CMS Publications#CMSPAS: Evidence for sequential Upsilon suppression in light ion collisions (CMS-PAS-HIN-25-015) https://cds.cern.ch/record/2959202 #HeavyIons
#CMSpaper: Observation of nuclear suppression in coherent Υ(1S) photoproduction off heavy nuclei at the LHC (arXiv:2604.05814) https://arxiv.org/abs/2604.05814 #HeavyIons
#CMSpaper: Observation of nuclear suppression in coherent Υ(1S) photoproduction off heavy nuclei at the LHC (CMS-HIN-24-013) https://cds.cern.ch/record/2958513 #HeavyIons
Observation of nuclear suppression in coherent $ \Upsilon{\textrm{(1S)}} $ photoproduction off heavy nuclei at the LHC
The first measurement of coherent $ \Upsilon{\textrm{(1S)}} $ meson photoproduction off heavy nuclei is performed using ultraperipheral lead-lead collisions collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The nuclear gluonic structure is probed at a nucleon momentum fraction of order $ x{\sim}10^{-3} $, determined by the kinematics of the process. Owing to the large $ \Upsilon{\textrm{(1S)}} $ mass, the measurement reaches the highest scale accessible so far through coherent vector-meson photoproduction, $ \mu^2 = 22.4 \text{GeV}^2 $, where nonlinear quantum chromodynamics effects are expected to be minimal. In the $ \Upsilon{\textrm{(1S)}} $ rapidity range $ |y| < $ 1, the ratio of the measured photoproduction cross section to a baseline model prediction that neglects nuclear effects is $ S_{\Upsilon{\textrm{(1S)}}}= $ 0.25 $ \pm $ 0.06 (stat) $ \pm $ 0.02 (syst), thereby demonstrating nuclear suppression in this process. Expressed in terms of a nuclear gluon suppression factor, the result yields $ R^{\mathrm{Pb}}_{\mathrm{g}}(x\approx10^{-3},\mu^2=22.4 \text{GeV}^2)= $ 0.55 $ \pm $ 0.12 (stat) $ \pm $ 0.02 (syst). The measured $ R^{\mathrm{Pb}}_{\mathrm{g}} $ is only slightly larger than the values previously reported for coherent $ \phi $ photoproduction, despite the probed $ \mu^2 $ differing by approximately two orders of magnitude.
#CMSpaper soon on arXiv: Observation of nuclear suppression in coherent Υ(1S) photoproduction off heavy nuclei at the LHC (CERN-EP-2026-050) https://cds.cern.ch/record/2958513 #HeavyIons
Observation of nuclear suppression in coherent $ \Upsilon{\textrm{(1S)}} $ photoproduction off heavy nuclei at the LHC
The first measurement of coherent $ \Upsilon{\textrm{(1S)}} $ meson photoproduction off heavy nuclei is performed using ultraperipheral lead-lead collisions collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The nuclear gluonic structure is probed at a nucleon momentum fraction of order $ x{\sim}10^{-3} $, determined by the kinematics of the process. Owing to the large $ \Upsilon{\textrm{(1S)}} $ mass, the measurement reaches the highest scale accessible so far through coherent vector-meson photoproduction, $ \mu^2 = 22.4 \text{GeV}^2 $, where nonlinear quantum chromodynamics effects are expected to be minimal. In the $ \Upsilon{\textrm{(1S)}} $ rapidity range $ |y| < $ 1, the ratio of the measured photoproduction cross section to a baseline model prediction that neglects nuclear effects is $ S_{\Upsilon{\textrm{(1S)}}}= $ 0.25 $ \pm $ 0.06 (stat) $ \pm $ 0.02 (syst), thereby demonstrating nuclear suppression in this process. Expressed in terms of a nuclear gluon suppression factor, the result yields $ R^{\mathrm{Pb}}_{\mathrm{g}}(x\approx10^{-3},\mu^2=22.4 \text{GeV}^2)= $ 0.55 $ \pm $ 0.12 (stat) $ \pm $ 0.02 (syst). The measured $ R^{\mathrm{Pb}}_{\mathrm{g}} $ is only slightly larger than the values previously reported for coherent $ \phi $ photoproduction, despite the probed $ \mu^2 $ differing by approximately two orders of magnitude.
