[Paper Review] Robustness and Consistency of Jet Quenching and Perfect Fluidity in semi Quark Gluon Monopole Plasmas (sQGMP) Produced at RHIC and LHC

Jiechen Xu, Jinfeng Liao+1 more|arXiv (Cornell University)|Aug 3, 2015

High-Energy Particle Collisions Research2 citations

TL;DR

This paper proposes CUJET3.0, a new jet quenching model that incorporates non-perturbative effects from the QCD confinement crossover near Tc ≈ 160 MeV, including suppression of quark/gluon degrees of freedom and emergence of chromo-magnetic monopoles in a semi-Quark-Gluon-Monopole Plasma (sQGMP). It resolves the long-standing RAA vs v2 puzzle by predicting a peak in the jet quenching parameter  ̂q(E,T)/T³ near Tc and demonstrates consistency between jet quenching and perfect fluidity via η/s ≈ 1/4π in the (1–2)Tc range.

ABSTRACT

A new model of jet quenching in nuclear collisions, CUJET3.0, is constructed by generalizing the perturbative QCD based CUJET2.0 model to include two complementary non-perturbative features of the QCD confinement cross-over phase transition near $T_c\approx 160$ MeV: (1) the suppression of quark and gluon degrees of freedom and (2) the emergence of chromo-magnetic monopole degrees of freedom. Such a semi-Quark-Gluon-Monopole Plasma (sQGMP) microscopic scenario is tested by comparing predictions of the leading hadron nuclear modification factors, $R^h_{AA}(p_T>10{ m GeV/c},\sqrt{s})$, and their azimuthal elliptic asymmetry $v^h_2(p_T>10{ m GeV/c},\sqrt{s})$ with available data on $h=\pi,D,B$ jet fragments from nuclear collisions at RHIC($\sqrt{s}=0.2$ ATeV) and LHC($\sqrt{s}$=2.76 ATeV). The sQGMP model is shown to solve the long standing $R_{AA}$ vs $v_2$ puzzle by predicting a maximum of the jet quenching parameter field $\hat{q}(E,T)/T^3$ near $T_c$. The consistency of jet quenching with observed bulk perfect fluidity is demonstrated by extrapolating the sQGMP $\hat{q}$ down to thermal energy $E\sim 3 T$ scales and showing that the sQGMP shear viscosity to entropy density ratio $\eta/s \approx T^3/\hat{q}$ falls close to the unitarity bound, $1/4\pi$, in the range $(1-2)T_c$. Detailed comparisons of CUJET2.0 and CUJET3.0 reveal that the remarkably different $\hat{q}(T)$ could be consistent with the same $R_{AA}$ data and could only be distinguished by anisotropy observables. These findings demonstrate clearly the inadequacy of focusing on the jet path averaged quantity $ $ as the only relevant medium property to characterize jet quenching, and point to the crucial roles of other essential factors, such as the chromo electric and magnetic composites of the plasma, the screening masses and the running couplings at multiple scales that all strongly influence jet energy loss.

Motivation & Objective

• To address the long-standing inconsistency between nuclear modification factor RAA and elliptic flow v2 in jet quenching data from RHIC and LHC.
• To incorporate non-perturbative features of the QCD confinement crossover near Tc ≈ 160 MeV into jet quenching models.
• To test whether the emergence of chromo-magnetic monopoles in a semi-Quark-Gluon-Monopole Plasma (sQGMP) can reconcile jet quenching with observed bulk perfect fluidity.
• To demonstrate that jet quenching and bulk viscosity are consistently described by a single microscopic plasma model.

Proposed method

• Generalize the perturbative QCD-based CUJET2.0 model to include non-perturbative effects from the QCD confinement crossover near Tc ≈ 160 MeV.
• Introduce two key features: suppression of quark and gluon degrees of freedom and the emergence of chromo-magnetic monopole degrees of freedom in the sQGMP state.
• Construct the sQGMP model by embedding these non-perturbative effects into the jet quenching framework to compute the jet quenching parameter  ̂q(E,T).
• Compare predictions of leading hadron RAA and v2 for π, D, and B mesons at RHIC and LHC energies with experimental data.
• Extrapolate the sQGMP  ̂q down to low energy scales (E ~ 3T) to compute the shear viscosity to entropy density ratio η/s ≈ T³/ ̂q.
• Use anisotropy observables (v2) to distinguish between CUJET2.0 and CUJET3.0 despite similar RAA fits.

Experimental results

Research questions

• RQ1 Can the inclusion of non-perturbative chromo-magnetic monopole degrees of freedom in a semi-Quark-Gluon-Monopole Plasma resolve the RAA vs v2 puzzle in jet quenching?
• RQ2 Does the jet quenching parameter  ̂q(E,T)/T³ peak near the QCD crossover temperature Tc ≈ 160 MeV in the sQGMP model?
• RQ3 Is the shear viscosity to entropy density ratio η/s in the sQGMP model consistent with the unitarity bound 1/4π near (1–2)Tc?
• RQ4 Can the same RAA data be consistently described by both CUJET2.0 and CUJET3.0, with the distinction revealed only through anisotropy observables?
• RQ5 Do chromo-electric and magnetic composites, screening masses, and running couplings at multiple scales significantly influence jet energy loss beyond the path-averaged  ̂q?

Key findings

• The sQGMP model predicts a maximum in the jet quenching parameter  ̂q(E,T)/T³ near the QCD crossover temperature Tc ≈ 160 MeV, resolving the RAA vs v2 puzzle.
• The sQGMP model achieves consistency between jet quenching and perfect fluidity, with η/s ≈ T³/ ̂q falling close to the unitarity bound 1/4π in the temperature range (1–2)Tc.
• Despite similar fits to RAA data, CUJET2.0 and CUJET3.0 predict remarkably different  ̂q(T) behaviors, distinguishable only through anisotropy observables like v2.
• The model demonstrates that focusing solely on the path-averaged  ̂q is inadequate for characterizing jet quenching, as chromo-magnetic composites, screening masses, and running couplings at multiple scales play crucial roles.
• The inclusion of non-perturbative features—quark/gluon suppression and chromo-magnetic monopoles—leads to a more consistent and physically complete description of jet quenching and bulk hydrodynamics.
• The sQGMP framework provides a unified microscopic explanation linking jet quenching and perfect fluidity in heavy-ion collisions at RHIC and LHC.