211 research outputs found
Fit to the Bjorken, Ellis-Jaffe and Gross-Llewellyn-Smith sum rules in a renormalon based approach
We study the large order behaviour in perturbation theory of the Bjorken,
Ellis-Jaffe and Gross-Llewellyn-Smith sum rules. In particular, we consider
their first infrared renormalons, for which we obtain their analytic structure
with logarithmic accuracy and also an approximate determination of their
normalization constant. Estimates of higher order terms of the perturbative
series are given. The Renormalon subtracted scheme is worked out for these
observables and compared with experimental data. Overall, good agreement with
experiment is found. This allows us to obtain {\hat a}_0 and some higher-twist
non-perturbative constants from experiment: {\hat a}_0=0.141\pm 0.089;
f_{3,RS}(1 GeV)=-0.124^{+0.137}_{-0.142} GeV^2.Comment: 23 pages, 18 figures, one reference added, journal versio
Di-boson Production beyond NLO QCD and Anomalous Couplings
In these proceedings, we review results for several di-boson production
processes beyond NLO QCD at high transverse momenta using the VBFNLO
Monte-Carlo program together with the LOOPSIM method. Additionally, we show for
the WZ production process how higher order QCD corrections can resemble
anomalous coupling effects.Comment: Conference Proceedings:C15-05-25.
Z\gamma\gamma production with leptonic decays and triple photon production at NLO QCD
We present a calculation of the O(alpha_s) QCD corrections to the production
of a Z boson in association with two photons and to triple photon production at
hadron colliders. All final-state photons are taken as real. For the Z boson,
we consider the decays both into charged leptons and into neutrinos including
all off-shell effects. Numerical results are obtained via a Monte Carlo program
based on the structure of the VBFNLO program package. This allows us to
implement general cuts and distributions of the final-state particles. We find
that the NLO QCD corrections are sizable and significantly exceed the
expectations from a scale variation of the leading-order result. In addition,
differential distributions of important observables change considerably. The
prediction of two-photon-associated Z production with Z decays into neutrinos
from the charged-lepton rate works well, once we use an additional cut on the
invariant mass of the charged-lepton pair.Comment: 14 pages, 10 figures, 2 table
Gluon Fusion induced Zg and Zgg Productions in the Standard Model at the LHC
We report calculations of the gluon induced Zg and Zgg productions in the
Standard Model at the LHC operating at both 7 TeV and 14 TeV collision energy.
We present total cross sections and differential distributions of the processes
and compare them with the leading and next-to-leading order QCD pp -> Z+1 jet,
Z+2 jets results. Our results show that the gluon induced Zg and Zgg
productions contribute to pp -> Z+1 jet, Z+2 jets at 1% level.Comment: 8 pages, 5 figure
NLO QCD corrections to W+W- gamma and Z Z gamma production with leptonic decays
The computation of the NLO QCD corrections to the cross sections for W+W-
gamma and ZZgamma production in hadronic collisions is presented. We consider
the case of a real photon in the final state, but include full leptonic decays
of the W and Z bosons. Numerical results for the LHC and the Tevatron are
obtained through a fully flexible parton level Monte Carlo based on the
structure of the VBFNLO program, allowing an easy implementation of arbitrary
cuts and distributions. We show the dependence on scale variations of the
integrated cross sections and provide evidence that NLO QCD corrections
strongly modify the LO predictions for observables at the LHC both in magnitude
and in shape
W\gamma \gamma production with leptonic decays at NLO QCD
The computation of the NLO-QCD corrections to the cross sections for W \gamma
\gamma production in hadronic collisions is presented. We consider the case of
real photons in the final state, but include full leptonic decays of the W.
Numerical results for the LHC and the Tevatron are obtained through a parton
level Monte Carlo based on the structure of the VBFNLO program, allowing an
easy implementation of general cuts and distributions. We show the dependence
on scale variations of the integrated cross sections and provide evidence of
the fact that NLO QCD corrections strongly modify the LO predictions for
observables at the LHC both in magnitude and in shape.Comment: 18 pages, 13 figure
Next-to-leading order QCD corrections to Wy production in association with two jets
We present the first calculation of next-to-leading order QCD corrections to
QCD-induced ZZ production in association with two jets at hadron colliders.
Both Z bosons decay leptonically with all off-shell effects, virtual photon
contributions and spin-correlation effects fully taken into account. This
process is an important background to weak boson scattering, to the measurement
of quartic gauge couplings and to searches for signals of new physics beyond
the Standard Model. As expected, the next-to-leading order corrections reduce
significantly the scale uncertainty and show a non-trivial phase space
dependence in kinematic distributions. Our code will be publicly available as
part of the parton level Monte Carlo program VBFNLO.Comment: 12 pages, 4 figures, 2 tables. arXiv admin note: text overlap with
arXiv:1402.050
NLO QCD corrections to processes with multiple electroweak bosons
The VBFNLO program package is a collection of Monte Carlo programs for the
calculation of NLO QCD corrections to vector boson fusion cross sections,
double and triple vector boson production, or the production of two electroweak
bosons in association with an additional jet. An overview is given of the
processes and features implemented in VBFNLO. WWgamma and Wgamma jet production
are discussed as examples.Comment: 6 pages, 3 figures; talk given at RADCOR 2009 - 9th International
Symposium on Radiative Corrections (Applications of Quantum Field Theory to
Phenomenology), October 25 - 30 2009, Ascona, Switzerlan
Gluon fusion into Higgs pairs at NLO QCD and the top mass scheme
We present the calculation of the full next-to-leading order (NLO) QCD corrections to Higgs boson pair production via gluon fusion at the LHC, including the exact top-mass dependence in the two-loop virtual and one-loop real corrections. This is the first independent cross-check of the NLO QCD corrections presented in the literature before. Our calculation relies on numerical integrations of Feynman integrals, stabilised with integration-by-parts and a Richardson extrapolation to the narrow width approximation. We present results for the total cross section as well as for the invariant Higgs-pair-mass distribution at the LHC, including for the first time a study of the uncertainty due to the scheme and scale choice for the top mass in the loops
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