2,473 research outputs found
W and Z studies at CMS
No full textWe present selected measurements done with W and Z bosons detected in the CMS detector, based on samples of events collected during 2011 at 7 TeV and 2012 at 8 TeV physics runs. In this talk, we discuss the measurements of the inclusive W and Z cross sections and the lepton charge asymmetry in the reconstructed W events decaying to a lepton and a neutrino, obtained in the electron and muon decay channels. We also report on the measurements of the differential cross section, forward-backward asymmetry and electroweak couplings of events coming from the Drell-Yan process
Associated production of heavy flavors and W, Z bosons at CMS
No full textThe mechanism of production of heavy-flavoured jets, originated by the hadronization of b or c quarks, in association with vector bosons, W or Z, in the Standard Model is of primary importance. The study of events with one or two well-identified and isolated leptons accompanied by b-jets or displaced secondary vertices is therefore crucial to refine the theoretical calculations in perturbative QCD, as well as validate associated predictions from simulation. The understanding of these processes is furthermore required by Higgs and Beyond the Standard Model searches with similar final states. Using the LHC proton-proton collision data collected at a center of mass energy of 7 TeV by the CMS detector, measurements of the W+b, W+c, Z+b and Z+B hadrons cross sections are presented, comparing experimental data with several theoretical predictions in quantum chromodynamics
Search for Higgs boson pair production with one associated vector boson in proton-proton collisions at sqrt(s) = 13 TeV
No full textA search for Higgs boson pair (HH) production in association with a vector boson V (W or Z boson) is presented. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV, collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb−1. Both hadronic and leptonic decays of V bosons are used. The leptons considered are electrons, muons, and neutrinos. The HH production is searched for in the decay channel. An observed (expected) upper limit at 95% confidence level of VHH production cross section is set at 294 (124) times the standard model prediction. Constraints are also set on the modifiers of the Higgs boson trilinear self-coupling, kλ, assuming k2V = 1, and vice versa on the coupling of two Higgs bosons with two vector bosons, k2V. The observed (expected) 95% confidence intervals of these coupling modifiers are −37.7 < kλ < 37.2 (−30.1 < kλ < 28.9) and −12.2 < k2V < 13.5 (−7.2 < k2V < 8.9), respectively
Constraints on the chiral magnetic effect using charge-dependent azimuthal correlations in pPb and PbPb collisions at the CERN Large Hadron Collider
No full textCharge-dependent azimuthal correlations of same-and opposite-sign pairs with respect to the second-and third-order event planes have been measured in pPb collisions at root s(NN) = 8.16 TeV and PbPb collisions at 5.02 TeV with the CMS experiment at the LHC. The measurement is motivated by the search for the charge separation phenomenon predicted by the chiral magnetic effect (CME) in heavy ion collisions. Three-and two-particle azimuthal correlators are extracted as functions of the pseudorapidity difference, the transverse momentum (p(T)) difference, and the p(T) average of same-and opposite-charge pairs in various event multiplicity ranges. The data suggest that the charge-dependent three-particle correlators with respect to the second-and third-order event planes share a common origin, predominantly arising from charge-dependent two-particle azimuthal correlations coupled with an anisotropic flow. The CME is expected to lead to a v(2)-independent three-particle correlation when the magnetic field is fixed. Using an event shape engineering technique, upper limits on the v(2)-independent fraction of the three-particle correlator are estimated to be 13% for pPb and 7% for PbPb collisions at 95% confidence level. The results of this analysis, both the dominance of two-particle correlations as a source of the three-particle results and the similarities seen between PbPb and pPb, provide stringent constraints on the origin of charge-dependent three-particle azimuthal correlations and challenge their interpretation as arising from a chiral magnetic effect in heavy ion collisions
Search for heavy resonances decaying to Z(nu nu-bar)V(q q'-bar) in proton-proton collisions at sqrt(s) = 13 TeV
No full textA search is presented for heavy bosons decaying to Z(νν ̄)V(qq ̄′), where V can be a W or a Z boson. A sample of proton-proton collision data at s=13 TeV was collected by the CMS experiment during 2016-2018. The data correspond to an integrated luminosity of 137 fb-1. The event categorization is based on the presence of high-momentum jets in the forward region to identify production through weak vector boson fusion. Additional categorization uses jet substructure techniques and the presence of large missing transverse momentum to identify W and Z bosons decaying to quarks and neutrinos, respectively. The dominant standard model backgrounds are estimated using data taken from control regions. The results are interpreted in terms of radion, W′ boson, and graviton models, under the assumption that these bosons are produced via gluon-gluon fusion, Drell-Yan, or weak vector boson fusion processes. No evidence is found for physics beyond the standard model. Upper limits are set at 95% confidence level on various types of hypothetical new bosons. Observed (expected) exclusion limits on the masses of these bosons range from 1.2 to 4.0 (1.1 to 3.7) TeV. © 2022 CERN
Search for dijet resonances in proton-proton collisions at sqrt(s) = 13 TeV and constraints on dark matter and other models
