739 research outputs found
Transverse-momentum resummation for heavy-quark hadroproduction
We consider the production of a pair of heavy quarks () in
hadronic collisions. When the transverse momentum of the heavy-quark pair
is much smaller than its invariant mass, the QCD perturbative expansion is
affected by large logarithmic terms that must be resummed to all-orders. This
behavior is well known from the simpler case of hadroproduction of colourless
high-mass systems, such as vector or Higgs boson(s). In the case of
production, the final-state heavy quarks carry colour charge and are
responsible for additional soft radiation (through direct emission and
interferences with initial-state radiation) that complicates the evaluation of
the logarithmically-enhanced terms in the small- region. We present the
all-order resummation structure of the logarithmic contributions, which
includes colour flow evolution factors due to soft wide-angle radiation.
Resummation is performed at the completely differential level with respect to
the kinematical variables of the produced heavy quarks. Soft-parton radiation
produces azimuthal correlations that are fully taken into account by the
resummation formalism. These azimuthal correlations are entangled with those
that are produced by initial-state collinear radiation. We present explicit
analytical results up to next-to-leading order and next-to-next-to-leading
logarithmic accuracy.Comment: Some comments expanded and references added. Version published on NP
A Comparison of Predictions for SM Higgs Boson Production at the LHC
This paper describes a comparison of most of the available predictions for
the cross section and transverse momentum distribution for a 125 GeV mass Higgs
at the LHC, including those from the PYTHIA and HERWIG parton shower Monte
Carlos and from four resummation calculations.Comment: 7 pages, submitted to proceedings of the Workshop on Physics at TeV
Colliders, Les Houches 200
Mechanical characterization of mortars used in the restoration of historical buildings: an operative atlas for maintenance and conservation
The complexity of the architectural and structural restoration of historical buildings requires a careful choice in the use of repair mortars compatible with the original materials of the existing building. It is important to set up an atlas of reference, compared to many mixtures of mortars and conglomerates, useful to support the operational choices in the project of restoration, recovery, and maintenance of historical buildings. The aim is also to encourage the use of local materials with a âshort supply chainâ, compatible with buildings and installed with traditional techniques. The research makes use of experimental bending, compression and elastic modulus tests on different mixtures of mortars. This paper describes some of the first results obtained so far, because the research is still underway for many different mixtures to test and catalog. The comparison between the data and the reference values that will be identified, will lead to set up a reference atlas of mechanical behavior of repair mortars in order to direct the design and operational choices in function of requirements and performance of specific cases in the field of the restoration of historical buildings
production at hadron colliders in NNLO QCD
We consider the production of pairs at hadron colliders. We report
on the first complete and fully differential computation of radiative
corrections at next-to-next-to-leading order in QCD perturbation theory. We
present selected numerical results for pp collisions at 7 TeV and compare them
to available LHC data. We find that the impact of the NNLO QCD corrections on
the fiducial cross section ranges between 4 and 15%, depending on the applied
cuts.Comment: Minor changes, version published on PL
Next to leading order evolution of SIDIS processes in the forward region
We compute the order quark initiated corrections to
semi-inclusive deep inelastic scattering extending the approach developed
recently for the gluon contributions. With these corrections we complete the
order QCD description of these processes, verifying explicitly the
factorization of collinear singularities. We also obtain the corresponding NLO
evolution kernels, relevant for the scale dependence of fracture functions. We
compare the non-homogeneous evolution effects driven by these kernels with
those obtained at leading order accuracy and discuss their phenomenological
implications.Comment: 18 pages, 4 ps figures, uses revtex4 and feynmf. Accepted for
publication in Nuclear Physics
Order-alpha_s^2 corrections to one-particle inclusive processes in DIS
We analyze the order- QCD corrections to semi-inclusive deep
inelastic scattering and present results for processes initiated by a gluon. We
focus in the most singular pieces of these corrections in order to obtain the
hitherto unknown NLO evolution kernels relevant for the non homogeneous QCD
scale dependence of these cross sections, and to check explicitly factorization
at this order. In so doing we discuss the prescription of overlapping
singularities in more than one variable.Comment: 16 pages, 9 eps figures. Uses revtex4 and feynm
Detachment analysis of dehumidified repair mortars applied to historical masonry walls
An innovative laboratory procedure for the pre-qualification of repair mortars is described. The tested mortars are suitable for use with new dehumidified plasters applied to historical masonry walls. Long-term plaster detachment frequently occurs because of the mechanical incompatibility of mortar. The procedure consists of the application of static loads to mixed stone block-mortar specimens with particular characteristics, in terms of geometry and adhesion at the interface. A numerical simulation based on the cohesive crack model was used to follow the experimental data, in order to describe the evolutionary phenomenon of detachment as a function of a small number of parameters. The methodology is currently being used at Sacro Monte di Varallo Special Natural Reserve (UNESCO heritage site) in Piedmont (Italy
production at hadron colliders in NNLO QCD
Charged gauge boson pair production at the Large Hadron Collider allows
detailed probes of the fundamental structure of electroweak interactions. We
present precise theoretical predictions for on-shell production that
include, for the first time, QCD effects up to next-to-next-to-leading order in
perturbation theory. As compared to next-to-leading order, the inclusive
cross section is enhanced by 9% at 7 TeV and 12% at 14 TeV. The
residual perturbative uncertainty is at the 3% level. The severe contamination
of the cross section due to top-quark resonances is discussed in
detail. Comparing different definitions of top-free production in the
four and five flavour number schemes, we demonstrate that top-quark resonances
can be separated from the inclusive cross section without significant
loss of theoretical precision.Comment: 7 pages, 3 figure
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