Charged hadron spectra and dijet $p_{\mathrm{T}}$ correlations measured in Xe+Xe collisions at $\sqrt{s_{_\text{NN}}}=5.44$TeV with the ATLAS detector

The Large Hadron Collider recorded 3$\mu$b${}^{-1}$ of Xe+Xe data in 2017 at a nucleon-nucleon centre-of-mass energy of $\sqrt{s_{_\text{NN}}} = 5.44$TeV. To probe the physics of "jet quenching" in heavy-ion collisions with nuclei lighter than lead, measurements using these data are presented, namely the transverse momentum asymmetry of dijet pairs and the rates for production of charged particles. The dijet transverse momentum imbalance is characterized by the ratio of sub-leading to leading jet transverse momenta, $x_{\mathrm{J}} = p_{\mathrm{T_2}}/ p_{\mathrm{T_1}}$. Distributions of $x_{\mathrm{J}}$ are measured using dijet pairs having $p_{\mathrm{T_1}} > 100$GeV and are not unfolded to the particle level. A centrality-dependent modification relative to $\sqrt{s} = 5.02$TeV $pp$ collisions is observed. It is consistent with that measured in 5.02TeV Pb+Pb collisions, either when compared in the same centrality interval, or when compared using common intervals of forward calorimeter transverse energy. Charged particle per-event yields are measured as a function of transverse momentum in different intervals of Xe+Xe collision centrality and compared to $pp$ charged-particle cross-sections measured at $\sqrt{s}=5.02$TeV, extrapolated to 5.44TeV. Nuclear modification factors, $R_{\mathrm{AA}}$, obtained from the Xe+Xe and $pp$ data show a centrality-dependent suppression of the charged-particle yield with characteristics qualitatively similar to that observed in Pb+Pb collisions.