24 research outputs found
QCD Corrections to Jet Correlations in Weak Boson Fusion
Higgs boson production via weak boson fusion is sensitive to the tensor
structure of the HVV (V=W,Z) couplings, which distinguishes loop induced
vertices from SM expectations. At the CERN Large Hadron Collider this
information shows up most clearly in the azimuthal angle correlations of the
two forward and backward quark jets which are typical for weak boson fusion. We
calculate the next-to-leading order QCD corrections to this process, in the
presence of anomalous HVV couplings. Gluon emission does not significantly
change the azimuthal jet correlations.Comment: 11 pages, 4 figure
A Forward Branching Phase Space Generator for Hadron colliders
In this paper we develop a projective phase space generator appropriate for
hadron collider geometry. The generator integrates over bremsstrahlung events
which project back to a single, fixed Born event. The projection is dictated by
the experimental jet algorithm allowing for the forward branching phase space
generator to integrate out the jet masses and initial state radiation. When
integrating over the virtual and bremsstrahlung amplitudes this results in a
single K-factor, assigning an event probability to each Born event. This
K-factor is calculable as a perturbative expansion in the strong coupling
constant. One can build observables from the Born kinematics, giving identical
results to tradi- tional observables as long as the observable does not depend
on the infrared sensitive jet mass or initial state radiation.Comment: 16 pages, 10 figure
Tau-Sneutrino NLSP and Multilepton Signatures at the LHC
In models with gravitino as the lightest supersymmetric particle(LSP), the
next to lightest supersymmetric particle (NLSP) can have a long lifetime and
appear stable in collider experiments. We study the leptonic signatures of such
a scenario with tau-sneutrino as the NLSP, which is realized in the
non-universal Higgs masses scenario. We focus on an interesting trilepton
signature with two like-sign taus and an electron or a muon of opposite sign.
The neutralinos and charginos are quite heavy in the model considered, and the
trilepton signal comes mostly from the slepton-sneutrino production. We
identify the relevant backgrounds, taking into account tau decays, and devise a
set of cuts to optimize this trilepton signal. We simulate signal and
backgrounds at the LHC with 14 TeV center-of-mass energy. Although the sleptons
in this model are relatively light, O(100 GeV), discovery is more demanding
compared to typical neutralino LSP scenarios. The trilepton signal requires
large amount of accumulated data, at least ~80 fb^-1, at the CM energy of 14
TeV.Comment: 25 pages, 6 figures, minor changes to match the version published in
Phys.Rev.
Higgs boson production in association with a photon via weak boson fusion
We present next-to-leading order QCD corrections to Higgs production in
association with a photon via weak boson fusion at a hadron collider. Utilizing
the fully flexible parton level Monte-Carlo program VBFNLO, we find small
overall corrections, while the shape of some distributions is sensitive to
radiative contributions in certain regions of phase-space. Residual scale
uncertainties at next-to-leading order are at the few-percent level. Being
perturbatively well under control and exhibiting kinematic features that allow
to distinguish it from potential backgrounds, this process can serve as a
valuable source of information on the Yukawa coupling.Comment: 8 pages. To appear in the proceedings of the "Photon 2011" conference
held in Spa, Belgium Added reference to arXiv:1105.0920 [hep-ph
Charged Higgs-boson production in association with an electron and a neutrino at electron-positron colliders
We present results of a calculation of the cross section for the production
of a charged Higgs boson in association with an electron and a neutrino at
electron-positron colliders (e+ e- -> H+ e- nu_e-bar, H- e+ nu_e). We study
predictions for the cross section in the Minimal Supersymmetric Standard Model
(MSSM) and the Two Higgs Doublet Model (THDM), highlighting possible
differences. The process is effectively loop-induced in both models. Hence, the
cross section is expected to be strongly model-dependent. Most notably, due to
the presence of superpartners, the MSSM amplitude contains Feynman graphs of
pentagon-type, which are not present in the THDM. This is the first complete
one-loop calculation of the cross section for this process in the THDM and the
MSSM. For both models, so far, only approximate results with limited ranges of
validity were available. Our main aim here is to clarify several open questions
in the existing literature on this process. Specifically, we will discuss the
validity of the Heavy Fermion loop approximation in both models, and of the
Fermion/Sfermion loop approximation in the MSSM.Comment: 21 pages, 8 figures, 1 tabl
Stress-testing the VBF approximation in multijet final states
We consider electro-weak Higgs plus three jets production at NLO QCD beyond
strict VBF acceptance cuts. We investigate, for the first time, how accurate
the VBF approximation is in these regions and within perturbative
uncertainties, by a detailed comparison of full and approximate calculations.
We find that a rapidity gap between the tagging jets guarantees a good
approximation, while an invariant mass cut alone is not sufficient, which needs
to be confronted with experimental choices. We also find that a significant
part of the QCD corrections can be attributed to Higgs-Strahlungs-type
topologies.Comment: 6 pages, 5 figures, add VBSCAN report numbe
Next-to-leading order QCD corrections to light Higgs Pair production via vector boson fusion
We present the NLO QCD corrections for light Higgs pair production via vector
boson fusion at the LHC within the CP conserving type II two higgs doublet
model in the form of a fully flexible parton--level Monte Carlo program. Scale
dependences on integrated cross sections and distributions are reduced with QCD
K-factors of order unity.Comment: 16 pages, 10 figures, 3 table
Stress testing the vector-boson-fusion approximation in multijet final states
We consider electroweak Higgs plus three jets production at NLO QCD beyond strict VBF acceptance cuts. We investigate, for the first time, how accurate the VBF approximation is in these regions and within perturbative uncertainties by a detailed comparison of full and approximate calculations. We find that a rapidity gap between the tagging jets guarantees a good approximation, while an invariant mass cut alone is not sufficient, which needs to be confronted with experimental choices. We also find that a significant part of the QCD corrections can be attributed to Higgs-Strahlungs-type topologies
Next-to-leading order QCD corrections to Higgs boson production in association with a photon via weak-boson fusion at the LHC
Higgs boson production in association with a hard central photon and two
forward tagging jets is expected to provide valuable information on Higgs boson
couplings in a range where it is difficult to disentangle weak-boson fusion
processes from large QCD backgrounds. We present next-to-leading order QCD
corrections to Higgs production in association with a photon via weak-boson
fusion at a hadron collider in the form of a flexible parton-level Monte Carlo
program. The QCD corrections to integrated cross sections are found to be small
for experimentally relevant selection cuts, while the shape of kinematic
distributions can be distorted by up to 20% in some regions of phase space.
Residual scale uncertainties at next-to-leading order are at the few-percent
level.Comment: 17 pages, 7 figures, 1 tabl