First measurement of dNch/dη in OO collisions at 5.36 TeV yields midrapidity densities of 41.8 overall and 135 in central events, consistent with PbPb per participant but showing deviations from simple scaling.
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STARlight: A Monte Carlo simulation program for ultra-peripheral collisions of relativistic ions
Tool reference. 80% of classified Pith citations use this work as a method, library, or software dependency, not as a substantive claim.
abstract
Ultra-peripheral collisions (UPCs) have been a significant source of study at RHIC and the LHC. In these collisions, the two colliding nuclei interact electromagnetically, via two-photon or photonuclear interactions, but not hadronically; they effectively miss each other. Photonuclear interactions produce vector meson states or more general photonuclear final states, while two-photon interactions can produce lepton or meson pairs, or single mesons. In these interactions, the collision geometry plays a major role. We present a program, STARlight, that calculates the cross-sections for a variety of UPC final states and also creates, via Monte Carlo simulation, events for use in determining detector efficiency.
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representative citing papers
First measurement of the nuclear modification factor R_AA in OO collisions at 5.36 TeV shows suppression with a minimum of 0.69 at p_T around 6 GeV, favoring models with parton energy loss.
First differential cross-sections for γγ→ττ in Pb+Pb collisions yield 95% CL intervals -0.057 < a_τ < 0.035 and |d_τ| < 2.7×10^{-16} e cm.
First measurement of γ+IP→jets cross-sections in 0n0n ultra-peripheral Pb+Pb collisions at 5.02 TeV, achieved by statistically separating photon-pomeron, photon-photon, and peripheral photonuclear contributions via template fits to minimum rapidity gap distributions.
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ATLAS reports differential cross sections for coherent exclusive J/ψ → μ⁺μ⁻ in Pb+Pb ultraperipheral collisions at √s_NN=5.36 TeV, agreeing with models but in tension with prior Run 2 data at central rapidity.
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ATLAS reports on its Run 3 software infrastructure for data management, workflows, databases, validation, and physics analysis tools at the LHC.
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Observation of impact parameter dependent modifications of nuclear parton distributions in photonuclear Pb+Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV with the ATLAS detector
ATLAS reports a 6 sigma observation that nuclear parton distribution modifications in photonuclear Pb+Pb collisions depend on impact parameter, shown by differing cross-section shapes versus x+ with and without forward neutron emission.