No full textA search is presented for narrow resonances decaying to dijet final states in proton-proton collisions at root s = 13 TeV using data corresponding to an integrated luminosity of 12.9 fb(-1). The dijet mass spectrum is well described by a smooth parameterization and no significant evidence for the production of new particles is observed. Upper limits at 95% confidence level are reported on the production cross section for narrow resonances with masses above 0.6TeV. In the context of specific models, the limits exclude string resonances with masses below 7.4TeV, scalar diquarks below 6.9TeV, axigluons and colorons below 5.5TeV, excited quarks below 5.4TeV, color-octet scalars below 3.OTeV, W' bosons below 2.7 TeV, Z' bosons below 2.1 TeV and between 2.3 and 2.6 TeV, and RS gravitons below 1.9 TeV. These extend previous limits in the dijet channel. Vector and axial-vector mediators in a simplified model of interactions between quarks and dark matter are excluded below 2.0 TeV. The first limits in the dijet channel on dark matter mediators are presented as functions of dark matter mass and are compared to the exclusions of dark matter in direct detection experiments. (C) 2017 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license
Measurement of inclusive jet cross sections in pp and PbPb collisions at sqrt(s_NN) = 2.76 TeV
No full textInclusive jet spectra from pp and PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76TeV, collected with the CMS detector at the CERN Large Hadron Collider, are presented. Jets are reconstructed with three different distance parameters (R=0.2, 0.3, and 0.4) for transverse momentum (pT) greater than 70GeV/c and pseudorapidity |η|<2. Next-to-leading-order quantum chromodynamic calculations with nonperturbative corrections are found to overpredict jet production cross sections in pp for small distance parameters. The jet nuclear modification factors for PbPb compared to pp collisions, show a steady decrease from peripheral to central events, along with a weak dependence on the jet pT. They are found to be independent of the distance parameter in the measured kinematic range. ©2017 CERN, for the CMS Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation
ANGIOPLASTY AND STENTING FOR SYMPTOMATIC ATHEROSCLEROTIC INTACRANIAL STENOSIS: PROCEDURES AND OUTCOME IN 28 CONSECUTIVE PATIENTS WITH 33 INTRACRANIAL STENOSIS
No full textBackground/Objective Elective intracranial stenting with or without balloon angioplasty is an emerging innovative therapy for intracranial vessels stenosis. Few and heterogeneous data about safety and efficacy of this kind of procedure are available. No randomized controlled trial is available. The aim of this paper is to present the experience in stenting and angioplasty on a series of consecutive symptomatic patients with intracranial vessels stenosis. Patients and Methods In the Neuroradiology Department of IRCCS Policlinico Hospital of Milan, from January 2002 to July 2006 a series of 28 consecutive patients, undergone endovascular treatment for 33 symptomatic intracranial vessels stenosis, were evaluated. 22 patients (24 procedures), previously treated using ballon-mounted stent delivery systems for coronary use, were retrospectively reviewed. 7 patients, who were to be treated with self-expanding stent-systems (WingSpan), were prospectively enrolled from March 2006 to July 2006. For each patient we collected data about intra-procedural complications and short-term outcome. The technical success was defined as a residual stenosis of less than 50%. Results 14 internal carotid, 10 vertebral and 9 basilar were treated in 28 patients with recently symptomatic intracranial stenosis >/= 70% on angiography. A technical success was achieved in all cases. No intraprocedural complications were observed. Revascularization led to hemorrhagic complications in two patients. No vessel dissections or ruptures were observed. Three of 28 patients had new neurological symptoms within 24 hours (two transient ischemic attack and one non disabling stroke) and one patient developed a symptomatic basilar thrombosis at 10 days later successfully treated. Conclusions – Endovascular treatment can be performed with a high technical success rate. The procedures were performed with an acceptable complication rate according to literature
Mechanistic Insights of Mitochondrial Dysfunction in Amyotrophic Lateral Sclerosis. An Update on a Lasting Relationship
No full textAmyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of the upper and lower motor neurons. Despite the increasing effort in understanding the etiopathology of ALS, it still remains an obscure disease, and no therapies are currently available to halt its progression. Following the discovery of the first gene associated with familial forms of ALS, Cu–Zn superoxide dismutase, it appeared evident that mitochondria were key elements in the onset of the pathology. However, as more and more ALS-related genes were discovered, the attention shifted from mitochondria impairment to other biological functions such as protein aggregation and RNA metabolism. In recent years, mitochondria have again earned central, mechanistic roles in the pathology, due to accumulating evidence of their derangement in ALS animal models and patients, often resulting in the dysregulation of the energetic metabolism. In this review, we first provide an update of the last lustrum on the molecular mechanisms by which the most well-known ALS-related proteins affect mitochondrial functions and cellular bioenergetics. Next, we focus on evidence gathered from human specimens and advance the concept of a cellular-specific mitochondrial “metabolic threshold”, which may appear pivotal in ALS pathogenesis
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