3,301 research outputs found

    Search for ADD Direct Graviton Emission in Photon plus Missing Transverse Energy Final State at CMS

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    The exclusive gamma and met signature is used as a probe for the discovery reach of ADD large extra dimensions at the CMS detector. Signal samples for various model parameters as well as possible backgrounds have beensimulated partially using the CMS fast detector simulation. The reconstruction performance and efficiency obtained with the fast simulation has been compared with the detailed full simulation. A normalisation method is proposed to measure the main background Z (rightarrow nunubar) +gamma with high precision using reference spectra from Z (rightarrow mu^+mu^-) + gamma and Z (rightarrow e^+ e^-) + gamma. The discovery reach at the LHC with CMS is presented and the potential to determine parameters of the underlying model is discussed

    Prospects for the Precision Measurement of the W Mass with the CMS Detector at the LHC

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    The precise measurement of the mass of the W boson constitutes an important consistency check of the Standard Model and is sensitive to supersymmetric corrections. Together with the top quark mass, the W mass discriminates between the Standard Model and supersymmetric extensions. In this note, methods are presented which employ the large number of Z bosons produced at the LHC to significantly reduce theoretical and experimental uncertainties on the W mass measurement. A precision of about 40 MeV (20 MeV) with the first 1 fb^-1 (10 fb^-1) of integrated luminosity during the low luminosity run of the LHC is expected

    Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

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    The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum
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