374 research outputs found
Scale Evolution of Unintegrated Distributions and the p_t Spectrum of Gauge Bosons
We present predictions for the -boson -spectrum at Tevatron within
the framework of unintegrated distributions evolved according to evolution
equations recently proposed by us. We discuss the dependence of the results on
the choice of non-perturbative parameters, the coupling constant and the impact
of soft gluon resummation.Comment: proceedings of the workshop "Recent Advances in Perturbative QCD and
Hadronic Physics", 20-25 July 2009, ECT*, Trento (Italy), in Honor of Prof.
Anatoly Efremov's 75th Birthday Celebratio
A Positive-Weight Next-to-Leading-Order Monte Carlo for e+e- Annihilation to Hadrons
We apply the positive-weight Monte Carlo method of Nason for simulating QCD
processes accurate to Next-To-Leading Order to the case of e+e- annihilation to
hadrons. The method entails the generation of the hardest gluon emission first
and then subsequently adding a `truncated' shower before the emission. We have
interfaced our result to the Herwig++ shower Monte Carlo program and obtained
better results than those obtained with Herwig++ at leading order with a matrix
element correction.Comment: 21 pages, 11 figures, 2 tables Reason for replacement: minor
corrections, typos and 1 changed referenc
A model of non-perturbative gluon emission in an initial state parton shower
We consider a model of transverse momentum production in which
non-perturbative smearing takes place throughout the perturbative evolution, by
a simple modification to an initial state parton shower algorithm. Using this
as the important non-perturbative ingredient, we get a good fit to data over a
wide range of energy. Combining it with the non-perturbative masses and cutoffs
that are a feature of conventional parton showers also leads to a reasonable
fit. We discuss the extrapolation to the LHC.Comment: 14 pages, 6 figures; version accepted by JHE
The Photon Wave Function in Non-forward Diffractive Scattering with Non-vanishing Quark Masses
The light-cone Photon wave function in explicit helicity states, valid for
massive quarks and in both momentum and configuration space, is presented by
considering the leading order photon-proton hard scattering, i.e., the
splitting quark pair scatters with the proton in the Regge limit. Further we
apply it to the diffractive scattering at nonzero momentum transfer and reach a
similar factorization as in the case of zero momentum transfer.Comment: 11 pages LaTeX, 2 figures, version to appear in Phys. Rev.
New formalism for QCD parton showers
We present a new formalism for parton shower simulation of QCD jets, which
incorporates the following features: invariance under boosts along jet axes,
improved treatment of heavy quark fragmentation, angular-ordered evolution with
soft gluon coherence, more accurate soft gluon angular distributions, and
better coverage of phase space. It is implemented in the new HERWIG++ event
generator
Soft and diffractive scattering with the cluster model in Herwig
We present a new model for soft interactions in the event-generator Herwig. The model consists of two components. One to model diffractive final states on the basis of the cluster hadronization model and a second component that addresses soft multiple interactions as multiple particle production in multiperipheral kinematics. We present much improved results for minimum-bias measurements at various LHC energies
The Process \gamma^{*}_L+ q \to q\bar{q}g + q: Real Corrections to the Virtual Photon Impact Factor
We calculate, for the longitudinally polarized virtual photon, the cross
section of the process \gamma^{*}+q\to (q\bar{q}g)+q at high energies with a
large rapidity gap between the fragmentation system q\bar{q}g and the other
quark. This process provides the real corrections of the virtual photon impact
factor in the next-to leading order. Evidence is given for the appearance of a
new q\bar{q}g Fock-component of the photon state.Comment: 17 pages, 4 figures, revte
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A positive-weight next-to-leading-order Monte Carlo for e<sup>+</sup>e <sup>-</sup> annihilation to hadrons
We apply the positive-weight Monte Carlo method of Nason for simulating QCD
processes accurate to Next-To-Leading Order to the case of e+e- annihilation to
hadrons. The method entails the generation of the hardest gluon emission first
and then subsequently adding a `truncated' shower before the emission. We have
interfaced our result to the Herwig++ shower Monte Carlo program and obtained
better results than those obtained with Herwig++ at leading order with a matrix
element correction
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