Results of a search for new physics in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an integrated luminosity of 1...
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Results of a search for new physics in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an integrated luminosity of 139 fb−1 at a center-of-mass energy of 13 TeV collected in the period 2015–2018 with the ATLAS detector at the Large Hadron Collider. Compared to previous publications, in addition to an increase of almost a factor of four in the data size, the analysis implements a number of improvements in the signal selection and the background determination leading to enhanced sensitivity. Events are required to have at least one jet with transverse momentum above 150 GeV and no reconstructed leptons (e, μ or τ) or photons. Several signal regions are considered with increasing requirements on the missing transverse momentum starting at 200 GeV. Overall agreement is observed between the number of events in data and the Standard Model predictions. Model-independent 95% confidence-level limits on visible cross sections for new processes are obtained in the range between 736 fb and 0.3 fb. Results are also translated into improved exclusion limits in models with pair-produced weakly interacting dark-matter candidates, large extra spatial dimensions, supersymmetric particles in several compressed scenarios, axionlike particles, and new scalar particles in dark-energy-inspired models. In addition, the data are translated into bounds on the invisible branching ratio of the Higgs boson.
A search for pair production of bottom squarks in events with hadronically decaying τ-leptons, b-tagged jets, and large missing transverse momentum is presented. The analyzed dataset is based on proton-proton collisi...
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A search for pair production of bottom squarks in events with hadronically decaying τ-leptons, b-tagged jets, and large missing transverse momentum is presented. The analyzed dataset is based on proton-proton collisions at s=13 TeV delivered by the Large Hadron Collider and recorded by the ATLAS detector from 2015 to 2018, and corresponds to an integrated luminosity of 139 fb−1. The observed data are compatible with the expected Standard Model background. Results are interpreted in a simplified model where each bottom squark is assumed to decay into the second-lightest neutralino χ˜20 and a bottom quark, with χ˜20 decaying into a Higgs boson and the lightest neutralino χ˜10. The search focuses on final states where at least one Higgs boson decays into a pair of hadronically decaying τ-leptons. This allows the acceptance and thus the sensitivity to be significantly improved relative to the previous results at low masses of the χ˜20, where bottom-squark masses up to 850 GeV are excluded at the 95% confidence level, assuming a mass difference of 130 GeV between χ˜20 and χ˜10. Model-independent upper limits are also set on the cross section of processes beyond the Standard Model.
A search is performed for the electroweak pair production of charginos and associated production of a chargino and neutralino, each of which decays through an R-parity-violating coupling into a lepton and a W, Z, or H...
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A search is performed for the electroweak pair production of charginos and associated production of a chargino and neutralino, each of which decays through an R-parity-violating coupling into a lepton and a W, Z, or Higgs boson. The trilepton invariant-mass spectrum is constructed from events with three or more leptons, targeting chargino decays that include an electron or muon and a leptonically decaying Z boson. The analyzed dataset corresponds to an integrated luminosity of 139 fb−1 of proton-proton collision data produced by the Large Hadron Collider at a center-of-mass energy of s=13 TeV and collected by the ATLAS experiment between 2015 and 2018. The data are found to be consistent with predictions from the Standard Model. The results are interpreted as limits at 95% confidence level on model-independent cross sections for processes beyond the Standard Model. Limits are also set on the production of charginos and neutralinos for a minimal supersymmetric Standard Model with an approximate B−L symmetry. Charginos and neutralinos with masses between 100 and 1100 GeV are excluded depending on the assumed decay branching fractions into a lepton (electron, muon, or τ lepton) plus a boson (W, Z, or Higgs).
Exclusive dimuon production in ultraperipheral collisions (UPC), resulting from photon-photon interactions in the strong electromagnetic fields of colliding high-energy lead nuclei, PbPb(γγ)→μ+μ−(Pb(★)Pb(★)), i...
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Exclusive dimuon production in ultraperipheral collisions (UPC), resulting from photon-photon interactions in the strong electromagnetic fields of colliding high-energy lead nuclei, PbPb(γγ)→μ+μ−(Pb(★)Pb(★)), is studied using Lint=0.48nb−1 of sNN=5.02TeV lead-lead collision data at the LHC with the ATLAS detector. Dimuon pairs are measured in the fiducial region pT,μ>4 GeV, |ημ|<2.4, invariant mass mμμ>10 GeV, and pT,μμ<2 GeV. The primary background from single-dissociative processes is extracted from the data using a template fitting technique. Differential cross sections are presented as a function of mμμ, absolute pair rapidity (|yμμ|), scattering angle in the dimuon rest frame (|cosϑμμ★|), and the colliding photon energies. The total cross section of the UPC γγ→μ+μ− process in the fiducial volume is measured to be σfidμμ=34.1±0.3(stat.)±0.7(syst.) μb. Generally good agreement is found with calculations from STARlight, which incorporate the leading-order Breit-Wheeler process with no final-state effects, albeit differences between the measurements and theoretical expectations are observed. In particular, the measured cross sections at larger |yμμ| are found to be about 10–20% larger in data than in the calculations, suggesting the presence of larger fluxes of photons in the initial state. Modification of the dimuon cross sections in the presence of forward and/or backward neutron production is also studied and is found to be associated with a harder incoming photon spectrum, consistent with expectations.
