6,782 research outputs found

    Q_T resummation in Higgs boson production at the LHC

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    When considering the transverse momentum distribution (q_T) of the Higgs boson production it is necessary to separate the small q_T region (q_T << M_H) from the medium and large (q_T > M_H) one, the former being treated by means of resummation techniques of logaritmhically-enhanced contributions and the latter by fixed-order perturbation theory. Then these two approaches have to be consistently matched to avoid double-counting in the intermediate q_T region. Here soft gluon resummation is implemented up to NNLL order and the matching to the corresponding NLO perturbative result is performed. Numerical results are shown for the LHC. The main features of the differential distribution turn out to be quite stable with respect to perturbative uncertainties.Comment: 5 pages, 2 figures,. Talk given in italian at "Incontri sulla Fisica delle Alte Energie", Lecce, Italy, 23-26 April 200

    Slepton production in polarized hadron collisions

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    We calculate cross sections and asymmetries for slepton pair production through neutral and charged electroweak currents in polarized hadron collisions for general slepton masses and including mixing of the left- and right-handed interaction eigenstates relevant for third generation sleptons. Our analytical results confirm and extend a previous calculation. Numerically, we show that measurements of the longitudinal single-spin asymmetry at the existing polarized pp collider RHIC and at possible polarization upgrades of the Tevatron or the LHC would allow for a determination of the tau slepton mixing angle and/or the associated supersymmetry breaking parameters Lambda for gauge mediation and A0 for minimal supergravity. Furthermore, the Standard Model background from tau pair production can be clearly distinguished due to the opposite sign of the associated asymmetry.Comment: 16 pages, 4 figures; Tevatron/LHC polarization and tau identification discussed, typos correcte

    Next-to-leading order QCD corrections to W+Z and W-Z production via vector-boson fusion

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    We present the calculation of the next-to-leading order QCD corrections to electroweak p p -> e+ nu_e mu+ mu- jj and p p -> e- nubar_e mu+ mu- jj production at the CERN LHC in the form of a fully flexible parton-level Monte Carlo program. The QCD corrections to the total cross sections are modest, changing the leading-order results by less than 10%. At the Born level, the shape of kinematic distributions can depend significantly on the choice of factorization scale. This theoretical uncertainty is strongly reduced by the inclusion of the next-to-leading order QCD corrections.Comment: 15 pages, 6 figures; new figure and comments added; version published by PR

    Squark and Gaugino Hadroproduction and Decays in Non-Minimal Flavour Violating Supersymmetry

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    We present an extensive analysis of squark and gaugino hadroproduction and decays in non-minimal flavour violating supersymmetry. We employ the so-called super-CKM basis to define the possible misalignment of quark and squark rotations, and we use generalized (possibly complex) charges to define the mutual couplings of (s)quarks and gauge bosons/gauginos. The cross sections for all squark-(anti-)squark/gaugino pair and squark-gaugino associated production processes as well as their decay widths are then given in compact analytic form. For four different constrained supersymmetry breaking models with non-minimal flavour violation in the second/third generation squark sector only, we establish the parameter space regions allowed/favoured by low-energy, electroweak precision, and cosmological constraints and display the chirality and flavour decomposition of all up- and down-type squark mass eigenstates. Finally, we compute numerically the dependence of a representative sample of production cross sections at the LHC on the off-diagonal mass matrix elements in the experimentally allowed/favoured ranges.Comment: 35 pages, 29 (partly colour) figures. Some typos corrected, wording of several paragraphs improved, version accepted by Nucl. Phys.

    QCD corrections to Higgs physics at the LHC

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    We summarize the status of QCD corrections for SM Higgs boson production at hadron colliders and briefly sketch the main search strategies at the LHC

    Transverse-Momentum Resummation for Slepton-Pair Production at the LHC

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    We perform a first precision calculation of the transverse-momentum (q_T) distribution of slepton pair and slepton-sneutrino associated production at the CERN Large Hadron Collider (LHC). We implement soft-gluon resummation at the next-to-leading logarithmic (NLL) level and consistently match the obtained result to the pure fixed-order perturbative result at leading order (LO) in the QCD coupling constant, i.e. O(alpha_s). We give numerical predictions for stau_1 stau_1^* and stau_1 sneutrino_tau^* + stau_1^* sneutrino_tau production, also implementing recent parameterizations of non-perturbative effects. The results show a relevant contribution of resummation both in the small and intermediate q_T-regions and little dependence on unphysical scales and non-perturbative contributions.Comment: 4 pages, 2 figure

    Transverse-momentum resummation and the spectrum of the Higgs boson at the LHC

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    We consider the transverse-momentum (q_T) distribution of generic high-mass systems (lepton pairs, vector bosons, Higgs particles, ....) produced in hadron collisions. At small q_T, we concentrate on the all-order resummation of the logarithmically-enhanced contributions in QCD perturbation theory. We elaborate on the bb-space resummation formalism and introduce some novel features: the large logarithmic contributions are systematically exponentiated in a process-independent form and, after integration over q_T, they are constrained by perturbative unitarity to give a vanishing contribution to the total cross section. At intermediate and large q_T, resummation is consistently combined with fixed-order perturbative results, to obtain predictions with uniform theoretical accuracy over the entire range of transverse momenta. The formalism is applied to Standard Model Higgs boson production at LHC energies. We combine the most advanced perturbative information available at present for this process: resummation up to next-to-next-to-leading logarithmic accuracy and fixed-order perturbation theory up to next-to-leading order. The results show a high stability with respect to perturbative QCD uncertainties.Comment: 48 pages, 13 postscript figure

    Threshold Effects in Slepton-Pair Production at the LHC

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    We present a study of threshold resummation effects for slepton pair production at the Large Hadron Collider (LHC). After confirming the known NLO QCD corrections and generalizing the NLO SUSY-QCD corrections to the case of mixing squarks in the virtual loop contributions, we employ the Mellin N-space resummation formalism to compute logarithmically enhanced soft-gluon terms to all perturbative orders.Comment: 3 pages, 1 figure, presented at HEP 2007 (Manchester, July 2007
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