### Conveners

#### Parallel: High pT probes of the initial state

- Brian Cole (Columbia University)

Jets and photons have been studied to constrain the initial and final stages of collisions between two large nuclei at the Large Hadron Collider.

Measurements of photon and jet production $p$+Pb collisions are potentially sensitive to novel effects such as gluon saturation, the onset of non-linear QCD, and the energy loss of partons in the nuclear matter. In A+A collisions jets are modified...

The recent finding of collective behavior of particles emitted in small system collisions calls for reexamination of such systems to determine whether or effects beyond the initial state nuclear effects play a significant role.

High $p_T$ hadrons from jets and direct photons have been powerful probes to explore the dynamics of the heavy ion collisions, since they are produced at the early...

We propose an approach to extract the spatial anisotropy of QGP formed in ultrarelativistic heavy-ion collisions from measured high-pt observables $R_{AA}$ and $v_2$. We show, through analytical arguments, numerical calculations, and comparison with experimental data, that $v_2/(1-R_{AA})$ reaches a well-defined saturation value at high $p_\perp$, which is in turn proportional to the initial...

The ALICE Collaboration studied extensively heavy-flavour production at mid- and forward rapidities in small systems at the LHC. The data provide precise tests for pQCD calculations based on the factorization approach and set constraints to Cold Nuclear-Matter effects that can modify heavy-flavour production in p-Pb collisions with respect to pp collisions. At...

I will present the first calculation of all ${\cal O}(\alpha_s)$ medium-induced branching processes to any order in opacity. The splitting functions results are given as iterative solutions to matrix equations with initial conditions set by the leading order branchings in the vacuum. The flavor and quark mass dependence of the in-medium $q \rightarrow qg$, $g\rightarrow gg$, $q...