BACKGROUND:Copy number variants (CNVs) increase risk for neurodevelopmental conditions. The neurobiological mechanisms linking these high-risk genetic variants to clinical phenotypes are largely unknown. An important ...
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BACKGROUND:Copy number variants (CNVs) increase risk for neurodevelopmental conditions. The neurobiological mechanisms linking these high-risk genetic variants to clinical phenotypes are largely unknown. An important question is whether brain abnormalities in individuals carrying CNVs are associated with their degree of penetrance.
METHODS:We investigated if increased CNV-penetrance for schizophrenia and other developmental disorders was associated with variations in cortical and subcortical morphology. We pooled T1-weighted brain magnetic resonance imaging and genetic data from 22 cohorts from the ENIGMA-CNV consortium. In the main analyses, we included 9,268 individuals (aged 7 to 90 years, 54% females), from which we identified 398 carriers of 36 neurodevelopmental CNVs at 20 distinct loci. A secondary analysis was performed including additional neuroimaging data from the ENIGMA-22q consortium, including 274 carriers of the 22q11.2 deletion and 291 non-carriers. CNV-penetrance was estimated through penetrance scores that were previously generated from large cohorts of patients and controls. These scores represent the probability risk to develop either schizophrenia or other developmental disorders (including developmental delay, autism spectrum disorder and congenital malformations).
RESULTS:For both schizophrenia and developmental disorders, increased penetrance scores were associated with lower surface area in the cerebral cortex and lower intracranial volume. For both conditions, associations between CNV-penetrance scores and cortical surface area were strongest in regions of the occipital lobes, specifically in the cuneus and lingual gyrus.
CONCLUSIONS:Our findings link global and regional cortical morphometric features with CNV-penetrance, providing new insights into neurobiological mechanisms of genetic risk for schizophrenia and other developmental disorders.
The mass of the Higgs boson is measured in the H→γγ decay channel, exploiting the high resolution of the invariant mass of photon pairs reconstructed from the decays of Higgs bosons produced in proton–proton colli...
A measurement of the charge asymmetry in top-quark pair (tt¯) production in association with a photon is presented. The measurement is performed in the single-lepton tt¯ decay channel using proton–proton co...
Constraints on the Higgs boson self-coupling are set by combining double-Higgs boson analyses in the bb¯bb¯, bb¯τ+τ− and bb¯γγ decay channels with single-Higgs boson analyses targeting the γγ...
A search for a new pseudoscalar a-boson produced in events with a top-quark pair, where the a-boson decays into a pair of muons, is performed using s=13 TeV pp collision data collected with the ATLAS detector at the ...
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A search for a new pseudoscalar a-boson produced in events with a top-quark pair, where the a-boson decays into a pair of muons, is performed using s=13 TeV pp collision data collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 139 fb−1. The search targets the final state where only one top quark decays to an electron or muon, resulting in a signature with three leptons eμμ and μμμ. No significant excess of events above the Standard Model expectation is observed and upper limits are set on two signal models: pp→tt¯a and pp→tt¯ with t→H±b, H±→W±a, where a→μμ, in the mass ranges 15 GeV
New particles with large masses that decay into hadronically interacting particles are predicted by many models of physics beyond the Standard Model. A search for a massive resonance that decays into pairs of dijet re...
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New particles with large masses that decay into hadronically interacting particles are predicted by many models of physics beyond the Standard Model. A search for a massive resonance that decays into pairs of dijet resonances is performed using 140 fb−1 of proton-proton collisions at s=13 TeV recorded by the ATLAS detector during Run 2 of the Large Hadron Collider. Resonances are searched for in the invariant mass of the tetrajet system, and in the average invariant mass of the pair of dijet systems. A data-driven background estimate is obtained by fitting the tetrajet and dijet invariant mass distributions with a four-parameter dijet function and a search for local excesses from resonant production of dijet pairs is performed. No significant excess of events beyond the Standard Model expectation is observed, and upper limits are set on the production cross sections of new physics scenarios.
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