86 research outputs found
Precise predictions for MSSM Higgs-boson production in bottom-quark fusion
The main production mechanism for supersymmetric Higgs particles at hadron
colliders crucially depends on the size of their Yukawa couplings to bottom
quarks. For sufficiently large tan(beta) the total cross section for some of
the neutral Higgs bosons in the MSSM is dominated by bottom-quark fusion. After
an introduction to bottom-associated Higgs production, we discuss the complete
O(alpha) electroweak and O(alpha_s) strong corrections for the bb-fusion
channel in the MSSM. Choosing proper renormalization and input-parameter
schemes, an improved Born approximation, constructed from previously known
results, can absorb the bulk of the corrections so that the remaining
non-universal corrections are typically of the order of a few per cent.
Numerical results are discussed for the SPS benchmark scenarios.Comment: Submitted for the SUSY07 proceedings, 4 pages, 2 figure
Resonance-improved parton-shower matching for the Drell-Yan process including electroweak corrections
We use the POWHEG method to perform parton-shower matching for Drell-Yan
production of W and Z bosons at the LHC at NLO QCD and NLO electroweak
accuracy. In particular, we investigate an improved treatment of the
vector-boson resonances within the POWHEG method. We employ an independent
implementation of the POWHEG method and compare to earlier results within the
POWHEGBOX. On the technical side, we provide the FKS formalism for
photon-radiation off fermions within mass regularization.Comment: 29 pages, 6 figures, extended discussions; version published in JHE
LEP Constraints on 5-Dimensional Extensions of the Standard Model
We study minimal 5-dimensional extensions of the Standard Model, in which all
or only some of the SU(2) and U(1) gauge fields and Higgs bosons
propagate in the fifth compact dimension. In all the 5-dimensional settings,
the fermions are assumed to be localized on a 3-brane. In addition, we present
the consistent procedure for quantizing 5-dimensional models in the generalized
gauge. Bounds on the compactification scale between 4 and 6 TeV,
depending on the model, are established by analyzing electroweak precision
measurements and LEP2 cross sections.Comment: 6 pages, talk given at the 10th international conference on
``Supersymmetry and Unification of Fundamental Interactions,'' Hamburg,
Germany, 17--23 June 200
Electroweak corrections to W + jet hadroproduction including leptonic W-boson decays
We present the first calculation of the next-to-leading-order electroweak
corrections to W-boson + jet hadroproduction including leptonic W-boson decays.
The W-boson resonance is treated consistently using the complex-mass scheme,
and all off-shell effects are taken into account. The corresponding
next-to-leading-order QCD corrections have also been recalculated. All the
results are implemented in a flexible Monte Carlo code. Numerical results for
cross sections and distributions of this Standard Model benchmark process are
presented for the Tevatron and the LHC.Comment: 32 pages, 12 figures, a few comments added, version published in JHE
Electroweak corrections to monojet production at the Tevatron and the LHC
Single-jet production with missing transverse momentum is one of the most
promising discovery channels for new physics at the LHC. In the Standard Model,
Z + jet production with a Z-boson decay into neutrinos leads to this monojet
signature. To improve the corresponding Standard Model predictions, we present
the calculation of the full next-to-leading-order (NLO) electroweak corrections
and a recalculation of the NLO QCD corrections to monojet production at the
Tevatron and the LHC. We discuss the phenomenological impact on the total cross
sections as well as on relevant differential distributions.Comment: 22 pages, 10 figures, 6 tables. Sections 2 and 3 shortened, comments
on experimental uncertainties added, some references added; version to appear
in EPJC. arXiv admin note: text overlap with arXiv:1103.091
Radiative distortion of kinematic edges in cascade decays
Kinematic edges of cascade decays of new particles produced in high-energy
collisions may provide important constraints on the involved particles' masses.
For the exemplary case of gluino decay into
a pair of quarks and a neutralino through a squark resonance, we study the
hadronic invariant mass distribution in the vicinity of the kinematic edge. We
perform a next-to-leading order calculation in the strong coupling
and the ratio of squark width and squark mass \Gamma_\tilde{q}/m_\tilde{q},
based on a systematic expansion in \Gamma_\tilde{q}/m_\tilde{q}. The
separation into hard, collinear and soft contributions elucidates the process
dependent and universal features of distributions in the edge region,
represented by on-shell decay matrix elements, universal jet functions and a
soft function that depends on the resonance propagator and soft Wilson lines.Comment: 15 pages, 5 figure
Electroweak precision for W+jet production
In this talk we discuss the next-to-leading-order electroweak (EW)
corrections to W-boson + jet hadroproduction [1] and compare the full result to
a simple approximation assuming factorization of EW and QCD corrections for the
charged-current Drell-Yan process. The W-boson resonance is treated
consistently using the complex-mass scheme, and all off-shell effects are taken
into account. The corresponding next-to-leading-order QCD corrections have also
been recalculated. All the results are implemented in a flexible Monte Carlo
code. Selected numerical results for this Standard Model benchmark process are
presented for the LHC. The comparison of our result to an approximation based
on the EW corrections to W-boson production without additional jets is a step
towards a better understanding of the interplay between QCD and EW effects for
W-boson production in general.Comment: 6+1 pages, contribution to the proceedings of the 9th International
Symposium on Radiative Corrections (RADCOR 2009), October 25-30 2009, Ascona,
Switzerlan
HAWK 2.0: A Monte Carlo program for Higgs production in vector-boson fusion and Higgs strahlung at hadron colliders
The Monte Carlo integrator HAWK provides precision predictions for Higgs
production at hadron colliders in vector-boson fusion and Higgs strahlung, i.e.
in production processes where the Higgs boson is Attached to WeaK bosons. The
fully differential predictions include the full QCD and electroweak
next-to-leading-order corrections. Results are computed as integrated cross
sections and as binned distributions for important hadron-collider observables.Comment: 33 pages, 1 figur
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