2,464 research outputs found

    Status of the search for a muon EDM using the frozen-spin technique

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    Despite the many successes of the Standard Model of particle physics, there are still several physical observations that it cannot explain, such as the matter-antimatter asymmetry, non-zero neutrino masses, and the microscopic nature of dark matter. To address these limitations, extensions to the standard model are necessary, and searches for electric dipole moments (EDMs) of leptons are valuable test. The search for a muon EDM is the only search on a bare lepton of the second generation, complementing the searches for an EDM of the electron using polar molecules. A non-zero EDM of the muon would indicate Charge-Parity symmetry violation beyond the standard model. A dedicated experimental search for the muon EDM is being set up at PSI using the frozen-spin technique. In this technique, the anomalous spin precession of the muons in a storage ring is suppressed by applying an electric field in the radial direction. The muon EDM experiment will take place in two phases: the first phase will demonstrate the frozen-spin technique using a precursor experiment with 28 MeV/c muons, while the second phase will make use of 125 MeV/c muons, which could search for the muon EDM with a sensitivity of 6 × 10-23 e·cm. In this talk, we describe the precursor experiment at PSI and provide an update on the status of the experiment

    Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

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    This paper presents measurements of the W+→Ό+ÎœW^+ \rightarrow \mu^+\nu and W−→Ό−ΜW^- \rightarrow \mu^-\nu 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~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 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.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

    Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector