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Significant enhancement of ferromagnetism above room temperature in epitaxial 2D van der Waals ferromagnet Fe 5-δGeTe 2/Bi 2Te 3 heterostructures. NANOSCALE 2023; 15:2223-2233. [PMID: 36625389 DOI: 10.1039/d2nr04820e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Two-dimensional (2D) van der Waals (vdW) ferromagnetic metals FexGeTe2 with x = 3-5 have raised significant interest in the scientific community. Fe5GeTe2 shows prospects for spintronic applications since the Curie temperature Tc has been reported near or higher than 300 K. In the present work, epitaxial Fe5-δGeTe2 (FGT) heterostructures were grown by Molecular Beam Epitaxy (MBE) on insulating crystalline substrates. The FGT films were combined with Bi2Te3 topological insulator (TI) aiming to investigate the possible beneficial effect of the TI on the magnetic properties of FGT. FGT/Bi2Te3 films were compared to FGT capped only with AlOx to prevent oxidation. SQUID and MOKE measurements revealed that the growth of Bi2Te3 TI on FGT films significantly enhances the saturation magnetization of FGT as well as the Tc well above room temperature (RT) reaching record values of 570 K. First-principles calculations predict a shift of the Fermi level and an associated enhancement of the majority spin (primarily) as well as the total density of states at the Fermi level suggesting that effective doping of FGT from Bi2Te3 could explain the enhancement of ferromagnetism in FGT. It is also predicted that strain induced stabilization of a high magnetic moment phase in FGT/Bi2Te3 could be an alternative explanation of magnetization and Tc enhancement. Ferromagnetic resonance measurements evidence an enhanced broadening in the FGT/Bi2Te3 heterostructure when compared to FGT. We obtain a large spin mixing conductance of g↑↓eff = 4.4 × 1020 m-2, which demonstrates the great potential of FGT/Bi2Te3 systems for spin-charge conversion applications at room temperature.
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Metabolism-Related Gene Expression in Circulating Tumor Cells from Patients with Early Stage Non-Small Cell Lung Cancer. Cancers (Basel) 2022; 14:cancers14133237. [PMID: 35805008 PMCID: PMC9264894 DOI: 10.3390/cancers14133237] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 06/23/2022] [Accepted: 06/27/2022] [Indexed: 11/25/2022] Open
Abstract
Simple Summary In the present study, the expression of three Metabolism-Related Enzymes (MRGs) that are related to glucose and pyruvate metabolism, in parallel with glucose and monocarboxylate transporter expression (HK2, MCT1, PHGDH), was studied in CTCs isolated from the peripheral blood of early stage NSCLC patients at different timepoints. The expression levels of all tested MRGs decreased in CTCs one month after surgery, but a significant increase was noticed at the time of relapse for PHGDH and MCT1 only. An overexpression of MRGs was observed at a high frequency in the CTCs isolated from early NSCLC patients, thereby supporting the role of MRGs in metastatic processes. The glycolytic and mesenchymal subpopulation of CTCs was significantly predominant compared to CTCs that wereglycolytic but not mesenchymal-like. Our data indicate that MRGs merit further evaluation through large and well-defined cohort studies. Abstract Purpose: Metabolic reprogramming is now characterized as one of the core hallmarks of cancer, and it has already been shown that the altered genomic profile of metabolically rewired cancer cells can give valuable information. In this study, we quantified three Metabolism-Related Gene (MRG) transcripts in the circulating tumor cells (CTCs) of early stage NSCLC patients and evaluated their associations with epithelial and EMT markers. Experimental Design: We first developed and analytically validated highly sensitive RT-qPCR assays for the quantification of HK2, MCT1 and PHGDH transcripts, and further studied the expression of MRGs in CTCs that were isolated using a size-dependent microfluidic device (Parsortix, Angle) from the peripheral blood of: (a) 46 NSCLC patients at baseline, (b) 39/46 of these patients one month after surgery, (c) 10/46 patients at relapse and (d) 10 pairs of cancerous and adjacent non-cancerous FFPE tissues from the same NSCLC patients. Epithelial and EMT markers were also evaluated. Results: MCT1 and HK2 were differentially expressed between HD and NSCLC patients. An overexpression of MCT1 was detected in 15/46 (32.6%) and 3/10 (30%) patients at baseline and at progression disease (PD), respectively, whereas an overexpression of HK2 was detected in 30.4% and 0% of CTCs in the same group of samples. The expression levels of all tested MRGs decreased in CTCs one month after surgery, but a significant increase was noticed at the time of relapse for PHGDH and MCT1 only. The expression levels of HK2 and MCT1 were associated with the overexpression of mesenchymal markers (TWIST-1 and VIM). Conclusion: An overexpression of MRGs was observed at a high frequency in the CTCs isolated from early NSCLC patients, thereby supporting the role of MRGs in metastatic processes. The glycolytic and mesenchymal subpopulation of CTCs was significantly predominant compared to CTCs that were glycolytic but not mesenchymal-like. Our data indicate that MRGs merit further evaluation through large and well-defined cohort studies.
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Abstract
The quantum Hall effect (QHE) is traditionally considered to be a purely two-dimensional (2D) phenomenon. Recently, however, a three-dimensional (3D) version of the QHE was reported in the Dirac semimetal ZrTe5. It was proposed to arise from a magnetic-field-driven Fermi surface instability, transforming the original 3D electron system into a stack of 2D sheets. Here, we report thermodynamic, spectroscopic, thermoelectric and charge transport measurements on such ZrTe5 samples. The measured properties: magnetization, ultrasound propagation, scanning tunneling spectroscopy, and Raman spectroscopy, show no signatures of a Fermi surface instability, consistent with in-field single crystal X-ray diffraction. Instead, a direct comparison of the experimental data with linear response calculations based on an effective 3D Dirac Hamiltonian suggests that the quasi-quantization of the observed Hall response emerges from the interplay of the intrinsic properties of the ZrTe5 electronic structure and its Dirac-type semi-metallic character.
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14P Studying tumour heterogeneity of primary non-small cell lung cancer in humans and mice (PDX). J Thorac Oncol 2021. [DOI: 10.1016/s1556-0864(21)01856-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
Interacting electrons confined to their lowest Landau level in a high magnetic field can form a variety of correlated states, some of which manifest themselves in a Hall effect. Although such states have been predicted to occur in three-dimensional semimetals, a corresponding Hall response has not yet been experimentally observed. Here, we report the observation of an unconventional Hall response in the quantum limit of the bulk semimetal HfTe5, adjacent to the three-dimensional quantum Hall effect of a single electron band at low magnetic fields. The additional plateau-like feature in the Hall conductivity of the lowest Landau level is accompanied by a Shubnikov-de Haas minimum in the longitudinal electrical resistivity and its magnitude relates as 3/5 to the height of the last plateau of the three-dimensional quantum Hall effect. Our findings are consistent with strong electron-electron interactions, stabilizing an unconventional variant of the Hall effect in a three-dimensional material in the quantum limit.
