  The transport coefficient $\hat{q}$ is a leading coefficient that controls
the modification of the hard parton traversing QGP, and hence, responsible for
the suppression of the high transverse momentum (transverse to the beam
direction) charged-hadrons in heavy-ion collisions. In this article, we present
the first unquenched lattice QCD calculation of $\hat{q}$. The calculation is
carried out using (2+1)-flavor of quarks, using the highly improved staggered
quark action (HISQ) and tree-level Symanzik improved gauge action. The
calculation is performed in a wide range of temperatures, ranging from 200 MeV
$<T<$ 800 MeV using MILC code package. We considered a leading-order process
where a hard parton scatters off the glue field of a thermal QCD medium by
exchanging a Glauber gluon (whose transverse momentum is larger than its
longitudinal components). The hard scale associated with the jet parton allows
the coupling of the gluon to that parton to be treated in perturbation theory.
The coupling of the gluon to the medium is treated non-perturbatively. This
non-perturbative part is expressed in terms of a non-local (two-point)
field-strength-field-strength operator product which can be Taylor expanded
after analytic continuation to the deep Euclidean region. Such an expansion
allows us to write $\hat{q}$ in terms of a series of local operators, which are
suppressed by factors of the hard parton energy. The calculated $\hat{q}$ and
its temperature dependence demonstrates reasonable agreement with the
phenomenological extraction carried out by the JET collaboration.

Nuclear Theory;High Energy Physics - Lattice;Nuclear Experiment