CMS Publications#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
#CMSpaper soon on arXiv: System-size dependence of charged-particle suppression in ultrarelativistic nucleus-nucleus collisions (CERN-EP-2026-032) https://cds.cern.ch/record/2955423 #HeavyIons
System-size dependence of charged-particle suppression in ultrarelativistic nucleus-nucleus collisions
High-energy partons lose energy while propagating through the hot, strongly interacting medium produced in ultrarelativistic nucleus-nucleus collisions, leading to a suppression of particle production at high transverse momentum ($ p_{\mathrm{T}} $). The dependence of this energy loss on the size of the colliding nuclear system has yet to be firmly established experimentally. This Letter presents a systematic study of charged-particle suppression across four different nucleus-nucleus collision systems using nuclear modification factors ($ R_{\text{AA}} $) measured by the CMS Collaboration at the CERN LHC. Previous CMS measurements of $ R_{\text{AA}} $ in oxygen-oxygen, xenon-xenon, and lead-lead collisions are recast with identical $ p_{\mathrm{T}} $ intervals and are complemented by the first measurement of the charged-particle $ R_{\text{AA}} $ in neon-neon collisions at $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = $ 5.36 TeV. The neon-neon data correspond to an integrated luminosity of 0.76$ \text{nb}^{-1}$. The $ R_{\text{AA}} $ in all collision systems examined show similar qualitative trends, but have a magnitude which is ordered with the nucleon number $ A $. The $ R_{\text{AA}} $ feature a downward slope at low $ p_{\mathrm{T}} $, a local minimum at around 5-7 GeV, and an upward slope with increasing $ p_{\mathrm{T}} $. The $ R_{\text{AA}} $ are also compared in terms of $ A^{1/3} $, which is proportional to the nuclear radius. Models including only initial-state nuclear effects fail to reproduce the observed trends, whereas energy loss models reproduce the trends in the region $ p_{\mathrm{T}} > $ 9.6 GeV.
#CMSpaper soon on arXiv: Observation of the jet diffusion wake using dijets in heavy ion collisions (CERN-EP-2026-017) 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: First measurement of jet axis decorrelation with photon-tagged jets in pp and PbPb collisions at 5.02 TeV (arXiv:2602.18279) https://arxiv.org/abs/2602.18279 #HeavyIons
#CMSpaper soon on arXiv: First measurement of jet axis decorrelation with photon-tagged jets in pp and PbPb collisions at 5.02 TeV (CERN-EP-2024-331) https://cds.cern.ch/record/2955158 #HeavyIons
First measurement of jet axis decorrelation with photon-tagged jets in pp and $ \mathrm{PbPb} $ collisions at 5.02 TeV
The first measurement of the jet axis decorrelation in events with jets recoiling from an isolated photon is presented for lead-lead ($ \mathrm{PbPb} $) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The jet axis decorrelation is the angular difference ($ \Delta{j} $) between two definitions of the jet axis. This quantity is expected to be sensitive to the scattering of jet constituents in the quark-gluon plasma (QGP). Events which have a leading isolated photon with transverse momentum 60 $ < p_{\mathrm{T}}^{\gamma} < $ 200 GeV and recoiling jets with 30 $ < p_{\mathrm{T}}^{\text{jet}} < $ 100 GeV are selected for the analysis. The $ \mathrm{PbPb} $ result is reported as a function of collision centrality and compared to pp reference data. Jets with $ p_{\mathrm{T}}^{\text{jet}} < $ 60 GeV have consistent $ \Delta{j} $ shapes for pp and $ \mathrm{PbPb} $ collisions. However, a narrowing is observed for jets with $ p_{\mathrm{T}}^{\text{jet}} > $ 60 GeV in central $ \mathrm{PbPb} $ collisions. The results are compared to predictions from the JEWEL, PYQUEN and HYBRID theoretical models, which include different descriptions of parton energy loss in the QGP.
#CMSpaper: Influence of strangeness on the anisotropic flow of prompt D^±_s mesons in PbPb collisions at √(s_NN) = 5.02 TeV (arXiv:2602.14221) https://arxiv.org/abs/2602.14221 #HeavyIons
#CMSpaper soon on arXiv: Influence of strangeness on the anisotropic flow of prompt D^±_s mesons in PbPb collisions at √(s_NN) = 5.02 TeV (CERN-EP-2025-250) https://cds.cern.ch/record/2954794 #HeavyIons
Influence of strangeness on the anisotropic flow of prompt $ \mathrm{D}_{s}^{\pm} $ mesons in PbPb collisions at $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = $ 5.02 TeV
The azimuthal anisotropy of prompt $ \mathrm{D}_{s}^{\pm} $ mesons produced in lead-lead (PbPb) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV is measured using data obtained with the CMS detector. The dataset corresponds to an integrated luminosity of 0.58$ \text{nb}^{-1}$. The azimuthal anisotropy of heavy charmed mesons provides a key constraint on the interactions of charm quarks with the quark-gluon plasma (QGP) medium. These interactions include coalescence mechanisms and parton energy loss in the QGP. The anisotropy is quantified by the second- ($ v_{2} $) and third-order ($ v_{3} $) Fourier coefficients of the azimuthal distribution of the $ \mathrm{D}_{s}^{\pm} $ mesons. The $ v_{2} $ coefficient is determined in the transverse momentum range 4 $ < p_{\mathrm{T}} < $ 40 GeV for three event centrality classes, while the $ v_{3} $ coefficient is measured in the range 4 $ < p_{\mathrm{T}} < $ 20 GeV for a single event centrality class. The results for the $ \mathrm{D}_{s}^{\pm} $ mesons are compared to those previously measured for $ \mathrm{D^0} $ mesons. The azimuthal anisotropy coefficients for $ \mathrm{D}_{s}^{\pm} $ and $ \mathrm{D^0} $ mesons are found to be consistent within the precision of this measurement, suggesting that the strangeness content of the $ \mathrm{D}_{s}^{\pm} $ meson does not significantly alter its azimuthal distribution within the measured $ p_{\mathrm{T}} $ range.
#CMSpaper: Probing early parton emissions in heavy ion collisions using the Lund jet plane (arXiv:2602.09271) https://arxiv.org/abs/2602.09271 #HeavyIons