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Nicotine withdrawal-induced inattention is absent in alpha7 nAChR knockout mice. Psychopharmacology (Berl) 2017; 234:1573-1586. [PMID: 28243714 PMCID: PMC5420484 DOI: 10.1007/s00213-017-4572-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 02/15/2017] [Indexed: 11/25/2022]
Abstract
RATIONALE Smoking is the leading cause of preventable death in the USA, but quit attempts result in withdrawal-induced cognitive dysfunction and predicts relapse. Greater understanding of the neural mechanism(s) underlying these cognitive deficits is required to develop targeted treatments to aid quit attempts. OBJECTIVES We examined nicotine withdrawal-induced inattention in mice lacking the α7 nicotinic acetylcholine receptor (nAChR) using the five-choice continuous performance test (5C-CPT). METHODS Mice were trained in the 5C-CPT prior to osmotic minipump implantation containing saline or nicotine. Experiment 1 used 40 mg kg-1 day-1 nicotine treatment and tested C57BL/6 mice 4, 28, and 52 h after pump removal. Experiment 2 used 14 and 40 mg kg-1 day-1 nicotine treatment in α7 nAChR knockout (KO) and wildtype (WT) littermates tested 4 h after pump removal. Subsets of WT mice were killed before and after pump removal to assess changes in receptor expression associated with nicotine administration and withdrawal. RESULTS Nicotine withdrawal impaired attention in the 5C-CPT, driven by response inhibition and target detection deficits. The overall attentional deficit was absent in α7 nAChR KO mice despite response disinhibition in these mice. Synaptosomal glutamate mGluR5 and dopamine D4 receptor expression were reduced during chronic nicotine but increased during withdrawal, potentially contributing to cognitive deficits. CONCLUSIONS The α7 nAChR may underlie nicotine withdrawal-induced deficits in target detection but is not required for response disinhibition deficits. Alterations to the glutamatergic and dopaminergic pathways may also contribute to withdrawal-induced attentional deficits, providing novel targets to alleviate the cognitive symptoms of withdrawal during quit attempts.
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Postnatal Phencyclidine (PCP) as a Neurodevelopmental Animal Model of Schizophrenia Pathophysiology and Symptomatology: A Review. Curr Top Behav Neurosci 2016; 29:403-428. [PMID: 26510740 DOI: 10.1007/7854_2015_403] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Cognitive dysfunction and negative symptoms of schizophrenia remain an unmet clinical need. Therefore, it is essential that new treatments and approaches are developed to recover the cognitive and social impairments that are seen in patients with schizophrenia. These may only be discovered through the use of carefully validated, aetiologically relevant and translational animal models. With recent renewed interest in the neurodevelopmental hypothesis of schizophrenia, postnatal administration of N-methyl-D-aspartate receptor (NMDAR) antagonists such as phencyclidine (PCP) has been proposed as a model that can mimic aspects of schizophrenia pathophysiology. The purpose of the current review is to examine the validity of this model and compare it with the adult subchronic PCP model. We review the ability of postnatal PCP administration to produce behaviours (specifically cognitive deficits) and neuropathology of relevance to schizophrenia and their subsequent reversal by pharmacological treatments. We review studies investigating effects of postnatal PCP on cognitive domains in schizophrenia in rats. Morris water maze and delayed spontaneous alternation tasks have been used for working memory, attentional set-shifting for executive function, social novelty discrimination for selective attention and prepulse inhibition of acoustic startle for sensorimotor gating. In addition, we review studies on locomotor activity and neuropathology. We also include two studies using dual hit models incorporating postnatal PCP and two studies on social behaviour deficits following postnatal PCP. Overall, the evidence we provide supports the use of postnatal PCP to model cognitive and neuropathological disturbances of relevance to schizophrenia. To date, there is a lack of evidence to support a significant advantage of postnatal PCP over the adult subchronic PCP model and full advantage has not been taken of its neurodevelopmental component. When thoroughly characterised, it is likely that it will provide a useful neurodevelopmental model to complement other models such as maternal immune activation, particularly when combined with other manipulations to produce dual or triple hit models. However, the developmental trajectory of behavioural and neuropathological changes induced by postnatal PCP and their relevance to schizophrenia must be carefully mapped out. Overall, we support further development of dual (or triple) hit models incorporating genetic, neurodevelopmental and appropriate environmental elements in the search for more aetiologically valid animal models of schizophrenia and neurodevelopmental disorders (NDDs).
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Measurement of the differential cross section for top quark pair production in pp collisions at [Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2015; 75:542. [PMID: 26640401 PMCID: PMC4657759 DOI: 10.1140/epjc/s10052-015-3709-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2015] [Accepted: 09/29/2015] [Indexed: 05/22/2023]
Abstract
The normalized differential cross section for top quark pair ([Formula: see text]) production is measured in pp collisions at a centre-of-mass energy of 8[Formula: see text] at the CERN LHC using the CMS detector in data corresponding to an integrated luminosity of 19.7[Formula: see text]. The measurements are performed in the lepton[Formula: see text]jets ([Formula: see text][Formula: see text]jets) and in the dilepton ([Formula: see text], [Formula: see text], and [Formula: see text]) decay channels. The [Formula: see text] cross section is measured as a function of the kinematic properties of the charged leptons, the jets associated to b quarks, the top quarks, and the [Formula: see text] system. The data are compared with several predictions from perturbative quantum chromodynamic up to approximate next-to-next-to-leading-order precision. No significant deviations are observed relative to the standard model predictions.
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Measurements of the [Formula: see text][Formula: see text] production cross sections in the [Formula: see text] channel in proton-proton collisions at [Formula: see text] and [Formula: see text] and combined constraints on triple gauge couplings. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2015; 75:511. [PMID: 26549982 PMCID: PMC4627252 DOI: 10.1140/epjc/s10052-015-3706-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 09/25/2015] [Indexed: 06/05/2023]
Abstract
Measurements of the [Formula: see text][Formula: see text] production cross sections in proton-proton collisions at center-of-mass energies of 7 and 8[Formula: see text] are presented. Candidate events for the leptonic decay mode [Formula: see text], where [Formula: see text] denotes an electron or a muon, are reconstructed and selected from data corresponding to an integrated luminosity of 5.1 (19.6)[Formula: see text] at 7 (8)[Formula: see text] collected with the CMS experiment. The measured cross sections, [Formula: see text] at 7[Formula: see text], and [Formula: see text] at 8[Formula: see text], are in good agreement with the standard model predictions with next-to-leading-order accuracy. The selected data are analyzed to search for anomalous triple gauge couplings involving the [Formula: see text][Formula: see text] final state. In the absence of any deviation from the standard model predictions, limits are set on the relevant parameters. These limits are then combined with the previously published CMS results for [Formula: see text][Formula: see text] in 4[Formula: see text] final states, yielding the most stringent constraints on the anomalous couplings.
