CMS Publications#CMSPAS: Event activity dependence of relative Y(nS) production in pPb collisions at 8.16 TeV (CMS-PAS-HIN-25-005) https://cds.cern.ch/record/2961526 #HeavyIons
#CMSPAS: Measurements of Lambda hyperon spin correlations in proton-proton and proton-lead collisions (CMS-PAS-HIN-26-002) https://cds.cern.ch/record/2961524 #HeavyIons
#CMSpaper: Measurement of the top quark pair production cross section in PbPb collisions at√(s_NN) = 5.36 TeV (arXiv:2604.27091) https://arxiv.org/abs/2604.27091 #HeavyIons
Measurement of the top quark pair production cross section in PbPb collisions at $\sqrt{s_\mathrm{NN}}$ = 5.36 TeV
The inclusive cross section for top quark pair ($\mathrm{t\bar{t}}$) production in lead-lead (PbPb) collisions is reported for the first time at a center-of-mass energy per nucleon pair of 5.36 TeV. The analysis uses data corresponding to an integrated luminosity of 1.58 nb$^{-1}$ collected by the CMS experiment at the CERN LHC in 2023. The $\mathrm{t\bar{t}}$ production cross section, $σ_{\mathrm{t\bar{t}}} $ = 3.42$^{+0.54}_{-0.51}$(stat)$^{+0.50}_{-0.43}$(syst) $μ$b, is measured in dilepton final states using a fit to a multivariate discriminator that combines the decay electron and muon kinematic properties with the multiplicity of bottom quark jets. The result is consistent with perturbative quantum chromodynamics calculations at next-to-next-to-leading order (NNLO) accuracy employing several nuclear parton distribution functions. In addition, the Drell$-$Yan production cross section ($σ_\text{DY}$) for dilepton masses above 10 GeV and the ratio of $\mathrm{t\bar{t}}$ to DY cross sections ($R_{\mathrm{t\bar{t}}/\mathrm{DY}}$) are found to be compatible with the NNLO predictions. The observables $σ_{\mathrm{t\bar{t}}}$, $σ_\text{DY}$, and $R_{\mathrm{t\bar{t}}/\mathrm{DY}}$ are measured separately for central and semicentral PbPb collisions to investigate for the first time the dependence of top quark production on the collision impact parameter.
#CMSpaper soon on arXiv: Measurement of the top quark pair production cross section in PbPb collisions at√(s_NN) = 5.36 TeV (CERN-EP-2026-066) https://cds.cern.ch/record/2960484 #HeavyIons
Measurement of the top quark pair production cross section in $ \mathrm{Pb}\mathrm{Pb} $ collisions at$ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}}= $ 5.36 TeV
The inclusive cross section for top quark pair ( $ \mathrm{t} \overline{\mathrm{t}} $) production in lead-lead ($ \mathrm{Pb}\mathrm{Pb} $) collisions is reported for the first time at a center-of-mass energy per nucleon pair of 5.36 TeV. The analysis uses data corresponding to an integrated luminosity of 1.58$ \text{nb}^{-1}$ collected by the CMS experiment at the CERN LHC in 2023. The $ \mathrm{t} \overline{\mathrm{t}} $ production cross section, $ \sigma_{{\mathrm{t}\overline{\mathrm{t}}} }= $ 3.42 $ ^{+0.54}_{-0.51} $ $ $ (stat) $ ^{+0.50}_{-0.43} $ (syst) $\mu b$, is measured in dilepton final states using a fit to a multivariate discriminator that combines the decay electron and muon kinematic properties with the multiplicity of bottom quark jets. The result is consistent with perturbative quantum chromodynamics calculations at next-to-next-to-leading order (NNLO) accuracy employing several nuclear parton distribution functions. In addition, the Drell--Yan production cross section ($ \sigma_\text{DY} $) for dilepton masses above 10 GeV and the ratio of $ \mathrm{t} \overline{\mathrm{t}} $ to DY cross sections ($ R_{{\mathrm{t}\overline{\mathrm{t}}} /\mathrm{DY}} $) are found to be compatible with the NNLO predictions. The observables $ \sigma_{{\mathrm{t}\overline{\mathrm{t}}} } $, $ \sigma_\text{DY} $, and $ R_{{\mathrm{t}\overline{\mathrm{t}}} /\mathrm{DY}} $ are measured separately for central and semicentral $ \mathrm{Pb}\mathrm{Pb} $ collisions to investigate for the first time the dependence of top quark production on the collision impact parameter.
#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}$.