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The many different theoretical studies of energy loss of a quark or gluon traversing a medium have one thing in common: the transport coefficient of a gluon in the medium, $hat{q}$, which is defined as the mean 4-momentum transfer$^2$, $left<q^2right>$, by a gluon to the medium per gluon mean free path, $lambda_{rm mfp}$. In the original BDMPSZ formalism, the energy loss of an outgoing parton, $-dE/dx$, per unit length ($x$) of a medium with total length $L$, due to coherent gluon bremsstrahlung, is proportional to the $left< q^2right>$ and takes the form: ${-dE/dx }simeq alpha_s left<{q^2(L)}right>=alpha_s, mu^2, L/lambda_{rm mfp} =alpha_s, hat{q}, L $ , where $mu$, is the mean momentum transfer per collision. Thus, the total energy loss in the medium goes like $L^2$. Additionally, the accumulated momentum$^2$, $left<{k_{perp}^2}right>$, transverse to a gluon traversing a length $L$ in the medium is well approximated by $left<{k_{perp}^2}right>approxleft<{q^2(L)}right>=hat{q}, L$. A simple estimate shows that the $left<{k_{perp}^2}right>approxhat{q},L$ should be observable at RHIC at $sqrt{s_{NN}}=200$ GeV via the broadening of di-hadron azimuthal correlations resulting in an azimuthal width $simsqrt{2}$ larger in Au$+$Au than in $p+p$ collisions . Measurements relevant to this issue will be discussed as well as recent STAR jet results presented at QM2014. Other topics to be discussed include the danger of using forward energy to define centrality in $p(d)+$A collisions for high $p_T$ measurements, the danger of not using comparison $p+p$ data at the same $sqrt{s}$ in the same detector for $R_{AA}$ or lately for $R_{pA}$ measurements.
I will present an overview of identified particle spectra at high $p_T$ ($p_T{}^{>}_{sim}$ 5 GeV/$c$) in both p+p collisions and AA collisions at RHIC. In p+p collisions, summary of particle ratios of K, $eta$, $omega$, $rho$, $phi$, $p$, $bar{p}$, $
We report recent results of high-pt measurements in Pb--Pb collisions at $sqrt{s_{NN}}=2.76$ TeV by the ALICE experiment and discuss the implications in terms of energy loss of energetic partons in the strongly interaction medium formed in the collisions.
Within a multi-phase transport model with string melting scenario, jet transport parameter $hat{q}$ is calculated in Au+Au collisions at $sqrt{s_{NN} } $= 200 GeV and Pb+Pb collisions at $sqrt{s_{NN} } $= 2.76 TeV. The $hat{q}$ increases with the inc
Pre-gauging the cosmological scale factor $a(t)$ does not introduce unphysical degrees of freedom into the exact FLRW classical solution. It seems to lead, however, to a non-dynamical mini superspace. The missing ingredient, a generalised momentum en
In the BDMPSZ model, the energy loss of an outgoing parton in a medium $-dE/dx$ is the transport coefficient $hat{q}$ times $L$ the length traveled. This results in jet quenching, which is well established. However BDMPSZ also predicts an azimuthal b