Probing subnucleon scale fluctuations in ultraperipheral heavy ion collisions

We show that introducing subnucleon scale fluctuations constrained by HERA diffractive $J/\Psi$ production data significantly affects the incoherent diffractive $J/\Psi$ production cross section in ultraperipheral heavy ion collisions. We find that the inclusion of the additional fluctuations increases the ratio of the incoherent to the coherent cross section approximately by a factor of $2$, and modifies the transverse momentum spectra of the produced $J/\Psi$ at momenta larger than the scale that corresponds to the distance scale of the subnucleonic fluctuations. We present predictions for $J/\Psi$ production in ultraperipheral heavy ion collisions at $\sqrt{s_{NN}}=5.02\,{\rm TeV}$ at the LHC and $200\,{\rm GeV}$ at RHIC.Comment: 9 pages, 8 figures. v2: small clarifications to the text, matches the published versio

Dijet asymmetry at the Large Hadron Collider

The MARTINI numerical simulation allows for direct comparison of theoretical model calculations and the latest results for dijet asymmetry from the ATLAS and CMS collaborations. In this paper, partons are simulated as undergoing radiative and collisional processes throughout the evolution of central lead-lead collisions at the Large Hadron Collider. Using hydrodynamical background evolution determined by a simulation which fits well with the data on charged particle multiplicities from ALICE and a value of $\alpha_s\approx 0.25-0.3$, the dijet asymmetry is found to be consistent with partonic energy loss in a hot, strongly-interacting medium.Comment: 8 pages, 3 figures. For version 2: ATLAS' latest analysis is included, with some comments and minor changes of wordin

Azimuthal anisotropies in p+Pb collisions from classical Yang-Mills dynamics

We compute single and double inclusive gluon distributions in classical Yang-Mills simulations of proton-lead collisions and extract the associated transverse momentum dependent Fourier harmonics $v_2(p_T)$ and $v_3(p_T)$. Gluons have a large $v_2$ in the initial state, while odd harmonics such as $v_3$ vanish identically at the initial time $\tau=0^{+}$. By the time $\tau \lesssim 0.4\,{\rm fm/c}$ final state effects in the classical Yang-Mills evolution generate a non-zero $v_{3}$ and only mildly modify the gluon $v_{2}$. Unlike hydrodynamic flow, these momentum space anisotropies are uncorrelated with the global spatial anisotropy of the collision. A principal ingredient for the generation of $v_2$ and $v_3$ in this framework is the event-by-event breaking of rotational invariance in domains the size of the inverse of the saturation scale $Q_s$. In contrast to our findings in p+Pb collisions Yang-Mills simulations of lead-lead collisions generate much smaller values of $v_{2,3} (p_T)$ and additional collective flow effects are needed to explain experimental data. This is because the locally generated anisotropy due to the breaking of rotational invariance is depleted with the increase in the number of uncorrelated domains.Comment: Minor modifications; Version to appear in Phys. Lett.