555 research outputs found

    SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

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    Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population

    New Structures in the J/ψJ/ψ Mass Spectrum in Proton-Proton Collisions at s\sqrt{s}=13 TeV

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    New Structures in the J/ψJ/ψ Mass Spectrum in Proton-Proton Collisions at s\sqrt{s}=13 TeV

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    Search for jet quenching with dijets from high-multiplicity pPb collisions at sNN= \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = 8.16 TeV

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    The first measurement of the dijet transverse momentum balance xj x_{j} in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of sNN= \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = 8.16 TeV is presented. The xj x_{j} observable, defined as the ratio of the subleading over leading jet transverse momentum in a dijet pair, is used to search for jet quenching effects. The data, corresponding to an integrated luminosity of 174.6 nb1^{-1}, were collected with the CMS detector in 2016. The xj x_{j} distributions and their average values are studied as functions of the charged-particle multiplicity of the events and for various dijet rapidity selections. The latter enables probing hard scattering of partons carrying distinct nucleon momentum fractions x x in the proton- and lead-going directions. The former, aided by the high-multiplicity triggers, allows probing for potential jet quenching effects in high-multiplicity events (with up to 400 charged particles), for which collective phenomena consistent with quark-gluon plasma (QGP) droplet formation were previously observed. The ratios of xj x_{j} distributions for high- to low-multiplicity events are used to quantify the possible medium effects. These ratios are consistent with simulations of the hard-scattering process that do not include QGP production. These measurements set an upper limit on medium-induced energy loss of the subleading jet of 1.26% of its transverse momentum at the 90% confidence level in high multiplicity pPb events.The first measurement of the dijet transverse momentum balance xj_{j} in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of sNN\sqrt{{s}_{\text{NN}}} = 8.16 TeV is presented. The xj_{j} observable, defined as the ratio of the subleading over leading jet transverse momentum in a dijet pair, is used to search for jet quenching effects. The data, corresponding to an integrated luminosity of 174.6 nb1^{−1}, were collected with the CMS detector in 2016. The xj_{j} distributions and their average values are studied as functions of the charged-particle multiplicity of the events and for various dijet rapidity selections. The latter enables probing hard scattering of partons carrying distinct nucleon momentum fractions x in the proton- and lead-going directions. The former, aided by the high-multiplicity triggers, allows probing for potential jet quenching effects in high-multiplicity events (with up to 400 charged particles), for which collective phenomena consistent with quark-gluon plasma (QGP) droplet formation were previously observed. The ratios of xj_{j} distributions for high- to low-multiplicity events are used to quantify the possible medium effects. These ratios are consistent with simulations of the hard-scattering process that do not include QGP production. These measurements set an upper limit on medium-induced energy loss of the subleading jet of 1.26% of its transverse momentum at the 90% confidence level in high multiplicity pPb events.[graphic not available: see fulltext]The first measurement of the dijet transverse momentum balance xjx_j in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of sNN\sqrt{s_\mathrm{NN}} = 8.16 TeV is presented. The xjx_j observable, defined as the ratio of the subleading over leading jet transverse momentum in a dijet pair, is used to search for jet quenching effects. The data, corresponding to an integrated luminosity of 174.6 nb1^{-1}, were collected with the CMS detector in 2016. The xjx_j distributions and their average values are studied as functions of the charged-particle multiplicity of the events and for various dijet rapidity selections. The latter enables probing hard scattering of partons carrying distinct nucleon momentum fractions xx in the proton- and lead-going directions. The former, aided by the high-multiplicity triggers, allows probing for potential jet quenching effects in high-multiplicity events (with up to 400 charged particles), for which collective phenomena consistent with quark-gluon plasma (QGP) droplet formation were previously observed. The ratios of xjx_j distributions for high- to low-multiplicity events are used to quantify the possible medium effects. These ratios are consistent with simulations of the hard-scattering process that do not include QGP production. These measurements set an upper limit on medium-induced energy loss of the subleading jet of 1.26% of its transverse momentum at the 90% confidence level in high multiplicity pPb events