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Disruption of mGluR5 in parvalbumin-positive interneurons induces core features of neurodevelopmental disorders. Mol Psychiatry 2015; 20:1161-72. [PMID: 26260494 PMCID: PMC4583365 DOI: 10.1038/mp.2015.113] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2014] [Revised: 06/21/2015] [Accepted: 07/06/2015] [Indexed: 12/13/2022]
Abstract
Alterations in glutamatergic transmission onto developing GABAergic systems, in particular onto parvalbumin-positive (Pv(+)) fast-spiking interneurons, have been proposed as underlying causes of several neurodevelopmental disorders, including schizophrenia and autism. Excitatory glutamatergic transmission, through ionotropic and metabotropic glutamate receptors, is necessary for the correct postnatal development of the Pv(+) GABAergic network. We generated mutant mice in which the metabotropic glutamate receptor 5 (mGluR5) was specifically ablated from Pv(+) interneurons postnatally, and investigated the consequences of such a manipulation at the cellular, network and systems levels. Deletion of mGluR5 from Pv(+) interneurons resulted in reduced numbers of Pv(+) neurons and decreased inhibitory currents, as well as alterations in event-related potentials and brain oscillatory activity. These cellular and sensory changes translated into domain-specific memory deficits and increased compulsive-like behaviors, abnormal sensorimotor gating and altered responsiveness to stimulant agents. Our findings suggest a fundamental role for mGluR5 in the development of Pv(+) neurons and show that alterations in this system can produce broad-spectrum alterations in brain network activity and behavior that are relevant to neurodevelopmental disorders.
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Constraints on the pMSSM, AMSB model and on other models from the search for long-lived charged particles in proton-proton collisions at [Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2015; 75:325. [PMID: 26213486 PMCID: PMC4509674 DOI: 10.1140/epjc/s10052-015-3533-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 06/19/2015] [Indexed: 06/10/2023]
Abstract
Stringent limits are set on the long-lived lepton-like sector of the phenomenological minimal supersymmetric standard model (pMSSM) and the anomaly-mediated supersymmetry breaking (AMSB) model. The limits are derived from the results presented in a recent search for long-lived charged particles in proton-proton collisions, based on data collected by the CMS detector at a centre-of-mass energy of 8 TeV at the Large Hadron Collider. In the pMSSM parameter sub-space considered, 95.9 % of the points predicting charginos with a lifetime of at least 10 ns are excluded. These constraints on the pMSSM are the first obtained at the LHC. Charginos with a lifetime greater than 100 ns and masses up to about 800 GeV in the AMSB model are also excluded. The method described can also be used to set constraints on other models.
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Evidence for Collective Multiparticle Correlations in p-Pb Collisions. PHYSICAL REVIEW LETTERS 2015; 115:012301. [PMID: 26182092 DOI: 10.1103/physrevlett.115.012301] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Indexed: 06/04/2023]
Abstract
The second-order azimuthal anisotropy Fourier harmonics, v2, are obtained in p-Pb and PbPb collisions over a wide pseudorapidity (η) range based on correlations among six or more charged particles. The p-Pb data, corresponding to an integrated luminosity of 35 nb-1, were collected during the 2013 LHC p-Pb run at a nucleon-nucleon center-of-mass energy of 5.02 TeV by the CMS experiment. A sample of semiperipheral PbPb collision data at √sNN=2.76 TeV, corresponding to an integrated luminosity of 2.5 μb-1 and covering a similar range of particle multiplicities as the p-Pb data, is also analyzed for comparison. The six- and eight-particle cumulant and the Lee-Yang zeros methods are used to extract the v2 coefficients, extending previous studies of two- and four-particle correlations. For both the p-Pb and PbPb systems, the v2 values obtained with correlations among more than four particles are consistent with previously published four-particle results. These data support the interpretation of a collective origin for the previously observed long-range (large Δη) correlations in both systems. The ratios of v2 values corresponding to correlations including different numbers of particles are compared to theoretical predictions that assume a hydrodynamic behavior of a p-Pb system dominated by fluctuations in the positions of participant nucleons. These results provide new insights into the multiparticle dynamics of collision systems with a very small overlapping region.
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Distributions of topological observables in inclusive three- and four-jet events in pp collisions at [Formula: see text][Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2015; 75:302. [PMID: 26190937 PMCID: PMC4498646 DOI: 10.1140/epjc/s10052-015-3491-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 06/02/2015] [Indexed: 06/04/2023]
Abstract
This paper presents distributions of topological observables in inclusive three- and four-jet events produced in pp collisions at a centre-of-mass energy of 7[Formula: see text] with a data sample collected by the CMS experiment corresponding to a luminosity of 5.1[Formula: see text]. The distributions are corrected for detector effects, and compared with several event generators based on two- and multi-parton matrix elements at leading order. Among the considered calculations, MadGraph interfaced with pythia6 displays the overall best agreement with data.
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Constraints on parton distribution functions and extraction of the strong coupling constant from the inclusive jet cross section in pp collisions at [Formula: see text][Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2015; 75:288. [PMID: 26146483 PMCID: PMC4482490 DOI: 10.1140/epjc/s10052-015-3499-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 06/02/2015] [Indexed: 06/01/2023]
Abstract
The inclusive jet cross section for proton-proton collisions at a centre-of-mass energy of 7[Formula: see text] was measured by the CMS Collaboration at the LHC with data corresponding to an integrated luminosity of 5.0[Formula: see text]. The measurement covers a phase space up to 2[Formula: see text] in jet transverse momentum and 2.5 in absolute jet rapidity. The statistical precision of these data leads to stringent constraints on the parton distribution functions of the proton. The data provide important input for the gluon density at high fractions of the proton momentum and for the strong coupling constant at large energy scales. Using predictions from perturbative quantum chromodynamics at next-to-leading order, complemented with electroweak corrections, the constraining power of these data is investigated and the strong coupling constant at the Z boson mass [Formula: see text] is determined to be [Formula: see text], which is in agreement with the world average.
