13 research outputs found

    Future Circular Collider Feasibility Study Report Volume 2: Accelerators, technical infrastructure and safety

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    In response to the 2020 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) Feasibility Study was launched as an international collaboration hosted by CERN. The FCC ‘integrated programme’, described in this report, in a first stage consists of a highest-luminosity electron-positron collider, FCC-ee, serving as Higgs, top and electroweak factory, with a subsequent energy-frontier proton-proton collider, FCC-hh, as the second stage.     The FCC-ee is designed to operate at four baseline centre-of-mass energies, corresponding to the Z pole, the WW pair production threshold, the ZH production peak, and the top/anti-top production threshold, always delivering the highest possible luminosities to four experiments. Over a span of 15 years, FCC-ee will produce more than 6 trillion Z bosons, 200 million WW pairs, almost 3 million Higgs bosons,  and 2 million top anti-top pairs. On the Z pole and at the WW pair threshold, the collision energy can be precisely calibrated by frequent resonant depolarisation of pilot bunches. The sequence of operation modes and beam energies is flexible, between the Z, WW and ZH substages. The hadron collider, FCC-hh, will operate at a centre-of-mass energy of about 85 TeV, extending the energy frontier by almost an order of magnitude compared with the LHC, and providing integrated luminosity 5-10 times higher than that of the upcoming High-Luminosity LHC. The mass reach for direct discovery at the FCC-hh amounts to several tens of TeV. The FCC-hh can also accommodate ion-ion, ion-hadron, and lepton-hadron collision options.   This second volume of the Feasibility Study Report covers the complete design of the FCC-ee collider, the operation and staging concepts, the design of the full-energy booster and of the FCC-ee injector complex, the accelerator technologies required, safety concepts, and technical infrastructures,  along with the design of the FCC-hh hadron collider, the associated high-field magnet developments, hadron injector options, and FCC-hh key technical systems.In response to the 2020 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) Feasibility Study was launched as an international collaboration hosted by CERN. This report describes the FCC integrated programme, which consists of two stages: an electron-positron collider (FCC-ee) in the first phase, serving as a high-luminosity Higgs, top, and electroweak factory; followed by a proton-proton collider (FCC-hh) at the energy frontier in the second phase. FCC-ee is designed to operate at four key centre-of-mass energies: the Z pole, the WW production threshold, the ZH production peak, and the top/anti-top production threshold - delivering the highest possible luminosities to four experiments. Over 15 years of operation, FCC-ee will produce more than 6 trillion Z bosons, 200 million WW pairs, nearly 3 million Higgs bosons, and 2 million top anti-top pairs. Precise energy calibration at the Z pole and WW threshold will be achieved through frequent resonant depolarisation of pilot bunches. The sequence of operation modes remains flexible. FCC-hh will operate at a centre-of-mass energy of approximately 85 TeV - nearly an order of magnitude higher than the LHC - and is designed to deliver 5 to 10 times the integrated luminosity of the HL-LHC. Its mass reach for direct discovery extends to several tens of TeV. In addition to proton-proton collisions, FCC-hh is capable of supporting ion-ion, ion-proton, and lepton-hadron collision modes. This second volume of the Feasibility Study Report presents the complete design of the FCC-ee collider, its operation and staging strategy, the full-energy booster and injector complex, required accelerator technologies, safety concepts, and technical infrastructure. It also includes the design of the FCC-hh hadron collider, development of high-field magnets, hadron injector options, and key technical systems for FCC-hh

    Futur collisionneur circulaire—Rapport d’étude de faisabilité, volume 3: Génie civil, implantation et durabilité

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    Measurement of inclusive and differential cross sections of single top quark production in association with a W boson in proton-proton collisions at s = 13.6 TeV

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    The first measurement of the inclusive and normalised differential cross sections of single top quark production in association with a W boson in proton-proton collisions at a centre-of-mass energy of 13.6 TeV is presented. The data were recorded with the CMS detector at the LHC in 2022, and correspond to an integrated luminosity of 34.7 fb−1. The analysed events contain one muon and one electron in the final state. For the inclusive measurement, multivariate discriminants exploiting the kinematic properties of the events are used to separate the signal from the dominant top quark-antiquark production background. A cross section of 82.3±2.1stat−9.7+9.9syst±3.3lumi pb is obtained, consistent with the predictions of the standard model. A fiducial region is defined according to the detector acceptance to perform the differential measurements. The resulting differential distributions are unfolded to particle level and show good agreement with the predictions at next-to-leading order in perturbative quantum chromodynamics

    Identification of low-momentum muons in the CMS detector using multivariate techniques in proton-proton collisions at √s = 13.6 TeV

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    "Soft"muons with a transverse momentum below 10 GeV are featured in many processes studied by the CMS experiment, such as decays of heavy-flavor hadrons or rare tau lepton decays. Maximizing the selection efficiency for these muons, while simultaneously suppressing backgrounds from long-lived light-flavor hadron decays, is therefore important for the success of the CMS physics program. Multivariate techniques have been shown to deliver better muon identification performance than traditional selection techniques. To take full advantage of the large data set currently being collected during Run 3 of the CERN LHC, a new multivariate classifier based on a gradient-boosted decision tree has been developed. It offers a significantly improved separation of signal and background muons compared to a similar classifier used for the analysis of the Run 2 data. The performance of the new classifier is evaluated on a data set collected with the CMS detector in 2022 and 2023, corresponding to an integrated luminosity of 62 fb-

