67 research outputs found

    Critical fluctuation conductivity in layered superconductors in strong electric field

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    The paraconductivity, originating from critical superconducting order-parameter fluctuations in the vicinity of the critical temperature in a layered superconductor is calculated in the frame of the self-consistent Hartree approximation, for an arbitrarily strong electric field and zero magnetic field. The paraconductivity diverges less steep towards the critical temperature in the Hartree approximation than in the Gaussian one and it shows a distinctly enhanced variation with the electric field. Our results indicate that high electric fields can be effectively used to suppress order-parameter fluctuations in high-temperature superconductors.Comment: 11 pages, 2 figures, to be published in Phys. Rev.

    Measurements of differential production cross sections for a Z boson in association with jets in pp collisions at root s=8 TeV

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    Search for the associated production of the Higgs boson with a top-quark pair

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    A search for the standard model Higgs boson produced in association with a top-quark pair t t ÂŻ H (ttÂŻH) is presented, using data samples corresponding to integrated luminosities of up to 5.1 fb −1 and 19.7 fb −1 collected in pp collisions at center-of-mass energies of 7 TeV and 8 TeV respectively. The search is based on the following signatures of the Higgs boson decay: H → hadrons, H → photons, and H → leptons. The results are characterized by an observed t t ÂŻ H ttÂŻH signal strength relative to the standard model cross section, μ = σ/σ SM ,under the assumption that the Higgs boson decays as expected in the standard model. The best fit value is μ = 2.8 ± 1.0 for a Higgs boson mass of 125.6 GeV

    Measurement of prompt Jψ\psi pair production in pp collisions at \sqrt s = 7 Tev

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    Production of prompt J/ ψ meson pairs in proton-proton collisions at s s√ = 7 TeV is measured with the CMS experiment at the LHC in a data sample corresponding to an integrated luminosity of about 4.7 fb −1 . The two J/ ψ mesons are fully reconstructed via their decays into μ + μ − pairs. This observation provides for the first time access to the high-transverse-momentum region of J/ ψ pair production where model predictions are not yet established. The total and differential cross sections are measured in a phase space defined by the individual J/ ψ transverse momentum ( p T J/ ψ ) and rapidity (| y J/ ψ |): | y J/ ψ | 6.5 GeV/ c ; 1.2 4.5 GeV/ c . The total cross section, assuming unpolarized prompt J/ ψ pair production is 1.49 ± 0.07 (stat) ±0.13 (syst) nb. Different assumptions about the J/ ψ polarization imply modifications to the cross section ranging from −31% to +27%

    Measurements of the t(t)Overbar charge asymmetry using the dilepton decay channel in pp collisions at root s=7 TeV

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    The ttÂŻ charge asymmetry in proton-proton collisions at s√ = 7 TeV is measured using the dilepton decay channel (ee, e μ , or μμ ). The data correspond to a total integrated luminosity of 5.0 fb −1 , collected by the CMS experiment at the LHC. The tt and lepton charge asymmetries, defined as the differences in absolute values of the rapidities between the reconstructed top quarks and antiquarks and of the pseudorapidities between the positive and negative leptons, respectively, are measured to be A C = −0 . 010 ± 0 . 017 (stat . ) ± 0 . 008 (syst . ) and AlepC = 0 . 009 ± 0 . 010 (stat . ) ± 0 . 006 (syst . ). The lepton charge asymmetry is also measured as a function of the invariant mass, rapidity, and transverse momentum of the ttÂŻ system. All measurements are consistent with the expectations of the standard model

    Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC

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    Readout technologies for directional WIMP Dark Matter detection

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    The measurement of the direction of WIMP-induced nuclear recoils is a compelling but technologically challenging strategy to provide an unambiguous signature of the detection of Galactic dark matter. Most directional detectors aim to reconstruct the dark-matter-induced nuclear recoil tracks, either in gas or solid targets. The main challenge with directional detection is the need for high spatial resolution over large volumes, which puts strong requirements on the readout technologies. In this paper we review the various detector readout technologies used by directional detectors. In particular, we summarize the challenges, advantages and drawbacks of each approach, and discuss future prospects for these technologies

    Charged-particle nuclear modification factors in PbPb and pPb collisions at √=sNN=5.02 TeV

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    The spectra of charged particles produced within the pseudorapidity window |η| < 1 at √ sNN = 5.02 TeV are measured using 404 ”b −1 of PbPb and 27.4 pb−1 of pp data collected by the CMS detector at the LHC in 2015. The spectra are presented over the transverse momentum ranges spanning 0.5 < pT < 400 GeV in pp and 0.7 < pT < 400 GeV in PbPb collisions. The corresponding nuclear modification factor, RAA, is measured in bins of collision centrality. The RAA in the 5% most central collisions shows a maximal suppression by a factor of 7–8 in the pT region of 6–9 GeV. This dip is followed by an increase, which continues up to the highest pT measured, and approaches unity in the vicinity of pT = 200 GeV. The RAA is compared to theoretical predictions and earlier experimental results at lower collision energies. The newly measured pp spectrum is combined with the pPb spectrum previously published by the CMS collaboration to construct the pPb nuclear modification factor, RpA, up to 120 GeV. For pT > 20 GeV, RpA exhibits weak momentum dependence and shows a moderate enhancement above unity

    A method to study the kinetics of oral mucosal drug absorption from solutions

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    Abstract— A method has been developed which allows the kinetics of oral mucosal drug absorption from solutions to be studied in a single 15–20 min test. This is an improvement over the traditional buccal absorption test which requires a separate experiment for each time point, thus taking days for each kinetic profile. It should also allow for disappearance of drug from the mouth and appearance in the plasma to be monitored simultaneously. The drug solution includes 8 ÎŒg mL phenol red as a marker for salivary secretion. Samples are withdrawn at suitable times with a positive displacement pipettor and analysed for drug and phenol red. Salivary volume time data are described by least squares polynomials. Kinetic parameters are estimated by non‐linear least squares regression. The method, which requires that phenol red is not lost during a test, provides an internal test for this. It also requires that phenol red and the drug do not interfere with each other's assay, that saliva does not affect the assays of these materials, and that phenol red does not interfere with the absorption of the drug. 1988 Royal Pharmaceutical Society of Great Britai

    Estimation of all parameters from nonisothermal kinetic data

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    A method is described which estimates (using least‐squares analysis) all parameters (kinetic parameters and also zero and infinite time assays) from nonisothermal kinetic data. This method overcomes the time delays required for infinite time assays and biased estimates caused by the use of those assay results. Flexible temperature and data collection programs can be used. The mathematical models account for thermal volume expansion and the appropriate model is selected by statistical tests (provided the reaction is studied over ∌90% decomposition). The models use a reparameterized Arrhenius equation in which the frequency factor is replaced by k, the rate constant at a specified temperature. This improves the numerical procedure and allows room temperature stability to be estimated directly. Copyrigh
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