4,876 research outputs found
Multi-jet production in lepton-proton scattering at next-to-leading order accuracy
I summarize the theoretical and experimental status of multijet production in
DIS. I present the state of the art theoretical predictions and compare those
to the corresponding experimental results obtained by analysing the data
collected by the H1 and ZEUS collaborations at HERA. I also show new
predictions for three-jet event-shape distributions at the NLO accuracy.Comment: 11 pages, 8 figures. To appear in the proceedings of the Ringberg
Workshop on "New Trends in HERA Physics 2005", Ringberg Castle, Tegernsee,
Germany, 2-7 October 200
Separation of soft and collinear infrared limits of QCD squared matrix elements
We present a simple way of separating the overlap between the soft and
collinear factorization formulae of QCD squared matrix elements. We check its
validity explicitly for single and double unresolved emissions of tree-level
processes. The new method makes possible the definition of helicity-dependent
subtraction terms for regularizing the real contributions in computing
radiative corrections to QCD jet cross sections. This implies application of
Monte Carlo helicity summation in computing higher order corrections.Comment: 14 pages, 1 figure, references adde
Hadroproduction of at NLO accuracy matched with shower Monte Carlo programs
We present the computation of the differential cross section for the process
at NLO QCD accuracy
matched to Shower Monte Carlo (SMC) simulations using PowHel, on the basis of
the interface between HELAC-NLO and POWHEG-BOX. We include all resonant and
non-resonant contributions. This is achieved by fully taking into account the
effect of off-shell t-quarks and off-shell W-bosons in the complex mass scheme.
We also present a program called DECAYER that can be used to let the t-quarks
present in the event files for processes
decay including both the finite width of the t-quarks and spin correlations. We
present predictions for both the Tevatron and the LHC, with emphasis on
differences emerging from three different
hadroproduction computations: (i) full implementation of the process, (ii) generating on-shell t-quarks pushed
off-shell with a Breit-Wigner finite width and decayed by DECAYER, and (iii)
on-shell t-quark production followed by decay in the narrow width
approximation, as described by the SMC.Comment: 40 pages, 26 figures; slightly expanded version matching the one
published in JHE
Integration of collinear-type doubly unresolved counterterms in NNLO jet cross sections
In the context of a subtraction method for jet cross sections at NNLO
accuracy in the strong coupling, we perform the integration over the
two-particle factorised phase space of the collinear-type contributions to the
doubly unresolved counterterms. We present the final result as a convolution in
colour space of the Born cross section and of an insertion operator, which is
written in terms of master integrals that we expand in the dimensional
regularisation parameter.Comment: 47 page
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