68 research outputs found
Rare Standard Model processes for present and future hadronic colliders
In this talk I present the total cross sections, accurate at the NLO in QCD,
for rare Standard-Model hadroproduction processes involving multi-Higgs-boson,
multi-electroweak-boson and multi-top-quark final states. The comparison
between cross sections at the LHC and at a future circular hadronic collider
with up to 100 TeV centre-of-mass energy is detailed. Results relevant to the
hadronic production of five electroweak bosons, and of a top-antitop pair in
association with an electroweak vector boson and two jets are presented here
for the first time with NLO accuracy
Towards analytic local sector subtraction at NNLO
A new method for local subtraction at next-to-next-to-leading order in QCD is
sketched, attempting to conjugate the minimal counterterm structure arising
from a sector partition of the radiation phase space with the simplifications
following from analytic integration of the counterterms.Comment: 10 pages, contribution to the proceedings of `RADCOR 2017', St.
Gilgen (Austria), September 201
A new way of reducing negative weights in MC@NLO
We introduce a new technique, that we dub Born spreading, aimed at reducing
the number of negative-weight events in the MC@NLO matching of NLO
calculations with parton-shower simulations. We show that such a technique,
based on a re-distribution of Born matrix elements in the radiative phase
space, achieves a sizeable reduction of negative-weight events at little
computational cost. The method does not induce any biases in physical
distributions.Comment: 5 pages, 1 tabl
Momentum-space resummation for transverse observables and the Higgs at NLL+NNLO
We present an approach to the momentum-space resummation of global, recursive
infrared and collinear safe observables featuring kinematic zeros away from the
Sudakov limit. In the hadro-production of a generic colour singlet, we consider
the family of inclusive observables which do not depend on the rapidity of the
radiation, prime examples being the transverse momentum of the singlet, and
in Drell-Yan pair production. We derive a resummation formula valid up
to next-to-next-to-next-to-leading-logaritmic accuracy for the considered
observables. This formula reduces exactly to the customary resummation
performed in impact-parameter space in the known cases, and it also predicts
the correct power-behaved scaling of the cross section in the limit of small
value of the observable. We show how this formalism is efficiently implemented
by means of Monte Carlo techniques in a fully exclusive generator that allows
one to apply arbitrary cuts on the Born variables for any colour singlet, as
well as to automatically match the resummed results to fixed-order
calculations. As a phenomenological application, we present state-of-the-art
predictions for the Higgs-boson transverse-momentum spectrum at the LHC at
next-to-next-to-next-to-leading-logarithmic accuracy matched to fixed
next-to-next-to-leading order.Comment: Journal versio
The Z\gamma{} transverse-momentum spectrum at NNLO+N3LL
We consider the transverse-momentum () distribution of pairs
produced in hadronic collisions. Logarithmically enhanced contributions at
small are resummed to all orders in QCD perturbation theory and combined
with the fixed-order prediction. We achieve the most advanced prediction for
the spectrum by matching next-to-next-to-next-to-leading
logarithmic (NLL) resummation to the integrated cross section at
next-to-next-to-leading order (NNLO). By considering
production at the fully differential level, including spin correlations,
interferences and off-shell effects, arbitrary cuts can be applied to the
leptons and the photon. We present results at the LHC in presence of fiducial
cuts and find agreement with the \,TeV ATLAS data at the few-percent level.Comment: 16 pages, 7 figures, 1 tabl
The MC@NLO 4.0 Event Generator
This is the user's manual of MC@NLO 4.0. This package is a practical
implementation, based upon the Fortran HERWIG and Herwig++ event generators, of
the MC@NLO formalism, which allows one to incorporate NLO QCD matrix elements
consistently into a parton shower framework. Processes available in this
version include the hadroproduction of single vector and Higgs bosons, vector
boson pairs, heavy quark pairs, single top, single top in association with a W,
single top in association with a charged Higgs in type I or II 2HDM models,
lepton pairs, and Higgs bosons in association with a W or Z. Spin correlations
are included for all processes except ZZ production. This document is
self-contained, but we emphasise the main differences with respect to previous
versions.Comment: 36 pages, no figure
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