    Measurements of Higgs boson production cross section in the four-lepton final state in proton-proton collisions at s= \sqrt{s} = 13.6 TeV

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    The measurements of the Higgs boson (H) production cross sections performed by the CMS Collaboration in the four-lepton (4 ,=e,μ \ell, \ell=\mathrm{e},\mu ) final state at a center-of-mass energy s= \sqrt{s}= 13.6 TeV are presented. These measurements are based on data collected with the CMS detector at the CERN LHC in 2022, corresponding to an integrated luminosity of 34.7 fb1 ^{-1} . Cross sections are measured in a fiducial region closely matching the experimental acceptance, both inclusively and differentially, as a function of the transverse momentum and the absolute value of the rapidity of the four-lepton system. The HZZ4 \mathrm{H}\to\mathrm{Z}\mathrm{Z}\to 4\ell inclusive fiducial cross section is measured to be 2.89 0.49+0.53 ^{+0.53}_{-0.49} (stat) 0.21+0.29^{+0.29}_{-0.21} (syst) fb, in agreement with the standard model expectation of 3.09 0.24+0.27 ^{+0.27}_{-0.24} fb.The measurements of the Higgs boson (H) production cross sections performed by the CMS Collaboration in the four-lepton (4ℓ, ℓ = e, μ) final state at a center-of-mass energy s\sqrt{s} = 13.6 TeV are presented. These measurements are based on data collected with the CMS detector at the CERN LHC in 2022, corresponding to an integrated luminosity of 34.7 fb1^{−1}. Cross sections are measured in a fiducial region closely matching the experimental acceptance, both inclusively and differentially, as a function of the transverse momentum and the absolute value of the rapidity of the four-lepton system. The H → ZZ → 4ℓ inclusive fiducial cross section is measured to be 2.890.49+0.53(stat)0.21+0.29(syst){2.89}_{-0.49}^{+0.53}{\left({\text{stat}}\right)}_{-0.21}^{+0.29}\left({\text{syst}}\right) fb, in agreement with the standard model expectation of 3.090.24+0.27{3.09}_{-0.24}^{+0.27} fb.[graphic not available: see fulltext]The measurements of the Higgs boson (H) production cross sections performed by the CMS Collaboration in the four-lepton (4\ell, \ell = e, μ\mu) final state at a center-of-mass energy s\sqrt{s} = 13.6 TeV are presented. These measurements are based on data collected with the CMS detector at the CERN LHC in 2022, corresponding to an integrated luminosity of 34.7 fb1^{-1}. Cross sections are measured in a fiducial region closely matching the experimental acceptance, both inclusively and differentially, as a function of the transverse momentum and the absolute value of the rapidity of the four-lepton system. The H \to ZZ \to 4\ell inclusive fiducial cross section is measured to be 2.89 0.49+0.53^{+0.53}_{-0.49} (stat) 0.21+0.29^{+0.29}_{-0.21} (syst) fb, in agreement with the standard model expectation of 3.09 0.24+0.27^{+0.27}_{-0.24} fb

    Operation and performance of the CMS silicon strip tracker with proton-proton collisions at the CERN LHC

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    International audienceSalient aspects of the commissioning, calibration, and performance of the CMS silicon strip tracker are discussed, drawing on experience during operation with proton-proton collisions delivered by the CERN LHC. The data were obtained with a variety of luminosities. The operating temperature of the strip tracker was changed several times during this period and results are shown as a function of temperature in several cases. Details of the system performance are presented, including occupancy, signal-to-noise ratio, Lorentz angle, and single-hit spatial resolution. Saturation effects in the APV25 readout chip preamplifier observed during early Run 2 are presented, showing the effect on various observables and the subsequent remedy. Studies of radiation effects on the strip tracker are presented both for the optical readout links and the silicon sensors. The observed effects are compared to simulation, where available, and they generally agree well with expectations

    Measurement of the dineutrino system kinematic variables in dileptonic top quark pair production in proton-proton collisions ats\sqrt{s} = 13 TeV