#CMSpaper: Jet peak shapes based on two-particle angular correlations in lead-lead collisions at √(s_NN) = 5.02 TeV (arXiv:2603.14385) https://arxiv.org/abs/2603.14385 #HeavyIons
Jet peak shapes based on two-particle angular correlations in lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
The longitudinal invariance of jet-induced peaks in two-particle correlation functions from relativistic lead-lead collisions is experimentally explored. The data were collected at a center-of-mass energy per nucleon pair of 5.02 TeV in 2018 using the CMS detector. The dataset corresponds to an integrated luminosity of 0.607 nb$^{-1}$. Long- and short-range correlations are studied through two-dimensional distributions of the separations in pseudorapidity and azimuth between particles in an event. Jets manifest as a well-defined peak at small angular separations, and the shape of this peak provides insight into jet medium interactions. This Letter examines the evolution of the jet peak shape, focusing on the dependence of its width and longitudinal asymmetry on the transverse momentum, collision centrality, and pseudorapidity of the associated charged particles. The jet-peak distributions of lower transverse momentum particles broaden in both pseudorapidity and azimuth with increasing collision overlap, with the broadening in pseudorapidity being more pronounced. The longitudinal asymmetry of the peaks is also found to increase as the average pseudorapidity increases. These results are compared to proton-proton collision data that were obtained at the same nucleon-nucleon collision center-of-mass energy with an integrated luminosity of 252 nb$^{-1}$.
#CMSpaper soon on arXiv: Jet peak shapes based on two-particle angular correlations in lead-lead collisions at √(s_NN) = 5.02 TeV (CERN-EP-2025-112) https://cds.cern.ch/record/2957508 #HeavyIons
Jet peak shapes based on two-particle angular correlations in lead-lead collisions at $ \sqrt{{s_{_{\mathrm{NN}}}}} = $ 5.02 TeV
The longitudinal invariance of jet-induced peaks in two-particle correlation functions from relativistic lead-lead collisions is experimentally explored. The data were collected at a center-of-mass energy per nucleon pair of 5.02 TeV in 2018 using the CMS detector. The dataset corresponds to an integrated luminosity of 0.607$ \text{nb}^{-1}$. Long- and short-range correlations are studied through two-dimensional distributions of the separations in pseudorapidity and azimuth between particles in an event. Jets manifest as a well-defined peak at small angular separations, and the shape of this peak provides insight into jet medium interactions. This Letter examines the evolution of the jet peak shape, focusing on the dependence of its width and longitudinal asymmetry on the transverse momentum, collision centrality, and pseudorapidity of the associated charged particles. The jet-peak distributions of lower transverse momentum particles broaden in both pseudorapidity and azimuth with increasing collision overlap, with the broadening in pseudorapidity being more pronounced. The longitudinal asymmetry of the peaks is also found to increase as the average pseudorapidity increases. These results are compared to proton-proton collision data that were obtained at the same nucleon-nucleon collision center-of-mass energy with an integrated luminosity of 252$ \text{nb}^{-1}$.
#CMSPAS: Spin-dependent azimuthal asymmetry of coherent J/ψ photoproduction in peripheral PbPb collisions at √(s_NN) = 5.36 TeV (CMS-PAS-HIN-25-006) https://cds.cern.ch/record/2957192 #HeavyIons
#CMSpaper: Observation of the jet diffusion wake using dijets in heavy ion collisions (arXiv:2602.19431) https://arxiv.org/abs/2602.19431 #HeavyIons
#CMSpaper: Observation of the jet diffusion wake using dijets in heavy ion collisions (CMS-HIN-25-012) https://cds.cern.ch/record/2955422 #HeavyIons
Observation of the jet diffusion wake using dijets in heavy ion collisions
Energetic quarks and gluons traversing a hot and dense quark-gluon plasma deposit energy and momentum into the medium before hadronizing to collimated sprays of particles, known as jets. This energy-momentum deposition is expected to produce medium responses, collectively known as jet wakes, with ``diffusion wake'' denoting a depletion of particles in the direction opposite to the propagating jet. These phenomena are studied by comparing dijet-hadron correlations measured in lead-lead (PbPb) and proton-proton ($ \text{pp} $) collisions to assess jet-induced modifications of bulk particle production. The analysis uses PbPb and $ \text{pp} $ data recorded at a nucleon-nucleon center-of-mass energy $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = $ 5.02 TeV with the CMS detector at the CERN LHC. By exploring how the dijet-hadron correlation distributions differ for various pseudorapidity separations of the two jets in the dijet, the presence of a jet diffusion wake is firmly established. The wake has a significance greater than 5 standard deviations for charged particles in the transverse momentum range 1 $ < p_{\mathrm{T}} < $ 2 GeV. The measurements are compared with various model predictions with and without jet wake effects, providing new insights into quark-gluon plasma properties and the formation of jet-induced wakes.
#CMSpaper: System-size dependence of charged-particle suppression in ultrarelativistic nucleus-nucleus collisions (arXiv:2602.21325) https://arxiv.org/abs/2602.21325 #HeavyIons