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Search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks using a matrix element method. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2015; 75:251. [PMID: 26097407 PMCID: PMC4464697 DOI: 10.1140/epjc/s10052-015-3454-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 05/11/2015] [Indexed: 05/28/2023]
Abstract
A search for a standard model Higgs boson produced in association with a top-quark pair and decaying to bottom quarks is presented. Events with hadronic jets and one or two oppositely charged leptons are selected from a data sample corresponding to an integrated luminosity of 19.5[Formula: see text] collected by the CMS experiment at the LHC in [Formula: see text] collisions at a centre-of-mass energy of 8[Formula: see text]. In order to separate the signal from the larger [Formula: see text] + jets background, this analysis uses a matrix element method that assigns a probability density value to each reconstructed event under signal or background hypotheses. The ratio between the two values is used in a maximum likelihood fit to extract the signal yield. The results are presented in terms of the measured signal strength modifier, [Formula: see text], relative to the standard model prediction for a Higgs boson mass of 125[Formula: see text]. The observed (expected) exclusion limit at a 95 % confidence level is [Formula: see text] (3.3), corresponding to a best fit value [Formula: see text].
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Search for dark matter, extra dimensions, and unparticles in monojet events in proton-proton collisions at [Formula: see text][Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2015; 75:235. [PMID: 26069461 PMCID: PMC4455910 DOI: 10.1140/epjc/s10052-015-3451-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 05/11/2015] [Indexed: 06/02/2023]
Abstract
Results are presented from a search for particle dark matter (DM), extra dimensions, and unparticles using events containing a jet and an imbalance in transverse momentum. The data were collected by the CMS detector in proton-proton collisions at the LHC and correspond to an integrated luminosity of 19.7[Formula: see text]at a centre-of-mass energy of 8[Formula: see text]. The number of observed events is found to be consistent with the standard model prediction. Limits are placed on the DM-nucleon scattering cross section as a function of the DM particle mass for spin-dependent and spin-independent interactions. Limits are also placed on the scale parameter [Formula: see text] in the Arkani-Hamed, Dimopoulos, and Dvali (ADD) model of large extra dimensions, and on the unparticle model parameter [Formula: see text]. The constraints on ADD models and unparticles are the most stringent limits in this channel and those on the DM-nucleon scattering cross section are an improvement over previous collider results.
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Nuclear effects on the transverse momentum spectra of charged particles in pPb collisions at [Formula: see text][Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2015; 75:237. [PMID: 26069462 PMCID: PMC4455909 DOI: 10.1140/epjc/s10052-015-3435-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 05/01/2015] [Indexed: 06/04/2023]
Abstract
Transverse momentum spectra of charged particles are measured by the CMS experiment at the CERN LHC in pPb collisions at [Formula: see text][Formula: see text], in the range [Formula: see text][Formula: see text] and pseudorapidity [Formula: see text] in the proton-nucleon center-of-mass frame. For [Formula: see text][Formula: see text], the charged-particle production is asymmetric about [Formula: see text], with smaller yield observed in the direction of the proton beam, qualitatively consistent with expectations from shadowing in nuclear parton distribution functions (nPDF). A pp reference spectrum at [Formula: see text][Formula: see text] is obtained by interpolation from previous measurements at higher and lower center-of-mass energies. The [Formula: see text] distribution measured in pPb collisions shows an enhancement of charged particles with [Formula: see text][Formula: see text] compared to expectations from the pp reference. The enhancement is larger than predicted by perturbative quantum chromodynamics calculations that include antishadowing modifications of nPDFs.
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Measurement of J/ψ and ψ(2S) Prompt Double-Differential Cross Sections in pp Collisions at sqrt[s]=7 TeV. PHYSICAL REVIEW LETTERS 2015; 114:191802. [PMID: 26024161 DOI: 10.1103/physrevlett.114.191802] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Indexed: 06/04/2023]
Abstract
The double-differential cross sections of promptly produced J/ψ and ψ(2S) mesons are measured in pp collisions at sqrt[s]=7 TeV, as a function of transverse momentum p_{T} and absolute rapidity |y|. The analysis uses J/ψ and ψ(2S) dimuon samples collected by the CMS experiment, corresponding to integrated luminosities of 4.55 and 4.90 fb^{-1}, respectively. The results are based on a two-dimensional analysis of the dimuon invariant mass and decay length, and extend to p_{T}=120 and 100 GeV for the J/ψ and ψ(2S), respectively, when integrated over the interval |y|<1.2. The ratio of the ψ(2S) to J/ψ cross sections is also reported for |y|<1.2, over the range 10<p_{T}<100 GeV. These are the highest p_{T} values for which the cross sections and ratio have been measured.
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Precise determination of the mass of the Higgs boson and tests of compatibility of its couplings with the standard model predictions using proton collisions at 7 and 8[Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2015; 75:212. [PMID: 25999783 PMCID: PMC4433454 DOI: 10.1140/epjc/s10052-015-3351-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Accepted: 03/09/2015] [Indexed: 05/28/2023]
Abstract
Properties of the Higgs boson with mass near 125[Formula: see text] are measured in proton-proton collisions with the CMS experiment at the LHC. Comprehensive sets of production and decay measurements are combined. The decay channels include [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] pairs. The data samples were collected in 2011 and 2012 and correspond to integrated luminosities of up to 5.1[Formula: see text] at 7[Formula: see text] and up to 19.7[Formula: see text] at 8[Formula: see text]. From the high-resolution [Formula: see text] and [Formula: see text] channels, the mass of the Higgs boson is determined to be [Formula: see text]. For this mass value, the event yields obtained in the different analyses tagging specific decay channels and production mechanisms are consistent with those expected for the standard model Higgs boson. The combined best-fit signal relative to the standard model expectation is [Formula: see text] at the measured mass. The couplings of the Higgs boson are probed for deviations in magnitude from the standard model predictions in multiple ways, including searches for invisible and undetected decays. No significant deviations are found.
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Measurement of the inclusive 3-jet production differential cross section in proton-proton collisions at 7 TeV and determination of the strong coupling constant in the TeV range. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2015; 75:186. [PMID: 25983654 PMCID: PMC4423910 DOI: 10.1140/epjc/s10052-015-3376-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 03/27/2015] [Indexed: 06/04/2023]
Abstract
This paper presents a measurement of the inclusive 3-jet production differential cross section at a proton-proton centre-of-mass energy of 7 TeV using data corresponding to an integrated luminosity of 5[Formula: see text]collected with the CMS detector. The analysis is based on the three jets with the highest transverse momenta. The cross section is measured as a function of the invariant mass of the three jets in a range of 445-3270 GeV and in two bins of the maximum rapidity of the jets up to a value of 2. A comparison between the measurement and the prediction from perturbative QCD at next-to-leading order is performed. Within uncertainties, data and theory are in agreement. The sensitivity of the observable to the strong coupling constant [Formula: see text] is studied. A fit to all data points with 3-jet masses larger than 664 GeV gives a value of the strong coupling constant of [Formula: see text].
