301 research outputs found

    Opportunities with top quarks at future circular colliders

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    We describe various studies relevant for top physics at future circular collider projects currently under discussion. We show how highly-massive top-antitop systems produced in proton-proton collisions at a center-of-mass energy of 100 TeV could be observed and employed for constraining top dipole moments, investigate the reach of future proton-proton and electron-positron machines to top flavor-changing neutral interactions, and discuss top parton densities.Comment: 5 pages, 2 figures, 1 table; to appear in the proceedings of the "7th International Workshop on Top Quark Physics", 28 Sep - 3 Oct 2014, Cannes, Franc

    Transverse-momentum, threshold and joint resummations for slepton pair production at hadron colliders

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    We present precision calculations of the transverse-momentum spectrum and the invariant-mass distribution for slepton pair production at hadron colliders. We implement the transverse-momentum, threshold and joint resummation formalisms at the next-to-leading logarithmic accuracy and consistently match the obtained result with the pure perturbative result at the first order in the strong coupling constant, i.e. at order alpha_s. We give numerical predictions for selectron and stau pair production, and compare the various resummed cross sections with the perturbative result.Comment: Submitted for the SUSY07 proceedings, 4 pages, 4 eps figure

    Slepton pair production at hadron colliders

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    In R-parity conserving supersymmetric models, sleptons are produced in pairs at hadron colliders. We show that measurements of the longitudinal single-spin asymmetry at possible polarization upgrades of existing colliders allow for a direct extraction of the slepton mixing angle. A calculation of the transverse-momentum spectrum shows the importance of resummed contributions at next-to-leading logarithmic accuracy in the small and intermediate transverse-momentum regions and little dependence on unphysical scales and non-perturbative contributions.Comment: 4 pages, 3 figures, to appear in Proceedings of SUSY06, the 14th International Conference on Supersymmetry and the Unification of Fundamental Interactions, UC Irvine, California, 12-17 June 200

    MadAnalysis 5: status and new developments

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    MadAnalysis 5 is a new Python/C++ package facilitating phenomenological analyses that can be performed in the framework of Monte Carlo simulations of collisions to be produced in high-energy physics experiments. It allows, by means of a user-friendly interpreter, to perform professional physics analyses in a very simple way. Starting from event samples as generated by any Monte Carlo event generator, large classes of selections can be implemented through intuitive commands, many standard kinematical distributions can be automatically represented by histograms and all results are eventually gathered into detailed Html and latex reports. In this work, we briefly report on the latest developments of the code, focusing on the interface to the FastJet program dedicated to jet reconstruction.Comment: 8 pages, 1 figure, contribution to the proceedings of the 15th International Workshop of advanced computing and analysis techniques (ACAT 2013), 16-21 May 2013, China; version to appear in the proceeding

    QCD next-to-leading-order predictions matched to parton showers for vector-like quark models

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    Vector-like quarks are featured by a wealth of beyond the Standard Model theories and are consequently an important goal of many LHC searches for new physics. Those searches, as well as most related phenomenological studies, however rely on predictions evaluated at the leading-order accuracy in QCD and consider well-defined simplified benchmark scenarios. Adopting an effective bottom-up approach, we compute next-to-leading-order predictions for vector-like-quark pair-production and single production in association with jets, with a weak or with a Higgs boson in a general new physics setup. We additionally compute vector-like-quark contributions to the production of a pair of Standard Model bosons at the same level of accuracy. For all processes under consideration, we focus both on total cross sections and on differential distributions, most these calculations being performed for the first time in our field. As a result, our work paves the way to precise extraction of experimental limits on vector-like quarks thanks to an accurate control of the shapes of the relevant observables and emphasize the extra handles that could be provided by novel vector-like-quark probes never envisaged so farComment: 21 pages, 12 figures, 6 tables; model files available from http://feynrules.irmp.ucl.ac.be/wiki/NLOModels; version accepted by EPJ

    Cornering sgluons with four-top-quark events

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    The existence of colour-octet scalar states, often dubbed sgluons, is predicted in many extensions of the Standard Model of particle physics, such as supersymmetric realisations featuring Dirac gauginos. Such states have a large pair-production rate at hadron colliders and mainly decay into pairs of jets and top quarks. Consequently, they represent a primary target for experimental searches for new resonances in the multijet and multitop channels at the Large Hadron Collider. Adopting a phenomenologically-motivated simplified model, we reinterpret the results of a recent experimental search for the four-top-quark Standard Model signal, from which we constrain the sgluon mass to be larger than about 1.06 TeV. We additionally consider how modifications of the existing four-top-quark studies could enhance our ability to unravel the presence of scalar octets in data.Comment: 8 pages, 4 figures. References added, matches published versio