515664 research outputs found
Sort by
Measurements of production cross-sections in collisions at TeV with the ATLAS detector
No full textMeasurements of production cross-sections are presented, providing a test of the predictions of perturbative quantum chromodynamics and the electroweak theory. The measurements are based on data from collisions at TeV recorded by the ATLAS detector at the Large Hadron Collider in 2015-2018, corresponding to an integrated luminosity of 140 fb. The number of events due to top-quark pair production, the largest background, is reduced by rejecting events containing jets with -hadron decays. An improved methodology for estimating the remaining top-quark background enables a precise measurement of cross-sections with no additional requirements on jets. The fiducial cross-section is determined in a maximum-likelihood fit with an uncertainty of 3.1%. The measurement is extrapolated to the full phase space, resulting in a total cross-section of pb. Differential cross-sections are measured as a function of twelve observables that comprehensively describe the kinematics of events. The measurements are compared with state-of-the-art theory calculations and excellent agreement with predictions is observed. A charge asymmetry in the lepton rapidity is observed as a function of the dilepton invariant mass, in agreement with the Standard Model expectation. A CP-odd observable is measured to be consistent with no CP violation. Limits on Standard Model effective field theory Wilson coefficients in the Warsaw basis are obtained from the differential cross-sections.Measurements of WW → eνμν production cross-sections are presented, providing a test of the predictions of perturbative quantum chromodynamics and the electroweak theory. The measurements are based on data from pp collisions at = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider in 2015–2018, corresponding to an integrated luminosity of 140 fb. The number of events due to top-quark pair production, the largest background, is reduced by rejecting events containing jets with b-hadron decays. An improved methodology for estimating the remaining top-quark background enables a precise measurement of WW cross-sections with no additional requirements on jets. The fiducial WW cross-section is determined in a maximum-likelihood fit with an uncertainty of 3.1%. The measurement is extrapolated to the full phase space, resulting in a total WW cross-section of 127 ± 4 pb. Differential cross-sections are measured as a function of twelve observables that comprehensively describe the kinematics of WW events. The measurements are compared with state-of-the-art theory calculations and excellent agreement with predictions is observed. A charge asymmetry in the lepton rapidity is observed as a function of the dilepton invariant mass, in agreement with the Standard Model expectation. A CP-odd observable is measured to be consistent with no CP violation. Limits on Standard Model effective field theory Wilson coefficients in the Warsaw basis are obtained from the differential cross-sections.[graphic not available: see fulltext]Measurements of production cross-sections are presented, providing a test of the predictions of perturbative quantum chromodynamics and the electroweak theory. The measurements are based on data from collisions at TeV recorded by the ATLAS detector at the Large Hadron Collider in 2015-2018, corresponding to an integrated luminosity of 140 fb. The number of events due to top-quark pair production, the largest background, is reduced by rejecting events containing jets with -hadron decays. An improved methodology for estimating the remaining top-quark background enables a precise measurement of cross-sections with no additional requirements on jets. The fiducial cross-section is determined in a maximum-likelihood fit with an uncertainty of 3.1%. The measurement is extrapolated to the full phase space, resulting in a total cross-section of pb. Differential cross-sections are measured as a function of twelve observables that comprehensively describe the kinematics of events. The measurements are compared with state-of-the-art theory calculations and excellent agreement with predictions is observed. A charge asymmetry in the lepton rapidity is observed as a function of the dilepton invariant mass, in agreement with the Standard Model expectation. A CP-odd observable is measured to be consistent with no CP violation. Limits on Standard Model effective field theory Wilson coefficients in the Warsaw basis are obtained from the differential cross-sections
Evidence for Longitudinally Polarized Bosons in the Electroweak Production of Same-Sign Boson Pairs in Association With Two Jets With the ATLAS Detector
No full textThese proceedings describe the first evidence for the longitudinal polarization in electroweak same-charged boson scattering and the most stringent limit on the fully longitudinally polarized scattering. The analysis is based on the Run 2 data of the ATLAS experiment at the LHC with proton collisions at a center-of-mass energy of , corresponding to an integrated luminosity of . The studied final state consists of two same-charged leptons (electrons or muons), missing transverse momentum, and at least two well-separated jets with a high invariant mass. The sensitivity to the polarization states is obtained using deep neural networks. The longitudinal polarization is measured in two independent maximum likelihood fits. The first fit targets the electroweak scattering with at least one boson being longitudinally polarized, leading to an observed significance of . The second fit sets a limit on the fully longitudinally polarized scattering, yielding an observed upper limit of at confidence level
Search for light pseudoscalar a bosons in decays in pp collisions at = 13 TeV
No full text% A search for pairs of neutral resonances resulting from the decay of a Higgs boson is performed, using proton-proton collision data at , corresponding to an integrated luminosity of . The search is conducted for sub-GeV mass resonances which decay into electron-positron pairs. Due to the low mass of these resonances, their decay products are highly collimated and are reconstructed as an electron-positron pair merged into a single object. A novel multivariate identification technique is developed to identify these distinctive signatures, and events are selected with two such merged electron-positron pairs. No significant excess above the standard model prediction is observed. Upper limits on the branching fraction of the Higgs boson decay to two sub-GeV neutral resonances, each decaying to an electron-positron pair, are set at the confidence level, reaching sensitivities as low as . The measured limits are further interpreted in an effective axion-like particle and Higgs-coupling model, confirming the LHC's potential as a unique axion-like particle search facility.