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22
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Search for decays of stopped long-lived particles produced in proton-proton collisions at [Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2015; 75:151. [PMID: 25983648 PMCID: PMC4423862 DOI: 10.1140/epjc/s10052-015-3367-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 03/19/2015] [Indexed: 06/04/2023]
Abstract
A search has been performed for long-lived particles that could have come to rest within the CMS detector, using the time intervals between LHC beam crossings. The existence of such particles could be deduced from observation of their decays via energy deposits in the CMS calorimeter appearing at times that are well separated from any proton-proton collisions. Using a data set corresponding to an integrated luminosity of 18.6[Formula: see text] of 8[Formula: see text] proton-proton collisions, and a search interval corresponding to 281 h of trigger livetime, 10 events are observed, with a background prediction of [Formula: see text] events. Limits are presented at 95 % confidence level on gluino and top squark production, for over 13 orders of magnitude in the mean proper lifetime of the stopped particle. Assuming a cloud model of R-hadron interactions, a gluino with mass [Formula: see text]1000[Formula: see text] and a top squark with mass [Formula: see text]525[Formula: see text] are excluded, for lifetimes between 1 [Formula: see text]s and 1000[Formula: see text]. These results are the most stringent constraints on stopped particles to date.
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23
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Measurements of differential and double-differential Drell-Yan cross sections in proton-proton collisions at [Formula: see text][Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2015; 75:147. [PMID: 26041973 PMCID: PMC4446050 DOI: 10.1140/epjc/s10052-015-3364-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 03/19/2015] [Indexed: 05/22/2023]
Abstract
Measurements of the differential and double-differential Drell-Yan cross sections in the dielectron and dimuon channels are presented. They are based on proton-proton collision data at [Formula: see text] recorded with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7[Formula: see text]. The measured inclusive cross section in the [Formula: see text] peak region (60-120[Formula: see text]), obtained from the combination of the dielectron and dimuon channels, is [Formula: see text], where the statistical uncertainty is negligible. The differential cross section [Formula: see text] in the dilepton mass range 15-2000[Formula: see text] is measured and corrected to the full phase space. The double-differential cross section [Formula: see text] is also measured over the mass range 20 to 1500[Formula: see text] and absolute dilepton rapidity from 0 to 2.4. In addition, the ratios of the normalized differential cross sections measured at [Formula: see text] and 8[Formula: see text] are presented. These measurements are compared to the predictions of perturbative QCD at next-to-leading and next-to-next-to-leading (NNLO) orders using various sets of parton distribution functions (PDFs). The results agree with the NNLO theoretical predictions computed with fewz 3.1 using the CT10 NNLO and NNPDF2.1 NNLO PDFs. The measured double-differential cross section and ratio of normalized differential cross sections are sufficiently precise to constrain the proton PDFs.
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24
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Search for supersymmetry using razor variables in events withb-tagged jets inppcollisions ats=8 TeV. Int J Clin Exp Med 2015. [DOI: 10.1103/physrevd.91.052018] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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25
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Search for long-lived particles that decay into final states containing two electrons or two muons in proton-proton collisions ats=8 TeV. Int J Clin Exp Med 2015. [DOI: 10.1103/physrevd.91.052012] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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26
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Search for monotop signatures in proton-proton collisions at √s=8 TeV. PHYSICAL REVIEW LETTERS 2015; 114:101801. [PMID: 25815923 DOI: 10.1103/physrevlett.114.101801] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2014] [Indexed: 06/04/2023]
Abstract
Results are presented from a search for new decaying massive particles whose presence is inferred from an imbalance in transverse momentum and which are produced in association with a single top quark that decays into a bottom quark and two light quarks. The measurement is performed using 19.7 fb^{-1} of data from proton-proton collisions at a center-of-mass energy of 8 TeV, collected with the CMS detector at the CERN LHC. No deviations from the standard model predictions are observed and lower limits are set on the masses of new invisible bosons. In particular, scalar and vector particles, with masses below 330 and 650 GeV, respectively, are excluded at 95% confidence level, thereby substantially extending a previous limit published by the CDF Collaboration.
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27
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Search for displaced supersymmetry in events with an electron and a muon with large impact parameters. PHYSICAL REVIEW LETTERS 2015; 114:061801. [PMID: 25723204 DOI: 10.1103/physrevlett.114.061801] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Indexed: 06/04/2023]
Abstract
A search for new long-lived particles decaying to leptons is presented using proton-proton collisions produced by the LHC at √[s]=8 TeV. Data used for the analysis were collected by the CMS detector and correspond to an integrated luminosity of 19.7 fb(-1). Events are selected with an electron and muon with opposite charges that both have transverse impact parameter values between 0.02 and 2 cm. The search has been designed to be sensitive to a wide range of models with nonprompt e-μ final states. Limits are set on the "displaced supersymmetry" model, with pair production of top squarks decaying into an e-μ final state via R-parity-violating interactions. The results are the most restrictive to date on this model, with the most stringent limit being obtained for a top squark lifetime corresponding to cτ=2 cm, excluding masses below 790 GeV at 95% confidence level.
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Measurement of electroweak production of two jets in association with a Z boson in proton-proton collisions at [Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2015; 75:66. [PMID: 25838791 PMCID: PMC4376472 DOI: 10.1140/epjc/s10052-014-3232-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Accepted: 12/15/2014] [Indexed: 06/01/2023]
Abstract
The purely electroweak (EW) cross section for the production of two jets in association with a Z boson, in proton-proton collisions at [Formula: see text], is measured using data recorded by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 19.7[Formula: see text]. The electroweak cross section for the [Formula: see text] final state (with [Formula: see text] or [Formula: see text] and j representing the quarks produced in the hard interaction) in the kinematic region defined by [Formula: see text][Formula: see text], [Formula: see text][Formula: see text], transverse momentum [Formula: see text][Formula: see text], and pseudorapidity [Formula: see text], is found to be [Formula: see text], in agreement with the standard model prediction. The associated jet activity of the selected events is studied, in particular in a signal-enriched region of phase space, and the measurements are found to be in agreement with QCD predictions.
