58 research outputs found

    Measurement of prompt D0^{0} and D\overline{D}0^{0} meson azimuthal anisotropy and search for strong electric fields in PbPb collisions at root SNN\sqrt{S_{NN}} = 5.02 TeV

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    The strong Coulomb field created in ultrarelativistic heavy ion collisions is expected to produce a rapiditydependent difference (Av2) in the second Fourier coefficient of the azimuthal distribution (elliptic flow, v2) between D0 (uc) and D0 (uc) mesons. Motivated by the search for evidence of this field, the CMS detector at the LHC is used to perform the first measurement of Av2. The rapidity-averaged value is found to be (Av2) = 0.001 ? 0.001 (stat)? 0.003 (syst) in PbPb collisions at ?sNN = 5.02 TeV. In addition, the influence of the collision geometry is explored by measuring the D0 and D0mesons v2 and triangular flow coefficient (v3) as functions of rapidity, transverse momentum (pT), and event centrality (a measure of the overlap of the two Pb nuclei). A clear centrality dependence of prompt D0 meson v2 values is observed, while the v3 is largely independent of centrality. These trends are consistent with expectations of flow driven by the initial-state geometry. ? 2021 The Author. Published by Elsevier B.V. This is an open access article under the CC BY licens

    Measurement of the CP-violating phase ϕs_{s} in the B0^{0}s_{s}→J/ψ φ(1020) →μ⁺μ⁻K⁺K⁻ channel in proton-proton collisions at √s = 13 TeV

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    Observation of electroweak production of Wγ with two jets in proton-proton collisions at √s = 13 TeV

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    A first observation is presented for the electroweak production of a W boson, a photon, and two jets in proton-proton collisions. The W boson decays are selected by requiring one identified electron or muon and an imbalance in transverse momentum. The two jets are required to have a high dijet mass and a large separation in pseudorapidity. The measurement is based on data collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb1^{-1}. The observed (expected) significance for this process is 4.9 (4.6) standard deviations. After combining with previously reported CMS results at 8 TeV, the observed (expected) significance is 5.3 (4.8) standard deviations. The cross section for the electroweak Wγjj_{γjj} production in a restricted fiducial region is measured as 20.4 +/- 4.5 fb and the total cross section for Wγ_{γ} production in association with 2 jets in the same fiducial region is 108 +/- 16 fb. All results are in good agreement with recent theoretical predictions. Constraints are placed on anomalous quartic gauge couplings in terms of dimension-8 effective field theory operators

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

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    Measurements of production cross sections of polarized same-sign W boson pairs in association with two jets in proton-proton collisions at s=13 TeV

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    The first measurements of production cross sections of polarized same-sign W±W±boson pairs in proton-proton collisions are reported. The measurements are based on a data sample collected with the CMS detector at the LHC at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 137fb−1. Events are selected by requiring exactly two same-sign leptons, electrons or muons, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass to enhance the contribution of same-sign W±W±scattering events. An observed (expected) 95% confidence level upper limit of 1.17 (0.88)fbis set on the production cross section for longitudinally polarized same-sign W±W±boson pairs. The electroweak production of same-sign W±W±boson pairs with at least one of the Wbosons longitudinally polarized is measured with an observed (expected) significance of 2.3 (3.1) standard deviations.SCOAP

    Broadband two-layer shorted patch antenna with low cross-polarisation

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    The design and experimental results of a new configuration two-layer shorted square microstrip antenna with low cross-polarisation are described. The antenna has a bandwidth of 11 centred around 1.975GHz with a gain of 8.6dB, and exhibits better than -13dB cross-polarisation levels in the H-plane. The computed and measured results of the co-planar configuration of the structure are compared with its new two-layer stacked configuration

    Stacked shorted microstrip antenna for low cross polarization and wide-band

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    A novel structure to improve the cross-polarization characteristics of the shorted square microstrip antenna is presented. The square-ring patch is used as a parasitic element in the stacked position to tune the input impedance, resonant frequency, cross polarization, and bandwidth of the shorted square microstrip antenna. As a result, 11% bandwidth and better than - 14.5 dB cross-polarization levels have been achieved. The theoretical results are compared with the experimental results. © 2001 John Wiley & Sons, Inc

    High pressure electrical measurements on Ge-Te-Se glasses

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    Electrical resistivity measurements have been carried out on bulk Ge-Te-Se glasses in a Bridgman anvil system. The resistivity of the Ge-Te-Se samples is found to decrease continuously with increasing pressure, with the metallization occurring around 8GPa. Ge20TexSe80-x glasses (10 ⤠x ⤠50) with the mean co-ordination number Zav = 2.4 exhibit a plateau in resistivity up to about 4 GPa pressure, followed by a continuous decrease to metallic values. On the other hand, Ge10TexSe90-x glasses (10 ⤠x ⤠40) having Zav = 2.2, exhibit a smaller plateau (only up to 1 GPa), followed by a decrease in resistivity with pressure. This subtle difference in the high pressure resistivity of Ge-Te-Se glasses with Zav < 2.4 and Zav ⥠2.4 can be associated with the changes in the local structure of the chalcogenide glasses with composition

    Thermal crystallization behaviour of Ge-Te-Se glasses

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    Ge10Te90-xSex (50 ⤠x ⤠70) and Ge20Te80-xSex (x = 30, 50) glasses have been prepared by melt-quenching. The thermal crystallization behaviour of these samples has been studied by Differential Scanning Calorimetry (DSC), in order to characterise these glasses for memory-threshold switching applications. It is found that Ge10Te90-xSex glasses have higher thermal stability and are more stable against devitrification. These samples may be suitable for threshold switching devices. Ge20Te80-xSex glasses, on the other hand, phase separate on heating and exhibit a double stage crystallization. Based on this, it can be expected that Ge20Te80-xSex samples will show memory behaviour. The activation energy for thermal crystallization of a representative Ge10Te40Se50 glass belonging to the Ge10Te90-xSex series has been found by the Kissinger's method to be 0.92 eV. The value of the activation energy obtained also indicates that Ge10Te90-xSex samples are less prone to devitrification and more suitable for threshold behaviour

    Pressure-induced metallization in AlAsTe glasses

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    Electrical resistivity measurements have been undertaken on bulk AlAsTe glasses at pressures up to 8 GPa and to 80 K in a Bridgman anvil setup. The samples have been found to show a continuous decrease in resistivity with increasing pressures. The activation energy of electrical conduction is also found to decrease monotonically, indicating a pressure-induced semiconductor-metal transformation in AlAsTe glasses. The metallization pressures of AlAsTe samples increase with increasing Al content. The high-pressure metallic phases of AlAsTe samples are found to be amorphous. The results show that the high-pressure behaviour of AlAsTe glasses are closer to that of AsTe glasses than to that of AlTe glasses. © 1995
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