A search for pairs of light neutral bosons (a) resulting from the decay of a Higgs boson
is performed. The a bosons have a mass in the range of 10 to 100 MeV and decay into an electron-positron pair.
The search is conducted using proton-proton collision data at , corresponding to
an integrated luminosity of . Due to the low mass of the a bosons
their decay products are highly collimated and are merged into single detector objects.
A novel multivariate identification technique is developed to identify these distinctive signatures,
and events are selected with two such merged electron-positron pairs.
No significant excess above the standard model prediction is observed.
Upper limits on the branching fraction for are set at the confidence level,
reaching sensitivities as low as . The measured limits are further interpreted in an effective axion-like particle and Higgs-coupling model, confirming the LHC's potential as a unique
axion-like particle search facility
Search for CP violation in production in 13 TeV collisions with the ATLAS detector
No full textThis note presents a search for CP violation in the production of a Higgs boson in association with a boson () using proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider during Run 2, corresponding to an integrated luminosity of at a center-of-mass energy of 13 TeV. The analysis focuses on the decay channels of the Higgs boson to pairs of bottom quarks and the boson to leptons. Fiducial cross-section measurements are performed in the simplified template cross section formalism in bins of an angular variable and the boson transverse momentum, providing a sensitive probe to CP-violating components in the vertex. The results are interpreted within the framework of the Standard Model Effective Field Theory (SMEFT), and constraints are set on the relevant Wilson coefficient in the Warsaw basis, , with an observed (expected) value of [-0.62, 0.85]~([-0.58, 0.59]) at 95% confidence level, computed at a new physics scale ~TeV
Search for supersymmetry in hadronic and leptonic final states with highly Lorentz-boosted objects at sqrt(s) = 13 TeV
No full textA search for supersymmetry in final states with highly Lorentz-boosted top quarks, , , Higgs bosons, or leptonic jets is presented. The search is based on proton-proton collision data at a center-of-mass energy of , collected by the CMS experiment at CERN LHC during 2016, 2017, and 2018, corresponding to an integrated luminosity of . Candidates for boosted top quark and , , or Higgs boson decays are identified using jet substructure techniques. In addition, leptonic decays of boosted standard model or supersymmetry particles are explored by identifying boosted leptonic jets. The analysis is performed in channels with zero leptons, an isolated lepton, or a nonisolated lepton. Signal events are discriminated from standard model background events using the razor kinematic variables, which characterize signals with massive particles decaying to visible particles and massive invisible particles as a peak above the smoothly falling background. Standard model backgrounds are estimated by deriving data over simulation correction factors in background-enriched control regions. Data are consistent with standard model expectations. The results are interpreted using several simplified supersymmetry models with pair production of gluinos, top squarks, bottom squarks, and electroweakinos, featuring both -parity-conserving and -parity-violating decay chains
First measurement of -jet mass with and without grooming
No full textThe LHCb collaboration presents a novel suite of heavy-flavour jet substructure measurements at forward rapidity in proton-proton collisions at a centre-of-mass energy of TeV. The jet mass is a perturbatively calculable probe of the virtuality of hard-scattered quarks and gluons, connecting small-distance quantum chromodynamics (QCD) with long-distance experimental measurement. It becomes dominated by nonperturbative corrections at small values, presenting an excellent test of QCD across a broad range of energies. Measuring heavy-flavour jet mass with a theoretically unambiguous flavour definition for the first time probes the gluon splitting mechanism for heavy-flavour production and pushes tests of perturbative QCD to unprecedented theoretical precision. Utilising the soft drop jet-grooming technique to access the perturbative jet core further enhances constraints on first-principles theory. Measurements of the jet mass for jets containing fully reconstructed hadrons are reported with and without grooming. These results offer unparalleled tests of quark flavour and mass dependence in QCD and provide a baseline for future studies of heavy-flavour jet quenching in heavy-ion collisions.The LHCb collaboration