760 research outputs found

    Search For A Heavy Gauge Boson W' In The Final State With An Electron And Large Missing Transverse Energy In Pp Collisions At Sqrt(S) = 7 Tev

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    A search for a heavy gauge boson W has been conducted by the CMS experiment at the LHC in the decay channel with an electron and large transverse / energy imbalance, E T , using proton-proton collision data corresponding to an integrated luminosity of 36 pb[-]1 . No excess above standard model expectations / is seen in the transverse mass distribution of the electron-E T system. Assuming standard-model-like couplings and decay branching fractions, a W boson with a mass less than 1.32 TeV/c2 is excluded at the 95% confidence level

    Large Extra Dimensions

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    Abstract The possibility of extra dimensions has been considered for a long time. In the 1920's, Kaluza and Klein sought to unify electromagnetism with gravity by adding an extra dimension that was curled up on the order of the Planck length (10 -35 m.) Then, string theory sought to unify quantum mechanics and general relativity. Although it is a major contender for a quantum theory of gravity, it requires 6 or 7 additional spatial dimensions that are compactified. Extensions of string theory led to membranes (or branes) as objects in a higher dimensional space. It is possible that all of the particles and fields of the Standard Model are trapped on this brane, providing an explanation for why we have never observed more than our 3 spatial dimensions. On the other hand, gravity would be able to travel in (4 + n) dimensions, where n is the number of extra dimensions. Since we are constrained to the brane, extra dimensions need not be compactified, leading to theories with large extra dimensions. One of the first theories was developed by Arkani-Hamed, Dimopoulos, and Dvali. They proposed that for n = 2, the extra dimensions could be as large as a millimeter. In addition to this possibility, they found that their model could also describe the hierarchy between the Planck mass and the electroweak symmetry breaking scale in terms of the large size of the extra dimensions. Randall and Sundrum proposed a different brane world in which the hierarchy was due to an exponential warped factor caused by branes with tension in an Anti-de Sitter five-dimensional geometry. In their model, the extra dimension could even be of infinite size and still reproduce our fourdimensional gravity. Thus, it was found that large extra dimensions were not only allowed theoretically, but they provided an explanation for the hierarchy problem that has been a longstanding problem in particle physics

    Differential cross section measurements for the production of a W boson in association with jets in proton‚Äďproton collisions at ‚ąös = 7 TeV

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    Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript ‚ąí1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

    Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an