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    International audienceDifferential top quark pair production cross sections are measured in the dilepton final states e+^+e^-, μ+μμ^+μ^-, and e±μ^\pmμ^\mp, as a function of kinematic variables of the two-neutrino system: the transverse momentum pTννp_\mathrm{T}^{νν} of the dineutrino system, the minimum distance in azimuthal angle between pTνν\vec{p}_\mathrm{T}^{\,νν} and leptons, and in two dimensions in bins of both observables. The measurements are performed using CERN LHC proton-proton collisions at s\sqrt{s} = 13 TeV, recorded by the CMS detector between 2016 and 2018, corresponding to an integrated luminosity of 138 fb1^{-1}. The measured cross sections are unfolded to the particle level using an unregularized least squares method. Results are compared with predictions by the standard model of particle physics, and found to be in agreement with theoretical calculations as well as Monte Carlo simulations

    Search for heavy pseudoscalar and scalar bosons decaying to a top quark pair in proton-proton collisions at s= \sqrt{s}= 13 TeV

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    A search for pseudoscalar or scalar bosons decaying to a top quark pair (tt \mathrm{t} \overline{\mathrm{t}} ) in final states with one or two charged leptons is presented. The analyzed proton-proton collision data was recorded at s= \sqrt{s}= 13 TeV by the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 138 fb1 ^{-1} . The invariant mass mtt m_{{\mathrm{t}\overline{\mathrm{t}}} } of the reconstructed tt \mathrm{t} \overline{\mathrm{t}} system and variables sensitive to its spin and parity are used to discriminate against the standard model tt \mathrm{t} \overline{\mathrm{t}} background. Interference between pseudoscalar or scalar boson production and the standard model tt \mathrm{t} \overline{\mathrm{t}} continuum is included, leading to peak-dip structures in the mtt m_{{\mathrm{t}\overline{\mathrm{t}}} } distribution. An excess of the data above the background prediction, based on perturbative quantum chromodynamics (QCD) calculations, is observed near the kinematic tt \mathrm{t} \overline{\mathrm{t}} production threshold, while good agreement is found for high mtt m_{{\mathrm{t}\overline{\mathrm{t}}} } . The data are consistent with the background prediction if the contribution from the production of a color-singlet 1S0[1] ^1\mathrm{S}_0^{[1]} tt \mathrm{t} \overline{\mathrm{t}} quasi-bound state ηt \eta_{\mathrm{t}}, predicted by nonrelativistic QCD, is added. Upper limits at 95% confidence level are set on the coupling between the pseudoscalar or scalar bosons and the top quark for boson masses in the range 365-1000 GeV, relative widths between 0.5 and 25%, and two background scenarios with or without ηt \eta_{\mathrm{t}} contribution.A search for pseudoscalar or scalar bosons decaying to a top quark pair (ttˉ\mathrm{t\bar{t}}) in final states with one or two charged leptons is presented. The analyzed proton-proton collision data was recorded at s\sqrt{s} = 13 TeV by the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 138 fb1^{-1}. The invariant mass mttˉm_\mathrm{t\bar{t}} of the reconstructed ttˉ\mathrm{t\bar{t}} system and variables sensitive to its spin and parity are used to discriminate against the standard model ttˉ\mathrm{t\bar{t}} background. Interference between pseudoscalar or scalar boson production and the standard model ttˉ\mathrm{t\bar{t}} continuum is included, leading to peak-dip structures in the mttˉm_\mathrm{t\bar{t}} distribution. An excess of the data above the background prediction, based on perturbative quantum chromodynamics (QCD) calculations, is observed near the kinematic ttˉ\mathrm{t\bar{t}} production threshold, while good agreement is found for high mttˉm_\mathrm{t\bar{t}}. The data are consistent with the background prediction if the contribution from the production of a color-singlet 1S0[1]{}^1\mathrm{S}_0^{[1]}ttˉ\mathrm{t\bar{t}} quasi-bound state ηtη_\mathrm{t}, predicted by nonrelativistic QCD, is added. Upper limits at 95% confidence level are set on the coupling between the pseudoscalar or scalar bosons and the top quark for boson masses in the range 365-1000 GeV, relative widths between 0.5 and 25%, and two background scenarios with or without ηtη_\mathrm{t} contribution
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