8 research outputs found
Measurements of and production in collisions at TeV with the ATLAS detector
No full textSee paper for full list of authors - 42 pages in total, author list starting page 26, 10 figures, 8 tables. Submitted to JHEP. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/BPHY-2015-03/International audienceDifferential cross sections are presented for the prompt and non-prompt production of the hidden-charm states and , in the decay mode , measured using 11.4 fb of collisions at TeV by the ATLAS detector at the LHC. The ratio of cross-sections is also given, separately for prompt and non-prompt components, as well as the non-prompt fractions of and . Assuming independent single effective lifetimes for non-prompt and production gives , while separating short- and long-lived contributions, assuming that the short-lived component is due to decays, gives , with the fraction of non-prompt produced via decays for GeV being . The distributions of the dipion invariant mass in the and decays are also measured and compared to theoretical predictions
Search for direct top squark pair production in final states with two leptons in root s=13 TeV pp collisions with the ATLAS detector
No full textThe results of a search for direct pair production of top squarks in events with two opposite-charge leptons (electrons or muons) are reported, using of integrated luminosity from proton–proton collisions at TeV collected by the ATLAS detector at the Large Hadron Collider. To cover a range of mass differences between the top squark and lighter supersymmetric particles, four possible decay modes of the top squark are targeted with dedicated selections: the decay into a b-quark and the lightest chargino with , the decay into an on-shell top quark and the lightest neutralino, the three-body decay and the four-body decay . No significant excess of events is observed above the Standard Model background for any selection, and limits on top squarks are set as a function of the and masses. The results exclude at 95% confidence level masses up to about 720 GeV, extending the exclusion region of supersymmetric parameter space covered by previous searches
Improved determination of the sample composition of dimuon events produced in p(p)over-bar collisions at root s=1.96 TeV
No full textWe use a new method to estimate with 5% accuracy the contribution of pion and kaon in-flight-decays to the dimuon data set acquired with the CDF detector. Based on this improved estimate, we show that the total number and the properties of the collected dimuon events are not yet accounted for by ordinary sources of dimuons which also include the contributions, as measured in the data, of heavy flavor, Υ{hooked}, and Drell-Yan production in addition to muons mimicked by hadronic punchthrough. The number of unaccounted events corresponds to (12.8±3.2)% of the bb̄ production. We find that (23±6)% of the unaccounted events contain additional muon candidates. For comparison, this fraction is (6.9±0.4)% for events due to bb̄ production. © 2011 The Author(s)
Search for scalar leptoquarks in pp collisions at s√=13 TeV with the ATLAS experiment
No full textSee paper for full list authors -25 pages + author list (45 pages in total) , 7 figures and 4 tables, submitted to New Journal of Physics, all figures including auxiliary figures are available at this https URLInternational audienceAn inclusive search for a new-physics signature of lepton-jet resonances has been performed by the ATLAS experiment. Scalar leptoquarks, pair-produced in pp collisions at s√ = 13 TeV at the Large Hadron Collider have been considered. An integrated luminosity of 3.2 fb−1, corresponding to the full 2015 dataset was used. First (second) generation leptoquarks were sought in events with two electrons (muons) and two or more jets. The observed yield in each channel is consistent with Standard Model background expectations. The observed (expected) leptoquark mass limits at 95% confidence level are 1100 GeV and 1050 GeV (1160 GeV and 1040 GeV) for first and second generation leptoquarks, respectively, assuming a branching ratio into a charged lepton and a quark of 100%. Upper limits on the aforementioned branching ratio are also given as a function of leptoquark mass. Compared with the results of earlier ATLAS searches, the sensitivity is increased for the higher range of accessible leptoquark masses, and the observed exclusion limits confirm and extend the published results
Search for direct top squark pair production in final states with two leptons in root s=13 TeV pp collisions with the ATLAS detector
No full textThe results of a search for direct pair production of top squarks in events with two opposite-charge leptons (electrons or muons) are reported, using 36.1 fb - 1 of integrated luminosity from proton-proton collisions at s = 13 TeV collected by the ATLAS detector at the Large Hadron Collider. To cover a range of mass differences between the top squark t ~ and lighter supersymmetric particles, four possible decay modes of the top squark are targeted with dedicated selections: the decay t ~ → b χ ~ 1 ± into a b-quark and the lightest chargino with χ ~ 1 ± → W χ ~ 1 0 , the decay t ~ → t χ ~ 1 0 into an on-shell top quark and the lightest neutralino, the three-body decay t ~ → b W χ ~ 1 0 and the four-body decay t ~ → b ℓ ν χ ~ 1 0 . No significant excess of events is observed above the Standard Model background for any selection, and limits on top squarks are set as a function of the t ~ and χ ~ 1 0 masses. The results exclude at 95% confidence level t ~ masses up to about 720 GeV, extending the exclusion region of supersymmetric parameter space covered by previous searches
Search for new phenomena using the invariant mass distribution of same-flavour opposite-sign dilepton pairs in events with missing transverse momentum in s=13 Te<i>pp</i> collisions with the ATLAS detector.
No full textSearch for direct top squark pair production in final states with two leptons in s=13 TeV pp collisions with the ATLAS detector
No full textSearch for new phenomena using the invariant mass distribution of same-flavour opposite-sign dilepton pairs in events with missing transverse momentum in √s=13 Te pp collisions with the ATLAS detector
No full textA search for new phenomena in final states containing an e+e-or μ+μ-pair, jets, and large missing transverse momentum is presented. This analysis makes use of proton–proton collision data with an integrated luminosity of 36.1fb-1, collected during 2015 and 2016 at a centre-of-mass energy s=13TeV with the ATLAS detector at the Large Hadron Collider. The search targets the pair production of supersymmetric coloured particles (squarks or gluinos) and their decays into final states containing an e+e-or μ+μ-pair and the lightest neutralino (χ~10) via one of two next-to-lightest neutralino (χ~20) decay mechanisms: χ~20→Zχ~10, where the Z boson decays leptonically leading to a peak in the dilepton invariant mass distribution around the Z boson mass; and χ~20→l+l-χ~10 with no intermediate l+l-resonance, yielding a kinematic endpoint in the dilepton invariant mass spectrum. The data are found to be consistent with the Standard Model expectation. Results are interpreted using simplified models, and exclude gluinos and squarks with masses as large as 1.85 and 1.3 Te at 95% confidence level, respectively
