169 research outputs found
Differential Cross Sections for Higgs Production
We review recent theoretical progress in evaluating higher order QCD
corrections to Higgs boson differential distributions at hadron-hadron
colliders
Stochastic evolution equations driven by Liouville fractional Brownian motion
Let H be a Hilbert space and E a Banach space. We set up a theory of
stochastic integration of L(H,E)-valued functions with respect to H-cylindrical
Liouville fractional Brownian motions (fBm) with arbitrary Hurst parameter in
the interval (0,1). For Hurst parameters in (0,1/2) we show that a function
F:(0,T)\to L(H,E) is stochastically integrable with respect to an H-cylindrical
Liouville fBm if and only if it is stochastically integrable with respect to an
H-cylindrical fBm with the same Hurst parameter. As an application we show that
second-order parabolic SPDEs on bounded domains in \mathbb{R}^d, driven by
space-time noise which is white in space and Liouville fractional in time with
Hurst parameter in (d/4,1) admit mild solution which are H\"older continuous
both and space.Comment: To appear in Czech. Math.
Parton distribution functions from the precise NNLO QCD fit
We report the parton distribution functions (PDFs) determined from the NNLO
QCD analysis of the world inclusive DIS data with account of the precise NNLO
QCD corrections to the evolution equations kernel. The value of strong coupling
constant \alpha_s^{NNLO}(M_Z)=0.1141(14), in fair agreement with one obtained
using the earlier approximate NNLO kernel by van Neerven-Vogt. The intermediate
bosons rates calculated in the NNLO using obtained PDFs are in agreement to the
latest Run II results.Comment: 8 pages, LATEX, 2 figures (EPS
Canonical Quantisation in n.A=0 gauges
We give a unified derivation of the propagator in the gauges for
timelike, spacelike or lightlike. We discuss the physical states and
other physical questions.Comment: 7 pages, DAMTP 93-33, ITP-SB-93-3
Isospin Dependence of Power Corrections in Deep Inelastic Scattering
We present results of a perturbative QCD analysis of deep inelastic
measurements of both the deuteron and proton structure functions. We evaluate
the theoretical uncertainty associated to nuclear effects in the deuteron, and
we extract simultaneously the isospin depedendence of: i)the higher twists
terms; ii) the ratio of the longitudinal to transverse cross sections; iii) the
ratio of the neutron to proton structure functions. The extraction of the
latter, in particular, has been at the center of an intense debate. Its
accurate determination is crucial both theoretically and for the interpretation
of the more precise neutrino experiments including the newly planned high
intensity 50 GeV proton synchrotron.Comment: 33 pages, 16 figure
Next-to-Next-to-Leading Order Higgs Production at Hadron Colliders
The Higgs boson production cross section at pp and p\bar{p} colliders is
calculated in QCD at next-to-next-to-leading order (NNLO). We find that the
perturbative expansion of the production cross section is well behaved and that
scale dependence is reduced relative to the NLO result. These findings give us
confidence in the reliability of the prediction. We also report an error in the
NNLO correction to Drell-Yan production.Comment: 5 pages, 4 figures, minor change
QCD and Yukawa corrections to single-top-quark production via q qbar -> t bbar
We calculate the O(alpha_s) and O(alpha_W m_t^2/M_W^2) corrections to the
production of a single top quark via the weak process q qbar -> t bbar at the
Fermilab Tevatron and the CERN Large Hadron Collider. An accurate calculation
of the cross section is necessary in order to extract |V_tb| from experiment.Comment: LaTeX, 13 pages, replaced with version to appear in Phys. Rev.
High-precision QCD at hadron colliders: electroweak gauge boson rapidity distributions at NNLO
We compute the rapidity distributions of W and Z bosons produced at the
Tevatron and the LHC through next-to-next-to leading order in QCD. Our results
demonstrate remarkable stability with respect to variations of the
factorization and renormalization scales for all values of rapidity accessible
in current and future experiments. These processes are therefore
``gold-plated'': current theoretical knowledge yields QCD predictions accurate
to better than one percent. These results strengthen the proposal to use W and
Z production to determine parton-parton luminosities and constrain parton
distribution functions at the LHC. For example, LHC data should easily be able
to distinguish the central parton distribution fit obtained by MRST from that
obtained by Alekhin.Comment: 47 pages, 17 figures. Minor typos, 1 reference correcte
Electroweak radiative corrections to W-boson production at hadron colliders
The complete set of electroweak O(alpha) corrections to the Drell--Yan-like
production of W bosons is calculated and compared to an approximation provided
by the leading term of an expansion about the W-resonance pole. All relevant
formulae are listed explicitly, and particular attention is paid to issues of
gauge invariance and the instability of the W bosons. A detailed discussion of
numerical results underlines the phenomenological importance of the electroweak
corrections to W-boson production at the Tevatron and at the LHC. While the
pole expansion yields a good description of resonance observables, it is not
sufficient for the high-energy tail of transverse-momentum distributions,
relevant for new-physics searches.Comment: 29 pages, latex, 17 postscript files, revised version that is to
appear in Phys.Rev.D, some explanations added and results extended by a
discussion of the QED factorization scale dependenc
Infinities within graviton scattering amplitudes
We present unitarity as a method for determining the infinities present in
graviton scattering amplitudes. The infinities are a combination of IR and UV.
By understanding the soft singularities we may extract the UV infinities and
relate these to counter-terms in the effective action. As an demonstration of
this method we rederive the UV infinities present at one-loop when gravity is
coupled to matter.Comment: revised versio
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