presents a novel suite of heavy-flavour jet substructure measurements at forward rapidity in proton-proton collisions at a centre-of-mass energy of s=13TeV. The jet mass is a perturbatively calculable probe of the virtuality of hard-scattered quarks and gluons, connecting small-distance quantum chromodynamics (QCD) with long-distance experimental measurement. The jet mass is dominated by nonperturbative corrections at small values, presenting an excellent test of QCD across a broad range of jet energies. Measuring heavy-flavour jet mass with a theoretically unambiguous flavour definition for the first time probes the gluon splitting mechanism for heavy-flavour production and offers tests of perturbative QCD at new levels of theoretical precision. Utilising the soft drop jet-grooming technique to access the perturbative jet core further enhances constraints on first-principles theory. Measurements of the jet mass for jets containing fully reconstructed B± hadrons are reported with and without grooming. The unique phase space instrumented by LHCb offers a different quark-gluon fraction than at midrapidity. These results offer unparalleled tests of quark flavour and mass dependence in QCD and provide a baseline for future studies of heavy-flavour jet quenching in heavy-ion collisions.The LHCb collaboration presents a novel suite of heavy-flavour jet substructure measurements at forward rapidity in proton-proton collisions at a centre-of-mass energy of TeV. The jet mass is a perturbatively calculable probe of the virtuality of hard-scattered quarks and gluons, connecting small-distance quantum chromodynamics (QCD) with long-distance experimental measurement. It becomes dominated by nonperturbative corrections at small values, presenting an excellent test of QCD across a broad range of energies. Measuring heavy-flavour jet mass with a theoretically unambiguous flavour definition for the first time probes the gluon splitting mechanism for heavy-flavour production and pushes tests of perturbative QCD to unprecedented theoretical precision. Utilising the soft drop jet-grooming technique to access the perturbative jet core further enhances constraints on first-principles theory. Measurements of the jet mass for jets containing fully reconstructed hadrons are reported with and without grooming. These results offer unparalleled tests of quark flavour and mass dependence in QCD and provide a baseline for future studies of heavy-flavour jet quenching in heavy-ion collisions
Open Hardware at CERN in practice: electronics
No full textThis presentation introduces the [Open Hardware Repository][1] (OHWR) - a curated, easy-to-browse catalogue of open-source hardware designs. We'll explore together its history and key features, with a focus on how hardware designers can leverage OHWR to showcase their work, foster design reuse, get feedback and contribute to a growing community of open-source hardware for physics experiments across the world.
[1]: https://ohwr.org
CMS Newsletter May 2025 - Point Cinq
No full textThe May 2025 Point Cinq - the monthly CMS newsletter
FCC conceptual waste heat distribution system
No full textThe Future Circular Collider (FCC) is a proposed next-generation particle accelerator intended to extend the energy frontier of physics research. As part of its large-scale infrastructure, the FCC will generate significant amounts of low-grade waste heat through its cooling systems, heat that can potentially be recovered and reused locally. The image illustrates a conceptual waste heat distribution system at FCC’s PD-site, showing how thermal energy from the collider’s cooling circuits could be supplied to nearby users, primarily the Fromagerie de la Tournette
Simulation of charge transport at the surface of planar silicon sensors
No full textRadiation-hard silicon sensors used in high-energy physics require a high electric field and are susceptible to surface breakdown. This study aims to improve the understanding of the underlying mechanisms by developing new methods to probe the electric field at surface near the sensor’s edge. For planar sensors, avalanche breakdown primarily occurs at the Si-SiO-interface, where localized electric field peaks can form between the guard ring and the edge. Accurate simulations are challenging and it is essential to validate simulation parameters by comparing the simulation results to measurements. In this work, the electrical behavior of the edge region of planar silicon diodes was simulated using Synopsis TCAD. Transient Current Technique (TCT) simulations were performed in both TCAD and Allpix, and compared to measurements. Additionally, laser scans over the edge region were performed in Allpix to evaluate the simulated surface electric field and charge collection efficiency