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29
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Study of vector boson scattering and search for new physics in events with two same-sign leptons and two jets. PHYSICAL REVIEW LETTERS 2015; 114:051801. [PMID: 25699433 DOI: 10.1103/physrevlett.114.051801] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Indexed: 05/23/2023]
Abstract
A study of vector boson scattering in pp collisions at a center-of-mass energy of 8 TeV is presented. The data sample corresponds to an integrated luminosity of 19.4 fb(-1) collected with the CMS detector. Candidate events are selected with exactly two leptons of the same charge, two jets with large rapidity separation and high dijet mass, and moderate missing transverse energy. The signal region is expected to be dominated by electroweak same-sign W-boson pair production. The observation agrees with the standard model prediction. The observed significance is 2.0 standard deviations, where a significance of 3.1 standard deviations is expected based on the standard model. Cross section measurements for W(±)W(±) and WZ processes in the fiducial region are reported. Bounds on the structure of quartic vector-boson interactions are given in the framework of dimension-eight effective field theory operators, as well as limits on the production of doubly charged Higgs bosons.
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30
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Measurement of prompt ψ(2S) to J/ψ yield ratios in Pb-Pb and p-p collisions at sqrt[sNN]=2.76 TeV. PHYSICAL REVIEW LETTERS 2014; 113:262301. [PMID: 25615312 DOI: 10.1103/physrevlett.113.262301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Indexed: 06/04/2023]
Abstract
The ratio between the prompt ψ(2S) and J/ψ yields, reconstructed via their decays into μ+ μ-, is measured in Pb-Pb and p-p collisions at sqrt[sNN]=2.76 TeV. The analysis is based on Pb-Pb and p-p data samples collected by CMS at the Large Hadron Collider, corresponding to integrated luminosities of 150 μb(-1) and 5.4 pb(-1), respectively. The double ratio of measured yields (Nψ(2S)/N(J/ψ))(Pb-Pb)/(Nψ(2S)/N(J/ψ))(p-p) is computed in three Pb-Pb collision centrality bins and two kinematic ranges: one at midrapidity, |y|<1.6, covering the transverse momentum range 6.5<pT<30 GeV/c, and the other at forward rapidity, 1.6<|y|<2.4, extending to lower pT values, 3<pT<30 GeV/c. The centrality-integrated double ratio changes from 0.45±0.13(stat)±0.07(syst) in the first range to 1.67±0.34(stat)±0.27(syst) in the second. This difference is most pronounced in the most central collisions.
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31
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Searches for heavy Higgs bosons in two-Higgs-doublet models and fort→chdecay using multilepton and diphoton final states inppcollisions at 8 TeV. Int J Clin Exp Med 2014. [DOI: 10.1103/physrevd.90.112013] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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32
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33
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Search for heavy neutrinos and [Formula: see text] bosons with right-handed couplings in proton-proton collisions at [Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2014; 74:3149. [PMID: 25814876 PMCID: PMC4371073 DOI: 10.1140/epjc/s10052-014-3149-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 10/22/2014] [Indexed: 06/04/2023]
Abstract
A search for heavy, right-handed neutrinos, [Formula: see text] ([Formula: see text]), and right-handed [Formula: see text] bosons, which arise in the left-right symmetric extensions of the standard model, has been performed by the CMS experiment. The search was based on a sample of two lepton plus two jet events collected in proton-proton collisions at a center-of-mass energy of 8[Formula: see text] corresponding to an integrated luminosity of 19.7 [Formula: see text]. For models with strict left-right symmetry, and assuming only one [Formula: see text] flavor contributes significantly to the [Formula: see text] decay width, the region in the two-dimensional [Formula: see text] mass plane excluded at a 95 % confidence level extends to approximately [Formula: see text] and covers a large range of neutrino masses below the [Formula: see text] boson mass, depending on the value of [Formula: see text]. This search significantly extends the [Formula: see text] exclusion region beyond previous results.
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34
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Measurement of differential cross sections for the production of a pair of isolated photons in pp collisions at [Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2014; 74:3129. [PMID: 25814874 PMCID: PMC4371070 DOI: 10.1140/epjc/s10052-014-3129-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 10/14/2014] [Indexed: 06/04/2023]
Abstract
A measurement of differential cross sections for the production of a pair of isolated photons in proton-proton collisions at [Formula: see text] is presented. The data sample corresponds to an integrated luminosity of 5.0[Formula: see text] collected with the CMS detector. A data-driven isolation template method is used to extract the prompt diphoton yield. The measured cross section for two isolated photons, with transverse energy above 40 and 25[Formula: see text] respectively, in the pseudorapidity range [Formula: see text], [Formula: see text] and with an angular separation [Formula: see text], is [Formula: see text][Formula: see text]. Differential cross sections are measured as a function of the diphoton invariant mass, the diphoton transverse momentum, the azimuthal angle difference between the two photons, and the cosine of the polar angle in the Collins-Soper reference frame of the diphoton system. The results are compared to theoretical predictions at leading, next-to-leading, and next-to-next-to-leading order in quantum chromodynamics.
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35
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Observation of the diphoton decay of the Higgs boson and measurement of its properties. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2014; 74:3076. [PMID: 25814871 PMCID: PMC4370889 DOI: 10.1140/epjc/s10052-014-3076-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 09/12/2014] [Indexed: 05/30/2023]
Abstract
Observation of the diphoton decay mode of the recently discovered Higgs boson and measurement of some of its properties are reported. The analysis uses the entire dataset collected by the CMS experiment in proton-proton collisions during the 2011 and 2012 LHC running periods. The data samples correspond to integrated luminosities of 5.1[Formula: see text]at [Formula: see text] and 19.7[Formula: see text]at 8[Formula: see text] . A clear signal is observed in the diphoton channel at a mass close to 125[Formula: see text] with a local significance of [Formula: see text], where a significance of [Formula: see text] is expected for the standard model Higgs boson. The mass is measured to be [Formula: see text] , and the best-fit signal strength relative to the standard model prediction is [Formula: see text][Formula: see text][Formula: see text]. Additional measurements include the signal strength modifiers associated with different production mechanisms, and hypothesis tests between spin-0 and spin-2 models.
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36
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Searches for electroweak production of charginos, neutralinos, and sleptons decaying to leptons and W, Z, and Higgs bosons in pp collisions at 8 TeV. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2014; 74:3036. [PMID: 25814912 PMCID: PMC4370929 DOI: 10.1140/epjc/s10052-014-3036-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 08/16/2014] [Indexed: 05/23/2023]
Abstract
Searches for the direct electroweak production of supersymmetric charginos, neutralinos, and sleptons in a variety of signatures with leptons and [Formula: see text], [Formula: see text], and Higgs bosons are presented. Results are based on a sample of proton-proton collision data collected at center-of-mass energy [Formula: see text] with the CMS detector in 2012, corresponding to an integrated luminosity of 19.5 [Formula: see text]. The observed event rates are in agreement with expectations from the standard model. These results probe charginos and neutralinos with masses up to 720 [Formula: see text], and sleptons up to 260 [Formula: see text], depending on the model details.
