3,467 research outputs found

    The CMS muon system in Run2: preparation, status and first results

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    The CMS muon system has played a key role for many physics results obtained from the LHC Run-1 data. During the Long Shutdown (2013-2014) significant upgrades have been carried out on the muon detectors and on the L1 muon trigger. In parallel the algorithms for muon reconstruction and identification have been improved for both the High-Level Trigger and the offline reconstruction. Results of studies performed on data and Monte Carlo simulations will be presented, with focus on the improvements aiming to ensure an excellent performance in conditions of multiplicity of pileup events and bunch spacing expected during the high-luminosity phase of Run-2. The early muon performance results from LHC Run-2 will be shown.Comment: 8 pages, 13 figures, to be published in the proceedings of EPS-HEP 201

    Status of the MUonE experiment

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    The MUonE experiment has been proposed to measure the differential cross section of ÎĽe\mu e elastic scattering, by colliding the 160 GeV muons of the CERN M2 beam with atomic electrons of thin target plates. From a very precise measurement of the shape one can achieve a competitive determination of the leading hadronic contribution to the muon magnetic moment, independent from the other existing ones. In preparation for the Test Run with a reduced setup the detector geometry has been optimised. Expected yields for a first physics run with limited statistics are discussed, together with prospects for the assessment of the main systematic uncertainties.Comment: 18 pages, 11 figures, contributed to the 10th International Conference on New Frontiers in Physics (ICNFP 2021), 23 August-7 October 2021, Crete, Greec

    Signatures of massive sgoldstinos at hadron colliders

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    In supersymmetric extensions of the Standard Model with a very light gravitino, the effective theory at the weak scale should contain not only the goldstino, but also its supersymmetric partners, the sgoldstinos. In the simplest case, the goldstino is a gauge-singlet and its superpartners are two neutral spin-0 particles, S and P. We study possible signals of massive sgoldstinos at hadron colliders, focusing on those that are most relevant for the Tevatron. We show that inclusive production of sgoldstinos, followed by their decay into two photons, can lead to observable signals or to stringent combined bounds on the gravitino and sgoldstino masses. Sgoldstino decays into two gluon jets may provide a useful complementary signature.Comment: 20 pages, 6 figures. Corrected misprint, added reference

    Signatures of massive sgoldstinos at e+e- colliders

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    In supersymmetric extensions of the Standard Model with a very light gravitino, the effective theory at the weak scale should contain not only the goldstino G, but also its supersymmetric partners, the sgoldstinos. In the simplest case, the goldstino is a gauge-singlet and its superpartners are two neutral spin-0 particles, S and P. We study possible signals of massive sgoldstinos at e+e- colliders, focusing on those that are most relevant at LEP energies. We show that the LEP constraints on e+e- => photon+S (photon+P), Z+S (Z+P) or e+e-S (e+e-P), followed by S (P) decaying into two gluon jets, can lead to stringent combined bounds on the gravitino and sgoldstino masses.Comment: 22 pages, 8 figures. Published version with note adde

    Theoretical predictions for charm and bottom production at the LHC

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    We present predictions for a variety of single-inclusive observables that stem from the production of charm and bottom quark pairs at the 7 TeV LHC. They are obtained within the FONLL semi-analytical framework, and with two "Monte Carlo + NLO" approaches, MC@NLO and POWHEG. Results are given for final states and acceptance cuts that are as close as possible to those used by experimental collaborations and, where feasible, are compared to LHC data.Comment: 22 pages, 10 figure

    Performance of CMS muon reconstruction in pp collision events at sqrt(s) = 7 TeV

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    The performance of muon reconstruction, identification, and triggering in CMS has been studied using 40 inverse picobarns of data collected in pp collisions at sqrt(s) = 7 TeV at the LHC in 2010. A few benchmark sets of selection criteria covering a wide range of physics analysis needs have been examined. For all considered selections, the efficiency to reconstruct and identify a muon with a transverse momentum pT larger than a few GeV is above 95% over the whole region of pseudorapidity covered by the CMS muon system, abs(eta) < 2.4, while the probability to misidentify a hadron as a muon is well below 1%. The efficiency to trigger on single muons with pT above a few GeV is higher than 90% over the full eta range, and typically substantially better. The overall momentum scale is measured to a precision of 0.2% with muons from Z decays. The transverse momentum resolution varies from 1% to 6% depending on pseudorapidity for muons with pT below 100 GeV and, using cosmic rays, it is shown to be better than 10% in the central region up to pT = 1 TeV. Observed distributions of all quantities are well reproduced by the Monte Carlo simulation.Comment: Replaced with published version. Added journal reference and DO

    Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV