2,561 research outputs found
The GoSam package: an overview
The public code GOSAM for the computation of the one loop virtual corrections
to scattering amplitudes in the Standard Model and beyond is presented.
Particular emphasis is devoted to the interface with other public tools via the
Binoth Les Houches Accord. We show with examples that doing LHC phenomenology
including automatically Next to Leading Order QCD corrections is now handy.Comment: 8 pages, 4 figures, presented at the 11th DESY workshop "Loops and
Legs in Quantum Field Theory", April 2012, Wernigerode, German
Baryogenesis via leptogenesis in SO(10) models
We discuss the baryogenesis via leptogenesis mechanism within the
supersymmetric and nonsupersymmetric SO(10) models. We find that the
nonsupersymmetric model, endowed with an intermediate scale, is generally
favoured, unless some fine tuning occurs in the supersymmetric case.Comment: 9 pages, RevTex, with 1 figur
QCD corrections to J/psi and Upsilon production at hadron colliders
We calculate the cross section for hadroproduction of a pair of heavy quarks
in a 3S1 color-singlet state at next-to-leading order in QCD. This corresponds
to the leading contribution in the NRQCD expansion for J/psi and Upsilon
production. The higher-order corrections have a large impact on the p_T
distributions, enhancing the production at high p_T both at the Tevatron and at
the LHC. The total decay rate of a 3S1 into hadrons at NLO is also computed,
confirming for the first time the result obtained by Mackenzie and Lepage in
1981.Comment: 5 pages, 5 figure
Heavy quark radiation in NLO+PS POWHEG generators
In this paper we deal with radiation from heavy quarks in the context of
next-to-leading order calculations matched to parton shower generators. A new
algorithm for radiation from massive quarks is presented that has considerable
advantages over the one previously employed. We implement the algorithm in the
framework of the , and compare it with the previous one in
the case of the generator for bottom production in hadronic
collisions, and in the case of the generator for top production
and decay.Comment: 14 pages, 13 figures, LaTe
Neutrino masses and mixings in SO(10)
Assuming a Zee-like matrix for the right-handed neutrino Majorana masses in
the see-saw mechanism, one gets maximal mixing for vacuum solar oscillations, a
very small value for and an approximate degeneracy for the two lower
neutrino masses. The scale of right-handed neutrino Majorana masses is in good
agreement with the value expected in a SO(10) model with Pati-Salam SU(4)\ts
SU(2)\ts SU(2) intermediate symmetry.Comment: 11 pages, no figures. References adde
Fully exclusive heavy quark-antiquark pair production from a colourless initial state at NNLO in QCD
We present a local subtraction scheme for computing next-to-next-to-leading order QCD corrections to the production of a massive quark-antiquark pair from a colourless initial state. The subtraction terms are built following the CoLoRFulNNLO method and refined in such a way that their integration gives rise to compact, fully analytic expressions. All ingredients necessary for a numerical implementation of our subtraction scheme are provided in detail. As an example, we calculate the fully differential decay rate of the Standard Model Higgs boson to massive bottom quarks at next-to-next-to-leading order accuracy in perturbative QCD
Low Q 2 boundary conditions for DGLAP equations dictated by quantum statistical mechanics
We discuss the role of quantum statistical mechanics in the description of the parton distribution functions in the proton. It provides the low Q 2 boundary conditions for DGLAP equations in terms of FermiâDirac and BoseâEinstein functions of the fractional momentum variable x. The successful comparison with experimental data on both the unpolarised and polarised deep inelastic structure functions is reviewed. We argue that the statistical approach for the nucleon parton distributions functions has the nice feature that the free model parameters are fixed from data with high statistics and small systematic uncertainties, providing a strong constraint on the information not supplied by the experiments
Associated WH production at hadron colliders: a fully exclusive QCD calculation at NNLO
We consider QCD radiative corrections to Standard Model Higgs boson
production in association with a W boson in hadron collisions. We present a
fully exclusive calculation up to next-to-next-to-leading order (NNLO) in QCD
perturbation theory. To perform this NNLO computation, we use a recently
proposed version of the subtraction formalism. Our calculation includes
finite-width effects, the leptonic decay of the W boson with its spin
correlations, and the decay of the Higgs boson into a bbbar pair. We present
selected numerical results at the Tevatron and the LHC.Comment: 7 pages, 2 figure
The qT subtraction method: electroweak corrections and power suppressed contributions
Building upon the formulation of transverse-momentum resummation for heavy-quark hadroproduction, we present the first application of the qT subtraction formalism to the computation of electroweak corrections to massive lepton pairs through the DrellâYan mechanism. We then study the power suppressed contributions to the qT subtraction formula in the parameter rcut, defined as the minimum transverse momentum of the lepton pair normalised to its invariant mass. We analytically compute the leading power correction from initial and final-state radiation to the inclusive cross section. In the case of initial-state radiation the power correction is quadratic in rcut and our analytic result is consistent with results previously obtained in the literature. Final-state radiation produces linear contributions in rcut that may challenge the efficiency of the qT subtraction procedure. We explicitly compute the linear power correction in the case of the inclusive cross section and we discuss the extension of our calculation to differential distributions
NLO QCD corrections to the production of Higgs plus two jets at the LHC
We present the calculation of the NLO QCD corrections to the associated
production of a Higgs boson and two jets, in the infinite top-mass limit. We
discuss the technical details of the computation and we show the numerical
impact of the radiative corrections on several observables at the LHC. The
results are obtained by using a fully automated framework for fixed order NLO
QCD calculations based on the interplay of the packages GoSam and Sherpa. The
evaluation of the virtual corrections constitutes an application of the
d-dimensional integrand-level reduction to theories with higher dimensional
operators. We also present first results for the one-loop matrix elements of
the partonic processes with a quark-pair in the final state, which enter the
hadronic production of a Higgs boson together with three jets in the infinite
top-mass approximation.Comment: 9 pages, 7 figures, references added, published in Phys.Lett.
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