52 research outputs found

    A search for new physics in central exclusive production using the missing mass technique with the CMS detector and the CMS-TOTEM precision proton spectrometer

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    A generic search is presented for the associated production of a Z boson or a photon with an additional unspecified massive particle X, pp → pp + Z/γ + X, in proton-tagged events from proton–proton collisions at √s = 13 TeV, recorded in 2017 with the CMS detector and the CMS-TOTEM precision proton spectrometer. The missing mass spectrum is analysed in the 600–1600 GeV range and a fit is performed to search for possible deviations from the background expectation. No significant excess in data with respect to the background predictions has been observed. odelindependent upper limits on the visible production cross section of pp → pp + Z/γ + X are set

    Measurement of the t(t)over-bar production cross section in the all-jet final state in pp collisions at √s=7 TeV

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    This article is the pre-print version of the final published paper that is available from the link below.A measurement is presented of the tt production cross section (σtt) in protonproton collisions at a centre-of-mass energy of 7TeV, in the all-jet final state that contains at least six jets, two of which are tagged as originating from b quarks. The data correspond to an integrated luminosity of 3.54 fb-1, collected with the CMS detector at the LHC. The cross section is determined through an unbinned maximum likelihood fit of background and tt signal to the reconstructed mass spectrum of tt candidates in the data, in which events are subjected to a kinematic fit assuming a tt → W+bW-b → 6 jets hypothesis. The measurement yields σtt = 139±10 (stat.) ±26 (syst.) ±3 (lum.) pb, a result consistent with those obtained in other tt decay channels, as well as with predictions of the standard model

    Endothelial dysfunction and diabetes: roles of hyperglycemia, impaired insulin signaling and obesity

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    Anonymous Women? A Scoping Review of the Experiences of Women in Gamblers Anonymous (GA)

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    Women are participating in gambling at levels approaching those of men, and although levels of disordered gambling remain lower in women than in men, significant numbers are affected. Gamblers Anonymous (GA) is a mainstay of help to problem gamblers in many countries. A scoping review was conducted which specifically addressed the experiences of women who attend GA. Within the 25 identified relevant studies, only two reported empirical data on the specific numbers of women attending. A range of barriers still remain to the participation of women in these communities. These include ‘external’ barriers such as lack of referral and signposting, lack of accessible meetings, and costs of travel; ‘internal’ barriers such as shame, stigma, and fear of disclosure; and features of the GA meetings and discourse, such as a climate which is dismissive of women’s experiences

    Note: Nanosecond LED-based source for optical modeling of scintillators illuminated by partially coherent X-ray radiation

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    We developed a broad-spectrum light source specifically designed to reproduce the temporal behavior of the optical pulses emitted by scintillators for X-ray detection. Nanosecond-to-millisecond pulses are generated through a fast circuit driving Light Emitting Diodes (LEDs) and are endowed with the peculiar time features of the most employed scintillators by means of a dedicated pulse shaping stage. We implement the light source for the optical modeling of the single-shot X-ray coherence measurements with near-field speckles generated by the scattering from colloidal suspensions (heterodyne near field speckle method). Moreover, we derive a rigorous scaling law that quantitatively relates visible and X-ray signal-to-noise ratios

    Electron and photon reconstruction and identification with the CMS experiment at the CERN LHC

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    The performance is presented of the reconstruction and identification algorithms for electrons and photons with the CMS experiment at the LHC. The reported results are based on proton-proton collision data collected at a center-of-mass energy of 13 TeV and recorded in 2016-2018, corresponding to an integrated luminosity of 136 fb(-1). Results obtained from lead-lead collision data collected at root S-NN = 5.02 TeV are also presented. Innovative techniques are used to reconstruct the electron and photon signals in the detector and to optimize the energy resolution. Events with electrons and photons in the final state are used to measure the energy resolution and energy scale uncertainty in the recorded events. The measured energy resolution for electrons produced in Z boson decays in proton-proton collision data ranges from 2 to 5%, depending on electron pseudorapidity and energy loss through bremsstrahlung in the detector material. The energy scale in the same range of energies is measured with an uncertainty smaller than 0.1 (0.3)% in the barrel (endcap) region in proton-proton collisions and better than 1(3)% in the barrel (endcap) region in heavy ion collisions. The timing resolution for electrons from Z boson decays with the full 2016-2018 proton-proton collision data set is measured to be 200 ps

    Performance of the CMS Level-1 trigger in proton-proton collisions at root s=13 TeV

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    At the start of Run 2 in 2015, the LHC delivered proton-proton collisions at a center-ofmass energy of 13 TeV. During Run 2 (years 2015-2018) the LHC eventually reached a luminosity of 2.1 x 10(34) cm(-2) s(-1), almost three times that reached during Run 1 (2009-2013) and a factor of two larger than the LHC design value, leading to events with up to a mean of about 50 simultaneous inelastic proton-proton collisions per bunch crossing (pileup). The CMS Level-1 trigger was upgraded prior to 2016 to improve the selection of physics events in the challenging conditions posed by the second run of the LHC. This paper describes the performance of the CMS Level-1 trigger upgrade during the data taking period of 2016-2018. The upgraded trigger implements pattern recognition and boosted decision tree regression techniques for muon reconstruction, includes pileup subtraction for jets and energy sums, and incorporates pileup-dependent isolation requirements for electrons and tau leptons. In addition, the new trigger calculates high-level quantities such as the invariant mass of pairs of reconstructed particles. The upgrade reduces the trigger rate from background processes and improves the trigger efficiency for a wide variety of physics signals
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