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, $R^h_{AA}(p_T>10{\rm GeV/c},\sqrt{s})$, and their azimuthal elliptic asymmetry $v^h_2(p_T>10{\rm GeV/c},\sqrt{s})$ 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 $<\hat{q}>$ 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.
Highlights
With available data on h = π, D, B jet fragments from nuclear collisions at RHIC( s = 0.2
While the factor of ∼ 5 quenching of hard leading hadrons observed in central collisions with RAA ∼ 0.2, was well predicted [17] even with perturbative QCD jet medium coupling, the collective bulk azimuthal flow moments observed at RHIC and LHC appear to require much stronger interactions such as those assumed, e.g., 1In the present study we focus on single hadron observables, and the current CUJET implementation considers energy loss of single partons that are subsequently mapped to hadrons
In [71], we summarized the results of our CUJET3.0 extension of a perturbative QCD (pQCD) based energy loss model CUJET2.0 discussed [38, 72] which integrates local parton energy loss over (2+1)D viscous hydrodynamic flows and and models jet medium interactions via the sQGMP quasi-particle model picture of the chromo structure of the fluid that include specific non-pertubative features related to confinement in the vicinity of Tc
Summary
In the pQCD paradigm, radiative processes dominate the jet-medium interactions for a highly energetic parton. E is the energy of the hard parton in the lab frame, k⊥ (|k⊥| ≤ xEE · Γ(z)) and q⊥ (|q⊥| ≤ 6T (z)E · Γ(z)) is the local transverse momentum of the radiated gluon and the local transverse momentum transfer respectively. In the CUJET2.0 model, Zakharov’s 1-loop pQCD running scheme is used [38, 100, 101] This running is cutoff in the infrared when the strong coupling strength reaches a maximum value αmax for Q ≤ Qmin: αmax αs(Q2) =. Event-averaged smooth profiles are embedded, and the path integrations dτ for jets initially produced at transverse coordinates (x0, φ) are cutoff at dynamical T (z(x0, φ, τ ))|τmax ≡ Tcut = 160 MeV hypersurfaces [38]. CTEQ6M PDF; Peterson FF (1/2πpT )d2σ /dpT dη [mb /GeV2·c3] (1/2πpT )d2σ /dpT dη [mb /GeV2·c3]
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