical calculations and data provide new constraints on the path-length dependence of parton energy loss in heavy ion collisions and highlight the importance of the initial-state fluctuations.The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter providing a 3.8 T field. Within the solenoid volume there are a silicon pixel and strip tracker detector, a lead tungstate crystal electromagnetic calorimeter (ECAL), and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections. Muons are measured in gas-ionization detectors embedded in the steel flux-return yoke outside the solenoid. The silicon tracker measures charged particles within |η| < 2.5 and provides a p T resolution of about 1.5% for 100 GeV charged particles. Furthermore, the track impact parameter resolution is about 25-90 (45-150) µm in the transverse (longitudinal) dimension, depending on η and p T [31]. Iron and quartz-fiber Cherenkov hadron forward (HF) calorimeters cover the range 2.9 < |η| < 5.2 on either side of the interaction region. The granularity of the HF towers is ∆η×∆φ = 0.175×0.175 radians, allowing an accurate reconstruction of the heavy ion event plane. A more detailed description of the CMS detector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in Ref. [32]. The detailed Monte Carlo simulation of the CMS detector response is based on GEANT4 [33].

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“…Parton energy loss depends on the density of the medium. The exact form of this dependence is not known yet [34,35].…”

Section: Description Of the Modelmentioning

confidence: 96%

Anisotropic flow of the fireball fed by hard partons

Schulc

Tomášik

2014

Phys. Rev. C

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In nuclear collisions at highest accessible LHC energies, often more than one dijet pairs deposit momentum into the deconfined expanding medium. With the help of 3+1 dimensional relativistic hydrodynamic simulation we show that this leads to measurable contribution to the anisotropy of collective transverse expansion. Hard partons generate streams in plasma which merge if they come close to each other. This mechanism correlates the resulting contribution to flow anisotropy with the fireball geometry and causes an increase of the elliptic flow in non-central collisions.Comment: 5 pages, 4 figures, revised version according to referee's comments - only minor changes and some explanations adde

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Constraints on the path-length dependence of jet quenching in nuclear collisions at RHIC and LHC

Cited by 39 publications

References 62 publications

Erratum to: A hybrid strong/weak coupling approach to jet quenching

Erratum to: A hybrid strong/weak coupling approach to jet quenching

Azimuthal anisotropy of charged particles with transverse momentum up to 100 GeV/c in PbPb collisions at sNN=5.02 TeV

Anisotropic flow of the fireball fed by hard partons

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