7,135 research outputs found

    A Measurement of the Ratio of the W + 1 Jet to Z + 1 Jet Cross Sections with ATLAS

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    The measurement of hadronic activity recoiling against W and Z vector bosons provides an important test of perturbative QCD, as well as a method of searching for new physics in a model independent fashion. We present a study of the cross-section ratio for the production of W and Z gauge bosons in association with exactly one jet Rjet = {\sigma}(W + 1jet)/{\sigma}(Z + 1jet), in pp collisions at \surds = 7 TeV. The study is performed in the electron and muon channels with data collected with the ATLAS detector at the LHC. The ratio Rjet is studied as a function of the cumulative transverse momentum distribution of the jet. This result can be compared to NLO pQCD calculations and the prediction from LO matrix element + parton shower generators.Comment: 8 pages, 4 figures, conference proceedings for DPF 201

    A semiclassical model of light mesons

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    The dominantly orbital state description is applied to the study of light mesons. The effective Hamiltonian is characterized by a relativistic kinematics supplemented by the usual funnel potential with a mixed scalar and vector confinement. The influence of two different finite quark masses and potential parameters on Regge and vibrational trajectories is discussed.Comment: 1 figur

    Electromagnetic splitting for mesons and baryons using dressed constituent quarks

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    Electromagnetic splittings for mesons and baryons are calculated in a formalism where the constituent quarks are considered as dressed quasiparticles. The electromagnetic interaction, which contains coulomb, contact, and hyperfine terms, is folded with the quark electrical density. Two different types of strong potentials are considered. Numerical treatment is done very carefully and several approximations are discussed in detail. Our model contains only one free parameter and the agreement with experimental data is reasonable although it seems very difficult to obtain a perfect description in any case.Comment: 14 pages, Revised published versio

    Auxiliary field method and analytical solutions of the Schr\"{o}dinger equation with exponential potentials

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    The auxiliary field method is a new and efficient way to compute approximate analytical eigenenergies and eigenvectors of the Schr\"{o}dinger equation. This method has already been successfully applied to the case of central potentials of power-law and logarithmic forms. In the present work, we show that the Schr\"{o}dinger equation with exponential potentials of the form −αrλexp⁥(−ÎČr)-\alpha r^\lambda \exp(-\beta r) can also be analytically solved by using the auxiliary field method. Formulae giving the critical heights and the energy levels of these potentials are presented. Special attention is drawn on the Yukawa potential and the pure exponential one

    Tevatron Searches for New Physics with Photons and Jets

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    The D and CDF experiments have each collected more than 8 fb..1 in Run II of Fermilab\u27s Tevatron, and have many recent search results which use up to 5.2 fb..1. Here I summarize the results of a variety of searches for physics beyond the Standard Model with an emphasis on searches for very exotic phenomena. I will present the status of model-inspired searches for several signatures of supersymmetry, as well as several other searches for several \hidden- valley inspired models, all of which contain photons and jets in the nal state

    Sufficient conditions for the existence of bound states in a central potential

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    We show how a large class of sufficient conditions for the existence of bound states, in non-positive central potentials, can be constructed. These sufficient conditions yield upper limits on the critical value, gc(ℓ)g_{\rm{c}}^{(\ell)}, of the coupling constant (strength), gg, of the potential, V(r)=−gv(r)V(r)=-g v(r), for which a first ℓ\ell-wave bound state appears. These upper limits are significantly more stringent than hitherto known results.Comment: 7 page

    Universality of Regge and vibrational trajectories in a semiclassical model

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    The orbital and radial excitations of light-light mesons are studied in the framework of the dominantly orbital state description. The equation of motion is characterized by a relativistic kinematics supplemented by the usual funnel potential with a mixed scalar and vector confinement. The influence of finite quark masses and potential parameters on Regge and vibrational trajectories is discussed. The case of heavy-light mesons is also presented.Comment: 12 page

    Moving boundary approximation for curved streamer ionization fronts: Solvability analysis

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    The minimal density model for negative streamer ionization fronts is investigated. An earlier moving boundary approximation for this model consisted of a "kinetic undercooling" type boundary condition in a Laplacian growth problem of Hele-Shaw type. Here we derive a curvature correction to the moving boundary approximation that resembles surface tension. The calculation is based on solvability analysis with unconventional features, namely, there are three relevant zero modes of the adjoint operator, one of them diverging; furthermore, the inner/outer matching ahead of the front has to be performed on a line rather than on an extended region; and the whole calculation can be performed analytically. The analysis reveals a relation between the fields ahead and behind a slowly evolving curved front, the curvature and the generated conductivity. This relation forces us to give up the ideal conductivity approximation, and we suggest to replace it by a constant conductivity approximation. This implies that the electric potential in the streamer interior is no longer constant but solves a Laplace equation; this leads to a Muskat-type problem.Comment: 22 pages, 6 figure

    A mass formula for light mesons from a potential model

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    The quark dynamics inside light mesons, except pseudoscalar ones, can be quite well described by a spinless Salpeter equation supplemented by a Cornell interaction (possibly partly vector, partly scalar). A mass formula for these mesons can then be obtained by computing analytical approximations of the eigenvalues of the equation. We show that such a formula can be derived by combining the results of two methods: the dominantly orbital state description and the Bohr-Sommerfeld quantization approach. The predictions of the mass formula are compared with accurate solutions of the spinless Salpeter equation computed with a Lagrange-mesh calculation method.Comment: 5 figure