11,981 research outputs found
Triphoton production at hadron colliders
We present next-to-leading order predictions for the production of triphoton
final states at the LHC and the Tevatron. Our results include the effect of
photon fragmentation for the first time and we are able to quantify the impact
of different isolation prescriptions. We find that calculations accounting for
fragmentation effects at leading order, and those employing a smooth cone
isolation where no fragmentation contribution is required, are in reasonable
agreement with one another. However, larger differences in the predicted rates
arise when higher order corrections to the fragmentation functions are
included. In addition we present full analytic results for the
and jet one-loop amplitudes. These
amplitudes, which are particularly compact, may be useful to future
higher-order calculations. Our results are available in the Monte Carlo code
MCFM.Comment: 16 pages, 4 figure
production at NNLO including anomalous couplings
In this paper we present a next-to-next-to-leading order (NNLO) QCD
calculation of the processes and that we have implemented in MCFM. Our calculation includes
QCD corrections at NNLO both for the Standard Model (SM) and additionally in
the presence of and anomalous couplings. We compare
our implementation, obtained using the jettiness slicing approach, with a
previous SM calculation and find broad agreement. Focusing on the sensitivity
of our results to the slicing parameter, we show that using our setup we are
able to compute NNLO cross sections with numerical uncertainties of about
, which is small compared to residual scale uncertainties of a few
percent. We study potential improvements using two different jettiness
definitions and the inclusion of power corrections. At TeV we
present phenomenological results and consider as a background to
production. We find that, with typical cuts, the inclusion of
NNLO corrections represents a small effect and loosens the extraction of limits
on anomalous couplings by about .Comment: 30 pages, 14 figure
NLO predictions for a lepton, missing transverse momentum and dijets at the Tevatron
n this letter we investigate the various processes that can contribute to a
final state consisting of a lepton, missing transverse momentum and two jets at
Next to Leading Order (NLO) at the Tevatron. In particular we consider the
production of W/Z + 2 jets, diboson pairs, single top and the tt process with
both fully leptonic and semi-leptonic decays. We present distributions for the
invariant mass of the dijet system and normalisations of the various processes,
accurate to NLO.Comment: 4 pages, 5 figure
QCD corrections to the hadronic production of a heavy quark pair and a W-boson including decay correlations
We perform an analytic calculation of the one-loop amplitude for the W-boson
mediated process 0 \to d u-bar Q Q-bar l-bar l, retaining the mass for the
quark Q. The momentum of each of the massive quarks is expressed as the sum of
two massless momenta and the corresponding heavy quark spinor is expressed as a
sum of two massless spinors. Using a special choice for the heavy quark spinors
we obtain analytic expressions for the one-loop amplitudes which are amenable
to fast numerical evaluation. The full next-to-leading order (NLO) calculation
of hadron+hadron \to W(\to e nu) b b-bar with massive b-quarks is included in
the program MCFM. A comparison is performed with previous published work.Comment: 45 pages, 17 figure
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