9,231 research outputs found
Vector boson production at hadron colliders: a fully exclusive QCD calculation at NNLO
We consider QCD radiative corrections to the production of W and Z bosons in
hadron collisions. We present a fully exclusive calculation up to
next-to-next-to-leading order (NNLO) in QCD perturbation theory. To perform
this NNLO computation, we use a recently proposed version of the subtraction
formalism. The calculation includes the gamma-Z interference, finite-width
effects, the leptonic decay of the vector bosons and the corresponding spin
correlations. Our calculation is implemented in a parton level Monte Carlo
program. The program allows the user to apply arbitrary kinematical cuts on the
final-state leptons and the associated jet activity, and to compute the
corresponding distributions in the form of bin histograms. We show selected
numerical results at the Tevatron and the LHC.Comment: 7 pages, 3 ps figure
Universality of transverse-momentum resummation and hard factors at the NNLO
We consider QCD radiative corrections to the production of colourless
high-mass systems in hadron collisions. The logarithmically-enhanced
contributions at small transverse momentum are treated to all perturbative
orders by a universal resummation formula that depends on a single
process-dependent hard factor. We show that the hard factor is directly related
to the all-order virtual amplitude of the corresponding partonic process. The
direct relation is universal (process independent), and it is expressed by an
all-order factorization formula that we explicitly evaluate up to the
next-to-next-to-leading order (NNLO) in QCD perturbation theory. Once the NNLO
scattering amplitude is available, the corresponding hard factor is directly
determined: it controls NNLO contributions in resummed calculations at full
next-to-next-to-leading logarithmic accuracy, and it can be used in
applications of the q_T subtraction formalism to perform fully-exclusive
perturbative calculations up to NNLO. The universality structure of the hard
factor and its explicit NNLO form are also extended to the related formalism of
threshold resummation.Comment: References added. Version accepted for publication on NP
Threshold resummation at NLL accuracy and soft-virtual cross sections at NLO
We consider QCD radiative corrections to the production of colourless
high-mass systems in hadron collisions. We show that the recent computation of
the soft-virtual corrections to Higgs boson production at NLO [1] together
with the universality structure of soft-gluon emission can be exploited to
extract the general expression of the hard-virtual coefficient that contributes
to threshold resummation at NLL accuracy. The hard-virtual coefficient is
directly related to the process-dependent virtual amplitude through a universal
(process-independent) factorization formula that we explicitly evaluate up to
three-loop order. As an application, we present the explicit expression of the
soft-virtual NLO corrections for the production of an arbitrary colourless
system. In the case of the Drell-Yan process, we confirm the recent result of
Ref.[2].Comment: Slightly expanded text, one reference added, version published on NP
On the semiclassical limit of 4d spin foam models
We study the semiclassical properties of the Riemannian spin foam models with
Immirzi parameter that are constructed via coherent states. We show that in the
semiclassical limit the quantum spin foam amplitudes of an arbitrary
triangulation are exponentially suppressed, if the face spins do not correspond
to a discrete geometry. When they do arise from a geometry, the amplitudes
reduce to the exponential of i times the Regge action. Remarkably, the
dependence on the Immirzi parameter disappears in this limit.Comment: 32 pages, 5 figure
Polarized semi-inclusive electroweak structure functions at next-to-leading-order
We present a next-to-leading order (NLO) computation of the full set of
polarized and unpolarized electroweak semi-inclusive DIS (SIDIS) structure
functions, whose knowledge is crucial for a precise extraction of polarized
parton distributions. We focus on the phenomenology of the polarized structure
functions for the kinematical conditions that could be reached in an
Electron-Ion-Collider.
We show that the NLO corrections are sizeable, particularly in the small-
range. We test the sensitivity of these structure functions on certain quark
distributions and compare it to the situation of inclusive DIS and
electromagnetic SIDIS.Comment: 17 pages, 5 figure
Superconductivity and local non-centrosymmetricity in crystal lattices
Symmetry of the crystal lattice can be a determining factor for the structure
of Cooper pairs in unconventional superconductors. In this study we extend the
discussion of superconductivity in non-centrosymmetric materials to the case
when inversion symmetry is missing locally, but is present on a global level.
Concretely, we investigate the staggered non-centrosymmetricity within a
regular sublattice structure, in some analogy to the discussion of
superconductivity in antiferromagnetic systems. Three crystal structures are
analyzed in detail as illustrative examples for the extended classification of
Cooper-pairing channels. One of the cases may be relevant for the class of
iron-pnictide superconductors
Longitudinally Polarized Photoproduction of Inclusive Hadrons Beyond the Leading Order
We present a complete next-to-leading order QCD calculation for
single-inclusive large-pT hadron production in longitudinally polarized
lepton-nucleon collisions, consistently including ``direct'' and ``resolved''
photon contributions. This process could be studied experimentally at a future
polarized lepton-proton collider like eRHIC at BNL. We examine the sensitivity
of such measurements to the so far completely unknown parton content of
circularly polarized photons.Comment: 15 pages, 7 eps figure
Explicit LDP for a slowed RW driven by a symmetric exclusion process
We consider a random walk (RW) driven by a simple symmetric exclusion process (SSE). Rescaling the RW and the SSE in such a way that a joint hydrodynamic limit theorem holds we prove a joint path large deviation principle. The corresponding large deviation rate function can be split into two components, the rate function of the SSE and the one of the RW given the path of the SSE. These components have different structures (Gaussian and Poissonian, respectively) and to overcome this difficulty we make use of the theory of Orlicz spaces. In particular, the component of the rate function corresponding to the RW is explicit.</p
An exploratory social network analysis of academic research networks
For several decades, academics around the world have been collaborating with the view to support the development of their research domain. Having said that, the majority of scientific and technological policies try to encourage the creation of strong inter-related research groups in order to improve the efficiency of research outcomes and subsequently research funding allocation. In this paper, we attempt to highlight and thus, to demonstrate how these collaborative networks are developing in practice. To achieve this, we have developed an automated tool for extracting data about joint article publications and analyzing them from the perspective of social network analysis. In this case study, we have limited data from works published in 2010 by England academic and research institutions. The outcomes of this work can help policy makers in realising the current status of research collaborative networks in England
Irreducible Killing Tensors from Third Rank Killing-Yano Tensors
We investigate higher rank Killing-Yano tensors showing that third rank
Killing-Yano tensors are not always trivial objects being possible to construct
irreducible Killing tensors from them. We give as an example the Kimura IIC
metric were from two rank Killing-Yano tensors we obtain a reducible Killing
tensor and from third rank Killing-Yano tensors we obtain three Killing
tensors, one reducible and two irreducible.Comment: 10 page
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