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37
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Evidence of b-jet quenching in PbPb collisions at √(s(NN))=2.76 TeV. PHYSICAL REVIEW LETTERS 2014; 113:132301. [PMID: 25302881 DOI: 10.1103/physrevlett.113.132301] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Indexed: 06/04/2023]
Abstract
The production of jets associated to bottom quarks is measured for the first time in PbPb collisions at a center-of-mass energy of 2.76 TeV per nucleon pair. Jet spectra are reported in the transverse momentum (p(T)) range of 80-250 GeV/c, and within pseudorapidity |η|<2. The nuclear modification factor (R(AA)) calculated from these spectra shows a strong suppression in the b-jet yield in PbPb collisions relative to the yield observed in pp collisions at the same energy. The suppression persists to the largest values of p(T) studied, and is centrality dependent. The R(AA) is about 0.4 in the most central events, similar to previous observations for inclusive jets. This implies that jet quenching does not have a strong dependence on parton mass and flavor in the jet p(T) range studied.
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38
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Measurement of top quark-antiquark pair production in association with a W or Z boson in pp collisions at [Formula: see text][Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2014; 74:3060. [PMID: 25814914 PMCID: PMC4370853 DOI: 10.1140/epjc/s10052-014-3060-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 08/31/2014] [Indexed: 06/04/2023]
Abstract
A measurement of the cross section for the production of top quark-antiquark pairs ([Formula: see text]) in association with a vector boson V (W or Z) in proton-proton collisions at [Formula: see text][Formula: see text] is presented. The results are based on a dataset corresponding to an integrated luminosity of 19.5 fb[Formula: see text] recorded with the CMS detector at the LHC. The measurement is performed in three leptonic (e and [Formula: see text]) channels: a same-sign dilepton analysis targeting [Formula: see text] events, and trilepton and four-lepton analyses designed for [Formula: see text] events. In the same-sign dilepton channel, the [Formula: see text] cross section is measured as [Formula: see text], corresponding to a significance of 1.6 standard deviations over the background-only hypothesis. Combining the trilepton and four-lepton channels, a direct measurement of the [Formula: see text] cross section, [Formula: see text], is obtained with a significance of 3.1 standard deviations. The measured cross sections are compatible with standard model predictions within their experimental uncertainties. The inclusive [Formula: see text] process is observed with a significance of 3.7 standard deviations from the combination of all three leptonic channels.
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39
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Measurement of jet multiplicity distributions in [Formula: see text] production in pp collisions at [Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2014; 74:3014. [PMID: 25814909 PMCID: PMC4371091 DOI: 10.1140/epjc/s10052-014-3014-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Accepted: 07/30/2014] [Indexed: 06/02/2023]
Abstract
The normalised differential top quark-antiquark production cross section is measured as a function of the jet multiplicity in proton-proton collisions at a centre-of-mass energy of 7[Formula: see text] at the LHC with the CMS detector. The measurement is performed in both the dilepton and lepton+jets decay channels using data corresponding to an integrated luminosity of 5.0[Formula: see text]. Using a procedure to associate jets to decay products of the top quarks, the differential cross section of the [Formula: see text] production is determined as a function of the additional jet multiplicity in the lepton+jets channel. Furthermore, the fraction of events with no additional jets is measured in the dilepton channel, as a function of the threshold on the jet transverse momentum. The measurements are compared with predictions from perturbative quantum chromodynamics and no significant deviations are observed.
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40
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Search for invisible decays of Higgs bosons in the vector boson fusion and associated ZH production modes. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2014; 74:2980. [PMID: 25814906 PMCID: PMC4370888 DOI: 10.1140/epjc/s10052-014-2980-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 07/13/2014] [Indexed: 06/01/2023]
Abstract
A search for invisible decays of Higgs bosons is performed using the vector boson fusion and associated ZH production modes. In the ZH mode, the Z boson is required to decay to a pair of charged leptons or a [Formula: see text] quark pair. The searches use the 8 [Formula: see text] pp collision dataset collected by the CMS detector at the LHC, corresponding to an integrated luminosity of up to 19.7 [Formula: see text]. Certain channels include data from 7 [Formula: see text] collisions corresponding to an integrated luminosity of 4.9 [Formula: see text]. The searches are sensitive to non-standard-model invisible decays of the recently observed Higgs boson, as well as additional Higgs bosons with similar production modes and large invisible branching fractions. In all channels, the observed data are consistent with the expected standard model backgrounds. Limits are set on the production cross section times invisible branching fraction, as a function of the Higgs boson mass, for the vector boson fusion and ZH production modes. By combining all channels, and assuming standard model Higgs boson cross sections and acceptances, the observed (expected) upper limit on the invisible branching fraction at [Formula: see text] [Formula: see text] is found to be 0.58 (0.44) at 95 % confidence level. We interpret this limit in terms of a Higgs-portal model of dark matter interactions.
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41
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Measurement of WZ and ZZ production in pp collisions at [Formula: see text] in final states with b-tagged jets. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2014; 74:2973. [PMID: 25814904 PMCID: PMC4370898 DOI: 10.1140/epjc/s10052-014-2973-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 07/09/2014] [Indexed: 06/04/2023]
Abstract
Measurements are reported of the WZ and ZZ production cross sections in proton-proton collisions at [Formula: see text][Formula: see text] in final states where one Z boson decays to b-tagged jets. The other gauge boson, either W or Z, is detected through its leptonic decay (either [Formula: see text], [Formula: see text] or [Formula: see text], [Formula: see text], or [Formula: see text]). The results are based on data corresponding to an integrated luminosity of 18.9 fb[Formula: see text] collected with the CMS detector at the Large Hadron Collider. The measured cross sections, [Formula: see text] and [Formula: see text], are consistent with next-to-leading order quantum chromodynamics calculations.
