Search for heavy diboson resonances in semileptonic final states in pp collisions at √s=13 TeV with the ATLAS detector

Indexación ScopusThis paper reports on a search for heavy resonances decaying into WW, ZZ or WZ using proton–proton collision data at a centre-of-mass energy of s=13 TeV. The data, corresponding to an integrated luminosity of 139 fb 1, were recorded with the ATLAS detector from 2015 to 2018 at the Large Hadron Collider. The search is performed for final states in which one W or Z boson decays leptonically, and the other W boson or Z boson decays hadronically. The data are found to be described well by expected backgrounds. Upper bounds on the production cross sections of heavy scalar, vector or tensor resonances are derived in the mass range 300–5000 GeV within the context of Standard Model extensions with warped extra dimensions or including a heavy vector triplet. Production through gluon–gluon fusion, Drell–Yan or vector-boson fusion are considered, depending on the assumed model. © 2020, CERN for the benefit of the ATLAS collaboration.https://link-springer-com.recursosbiblioteca.unab.cl/article/10.1140/epjc/s10052-020-08554-

Measurements of azimuthal anisotropies of jet production in Pb+Pb collisions at root sNN=5.02 TeV with the ATLAS detector

The azimuthal variation of jet yields in heavy-ion collisions provides information about the path-length dependence of the energy loss experienced by partons passing through the hot, dense nuclear matter known as the quark–gluon plasma. This paper presents the azimuthal anisotropy coefficients v2, v3, and v4 measured for jets in Pb + Pb collisions at √ sNN = 5.02 TeV using the ATLAS detector at the LHC. The measurement uses data collected in 2015 and 2018, corresponding to an integrated luminosity of 2.2 nb−1. The vn values are measured as a function of the transverse momentum of the jets between 71 and 398 GeV and the event centrality. A nonzero value of v2 is observed in all but the most central collisions. The value of v2 is largest for jets with lower transverse momentum, with values up to 0.05 in mid-central collisions. A smaller, nonzero value of v3 of approximately 0.01 is measured with no significant dependence on jet pT or centrality, suggesting that fluctuations in the initial state play a small but distinct role in jet energy loss. No significant deviation of v4 from zero is observed in the measured kinematic region.G. Aad … P. Jackson … A.X.Y. Kong … J.L. Oliver … H. Potti … T.A. Ruggeri … A.S. Sharma … M.J. White … et al. [The ATLAS Collaboration

Search for dark matter produced in association with a Standard Model Higgs boson decaying into b-quarks using the full Run 2 dataset from the ATLAS detector

Published: November 26, 2021The production of dark matter in association with Higgs bosons is predicted in several extensions of the Standard Model. An exploration of such scenarios is presented, considering final states with missing transverse momentum and b-tagged jets consistent with a Higgs boson. The analysis uses proton-proton collision data at a centre-of-mass energy of 13 TeV recorded by the ATLAS experiment at the LHC during Run 2, amounting to an integrated luminosity of 139 fb -1 . The analysis, when compared with previous searches, benefits from a larger dataset, but also has further improvements providing sensitivity to a wider spectrum of signal scenarios. These improvements include both an optimised event selection and advances in the object identification, such as the use of the likelihood-based significance of the missing transverse momentum and variable-radius track-jets. No significant deviation from Standard Model expectations is observed. Limits are set, at 95% confidence level, in two benchmark models with two Higgs doublets extended by either a heavy vector boson Z 0 or a pseudoscalar singlet a and which both provide a dark matter candidate chi. In the case of the two-Higgs-doublet model with an additional vector boson Z 0 , the observed limits extend up to a Z 0 mass of 3 TeV for a mass of 100 GeV for the dark matter candidate. The two-Higgs-doublet model with a dark matter particle mass of 10 GeV and an additional pseudoscalar a is excluded for masses of the a up to 520 GeV and 240 GeV for tan beta = 1 and tan beta = 10 respectively. Limits on the visible cross-sections are set and range from to 0.05 fb to 3.26 fb, depending on the missing transverse momentum and b-quark jet multiplicity requirements.The Atlas Collaboration ... G. Aad ... Paul D. Jackson ... Albert X. Kong ... Harish Potti ... Tristan A. Ruggeri ... Martin White ... et al

Search for Lepton-Flavor Violation in Z-Boson Decays with tau Leptons with the ATLAS Detector

Published 28 December 2021A search for lepton-flavor-violating Z → eτ and Z → μτ decays with pp collision data recorded by the ATLAS detector at the LHC is presented. This analysis uses 139 fb−1 of Run 2 pp collisions at ffiffiffi s p ¼ 13 TeV and is combined with the results of a similar ATLAS search in the final state in which the τ lepton decays hadronically, using the same data set as well as Run 1 data. The addition of leptonically decaying τ leptons significantly improves the sensitivity reach for Z → lτ decays. The Z → lτ branching fractions are constrained in this analysis to BðZ → eτÞ < 7.0 × 10−6 and BðZ → μτÞ < 7.2 × 10−6 at 95% confidence level. The combination with the previously published analyses sets the strongest constraints to date: BðZ → eτÞ < 5.0 × 10−6 and BðZ → μτÞ < 6.5 × 10−6 at 95% confidence level.G. Aad ... D. Duvnjak ... P. Jackson ... A. X. Y. Kong ... J. L. Oliver ... H. Potti ... T. A. Ruggeri ... K. Sato ... A. S. Sharma ... M. J. White ... et al. (ATLAS Collaboration

Measurement of the cross-section and charge asymmetry of W bosons produced in proton-proton collisions at root s = 8 TeV with the ATLAS detector

This paper presents measurements of the W⁺→μ⁺ν and W⁻→μ⁻ν cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton–proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2 fb⁻¹. The precision of the cross-section measurements varies between 0.8 and 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.G. Aad ... D. Duvnjak ... P. Jackson ... A. Petridis ... A.S. Sharma ... M.J. White ... et al. [The ATLAS Collaboration