    Search for rare decays of the Z and Higgs bosons to a J/ψ or ψ(2S) meson and a photon in proton-proton collisions at s=13TeV

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    A search is presented for rare decays of the Image 1 and Higgs bosons to a photon and a Image 2 or a Image 3 meson, with the charmonium state subsequentially decaying to a pair of muons. The data set corresponds to an integrated luminosity of 123fb−1 of proton-proton collisions at a center-of-mass energy of 13 TeV collected with the CMS detector at the LHC. No evidence for branching fractions of these rare decay channels larger than predicted in the standard model is observed. Upper limits at 95% confidence level are set: Image 4, Image 5, Image 6, and Image 7. The ratio of the Higgs boson coupling modifiers Image 8 is constrained to be in the interval (−157,+199) at 95% confidence level. Assuming Image 9, this interval becomes (−166,+208)

    Search for the Higgs boson decays to a ρ0, ϕ, or K⁎0 meson and a photon in proton-proton collisions at s=13TeV

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    Three rare decay processes of the Higgs boson to a ρ(770)0, ϕ(1020), or K⁎(892)0 meson and a photon are searched for using s=13TeV proton-proton collision data collected by the CMS experiment at the LHC. Events are selected assuming the mesons decay into a pair of charged pions, a pair of charged kaons, or a charged kaon and pion, respectively. Depending on the Higgs boson production mode, different triggering and reconstruction techniques are adopted. The analyzed data sets correspond to integrated luminosities up to 138fb−1, depending on the reconstructed final state. After combining various data sets and categories, no significant excess above the background expectations is observed. Upper limits at 95% confidence level on the Higgs boson branching fractions into ρ(770)0γ, ϕ(1020)γ, and K⁎(892)0γ are determined to be 3.7×10−4, 3.0×10−4, and 3.0×10−4, respectively. In case of the ρ(770)0γ and ϕ(1020)γ channels, these are the most stringent experimental limits to date

    Observation of nuclear modification of energy-energy correlators inside jets in heavy ion collisions

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    Energy-energy correlators are constructed by averaging the number of charged particle pairs within jets, weighted by the product of their transverse momenta, as a function of the angular separation of the particles within a pair. They are sensitive to a multitude of perturbative and nonperturbative quantum chromodynamics phenomena in high-energy particle collisions. Using lead-lead data recorded with the CMS detector, energy-energy correlators inside high transverse momentum jets are measured in heavy ion collisions for the first time. The data are obtained at a nucleon-nucleon center-of-mass energy of 5.02 TeV and correspond to an integrated luminosity of 1.70nb−1. A similar analysis is done for proton-proton collisions at the same center-of-mass energy to establish a reference. The ratio of lead-lead to proton-proton energy-energy correlators reveals significant jet substructure modifications in the quark-gluon plasma. The results are compared to different models that incorporate either color coherence or medium response effects, where the two effects predict similar substructure modifications

    Search for heavy neutral Higgs bosons A and H in the tt¯Z channel in proton-proton collisions at 13 TeV

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    A direct search for new heavy neutral Higgs bosons Image 1 and Image 2 in the Image 3 channel is presented, targeting the process Image 4 with Image 5. For the first time, the channel with decays of the Image 6 boson to muons or electrons in association with all-hadronic decays of the Image 7 system is targeted. The analysis uses proton-proton collision data collected at the CERN LHC with the CMS experiment at s=13TeV, which correspond to an integrated luminosity of 138fb−1. No signal is observed. Upper limits on the product of the cross section and branching fractions are derived for narrow resonances Image 8 and Image 9 with masses up to 2100 and 2000 GeV, respectively, assuming Image 10 boson production through gluon fusion. The results are also interpreted within two-Higgs-doublet models, where Image 11 and Image 12 are CP-odd and CP-even states, respectively, complementing and substantially extending the reach of previous searches

    Energy-scaling behavior of intrinsic transverse-momentum parameters in Drell-Yan simulation

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    An analysis is presented based on models of the intrinsic transverse momentum (intrinsic (Formula presented)) of partons in nucleons by studying the dilepton transverse momentum in Drell-Yan events. Using parameter tuning in event generators and existing data from fixed-target experiments and from hadron colliders, our investigation spans 3 orders of magnitude in center-of-mass energy and 2 orders of magnitude in dilepton invariant mass. The results show an energy-scaling behavior of the intrinsic (Formula presented) parameters, independent of the dilepton invariant mass at a given center-of-mass energy

    Search for Nuclear Modifications of (Formula presented) Meson Production in (Formula presented)-Pb Collisions at (Formula presented)

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    Nuclear medium effects on (Formula presented) meson production are studied using the binary-collision scaled cross section ratio between events of different charged-particle multiplicities from proton-lead collisions. Data, collected by the CMS experiment in 2016 at a nucleon-nucleon center-of-mass energy of (Formula presented), corresponding to an integrated luminosity of (Formula presented), were used. The scaling factors in the ratio are determined using a novel approach based on the (Formula presented) cross sections measured in the same events. The scaled ratio for (Formula presented) is consistent with unity for all event multiplicities, putting stringent constraints on nuclear modification for heavy flavor. © 2025 CERN, for the CMS Collaboration
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