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42
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Observation of the associated production of a single top quark and a W boson in pp collisions at sqrt[s] = 8 TeV. PHYSICAL REVIEW LETTERS 2014; 112:231802. [PMID: 24972196 DOI: 10.1103/physrevlett.112.231802] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Indexed: 06/03/2023]
Abstract
The first observation of the associated production of a single top quark and a W boson is presented. The analysis is based on a data set corresponding to an integrated luminosity of 12.2 fb(-1) of proton-proton collisions at sqrt[s] = 8 TeV recorded by the CMS experiment at the LHC. Events with two leptons and a jet originating from a b quark are selected. A multivariate analysis based on kinematic and topological properties is used to separate the signal from the dominant tt background. An excess consistent with the signal hypothesis is observed, with a significance which corresponds to 6.1 standard deviations above a background-only hypothesis. The measured production cross section is 23.4 ± 5.4 pb, in agreement with the standard model prediction.
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43
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Probing color coherence effects in pp collisions at [Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2014; 74:2901. [PMID: 25814895 PMCID: PMC4370765 DOI: 10.1140/epjc/s10052-014-2901-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 05/14/2014] [Indexed: 05/31/2023]
Abstract
A study of color coherence effects in pp collisions at a center-of-mass energy of 7[Formula: see text] is presented. The data used in the analysis were collected in 2010 with the CMS detector at the LHC and correspond to an integrated luminosity of 36 pb[Formula: see text]. Events are selected that contain at least three jets and where the two jets with the largest transverse momentum exhibit a back-to-back topology. The measured angular correlation between the second- and third-leading jet is shown to be sensitive to color coherence effects, and is compared to the predictions of Monte Carlo models with various implementations of color coherence. None of the models describe the data satisfactorily.
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44
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Study of the production of charged pions, kaons, and protons in pPb collisions at [Formula: see text]5.02[Formula: see text]. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2014; 74:2847. [PMID: 25814892 PMCID: PMC4370925 DOI: 10.1140/epjc/s10052-014-2847-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 04/04/2014] [Indexed: 05/28/2023]
Abstract
Spectra of identified charged hadrons are measured in pPb collisions with the CMS detector at the LHC at [Formula: see text]. Charged pions, kaons, and protons in the transverse-momentum range [Formula: see text]-1.7[Formula: see text] and laboratory rapidity [Formula: see text] are identified via their energy loss in the silicon tracker. The average [Formula: see text] increases with particle mass and the charged multiplicity of the event. The increase of the average [Formula: see text] with charged multiplicity is greater for heavier hadrons. Comparisons to Monte Carlo event generators reveal that Epos Lhc, which incorporates additional hydrodynamic evolution of the created system, is able to reproduce most of the data features, unlike Hijing and Ampt. The [Formula: see text] spectra and integrated yields are also compared to those measured in pp and PbPb collisions at various energies. The average transverse momentum and particle ratio measurements indicate that particle production at LHC energies is strongly correlated with event particle multiplicity.
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Measurement of inclusive W and Z boson production cross sections in pp collisions at sqrt[s] = 8 TeV. PHYSICAL REVIEW LETTERS 2014; 112:191802. [PMID: 24877930 DOI: 10.1103/physrevlett.112.191802] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Indexed: 06/03/2023]
Abstract
A measurement of total and fiducial inclusive W and Z boson production cross sections in pp collisions at sqrt[s] = 8 TeV is presented. Electron and muon final states are analyzed in a data sample collected with the CMS detector corresponding to an integrated luminosity of 18.2 ± 0.5 pb(-1). The measured total inclusive cross sections times branching fractions are σ(pp → WX)×B(W → ℓν) = 12.21 ± 0.03(stat) ± 0.24(syst) ± 0.32(lum) nb and σ(pp → ZX) × B(Z → ℓ+ℓ-) = 1.15 ± 0.01(stat) ± 0.02(syst) ± 0.03(lum) nb for the dilepton mass in the range of 60-120 GeV. The measured values agree with next-to-next-to-leading-order QCD cross section calculations. Ratios of cross sections are reported with a precision of 2%. This is the first measurement of inclusive W and Z boson production in proton-proton collisions at sqrt[s] = 8 TeV.
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Measurement of theWγandZγinclusive cross sections inppcollisions ats=7 TeVand limits on anomalous triple gauge boson couplings. Int J Clin Exp Med 2014. [DOI: 10.1103/physrevd.89.092005] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Measurements of tt spin correlations and top-quark polarization using dilepton final states in pp collisions at sqrt[s]=7 TeV. PHYSICAL REVIEW LETTERS 2014; 112:182001. [PMID: 24856688 DOI: 10.1103/physrevlett.112.182001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Indexed: 06/03/2023]
Abstract
Spin correlations and polarization in the top quark-antiquark system are measured using dilepton final states produced in pp collisions at the LHC at sqrt[s]=7 TeV. The data correspond to an integrated luminosity of 5.0 fb(-1) collected with the CMS detector. The measurements are performed using events with two oppositely charged leptons (electrons or muons), a significant imbalance in transverse momentum, and two or more jets, where at least one of the jets is identified as originating from a b quark. The spin correlations and polarization are measured through asymmetries in angular distributions of the two selected leptons, unfolded to the parton level. All measurements are found to be in agreement with predictions of the standard model.
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Search for top-quark partners with charge 5/3 in the same-sign dilepton final state. PHYSICAL REVIEW LETTERS 2014; 112:171801. [PMID: 24836237 DOI: 10.1103/physrevlett.112.171801] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Indexed: 06/03/2023]
Abstract
A search for the production of heavy partners of the top quark with charge 5/3 is performed in events with a pair of same-sign leptons. The data sample corresponds to an integrated luminosity of 19.5 fb(-1) and was collected at sqrt[s] = 8 TeV by the CMS experiment. No significant excess is observed in the data above the expected background, and the existence of top-quark partners with masses below 800 GeV is excluded at a 95% confidence level, assuming they decay exclusively to tW. This is the first limit on these particles from the LHC, and it is significantly more restrictive than previous limits.
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Search for flavor-changing neutral currents in top-quark decays t → Zq in pp collisions at sqrt[s] = 8 TeV. PHYSICAL REVIEW LETTERS 2014; 112:171802. [PMID: 24836238 DOI: 10.1103/physrevlett.112.171802] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Indexed: 06/03/2023]
Abstract
A search for flavor-changing neutral currents in top-quark decays t → Zq is performed in events produced from the decay chain tt → Zq+Wb, where both vector bosons decay leptonically, producing a final state with three leptons (electrons or muons). A data set collected with the CMS detector at the LHC is used, corresponding to an integrated luminosity of 19.7 fb(-1) of proton-proton collisions at a center-of-mass energy of 8 TeV. No excess is seen in the observed number of events relative to the standard model prediction; thus, no evidence for flavor-changing neutral currents in top-quark decays is found. A combination with a previous search at 7 TeV excludes a t → Zq branching fraction greater than 0.05% at the 95% confidence level.
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