17,298 research outputs found
QCD (&) Event Generators
Recent developments in QCD phenomenology have spurred on several improved
approaches to Monte Carlo event generation, relative to the post--LEP state of
the art. In this brief review, the emphasis is placed on approaches for 1)
consistently merging fixed--order matrix element calculations with parton
showers, 2) improving the parton shower algorithms themselves, and 3) improving
the description of the underlying event in hadron collisions.Comment: Submitted to proceedings of DIS05, 12 page
Soft-QCD and UE spectra in pp collisions at very high CM energies (a Snowmass white paper)
We make some educated guesses for the extrapolations of typical
soft-inclusive (minimum-bias, pileup, underlying-event) observables to
proton-proton collisions at center-of-mass energies in the range 13 - 100 TeV.
The numbers should be interpreted with (at least) a 10% uncertainty.Comment: 5 pages. Update (v2) adds numbers for 13 TeV and corrects bug in UE
ET density estimate
A Quick Guide to SUSY Tools
The last decade has seen the emergence of a wide range of automated
calculations for supersymmetric extensions of the Standard Model. This guide
contains a brief summary of these, with the main focus on hadron collider
phenomenology, as well as a brief introduction to the so-called SUSY Les
Houches Accord. See also the Les Houches Web Repository for BSM Tools:
http://www.ippp.dur.ac.uk/montecarlo/BSM/Comment: 6 pages. Prepared for the TeV4LHC Physics Landscapes summary repor
Non-perturbative QCD Effects and the Top Mass at the Tevatron
The modelling of non-perturbative effects is an important part of modern
collider physics simulations. In hadron collisions there is some indication
that the modelling of the interactions of the beam remnants, the underlying
event, may require non-trivial colour reconnection effects to be present. We
recently introduced a universally applicable toy model of such reconnections,
based on hadronising strings. This model, which has one free parameter, has
been implemented in the Pythia event generator. We then considered several
parameter sets (`tunes'), constrained by fits to Tevatron minimum-bias data,
and determined the sensitivity of a simplified top mass analysis to these
effects, in exclusive semi-leptonic top events at the Tevatron. A first attempt
at isolating the genuine non-perturbative effects gave an estimate of order
+-0.5GeV from non-perturbative uncertainties. The results presented here are an
update to the original study and include recent bug fixes of Pythia that
influenced the tunings investigated.Comment: 8 pages, 5 figures, Submitted to the Proceedings of Top2008, 18-24
May 2008, La Biodola, Isola d'Elba, Ital
Strange Particles and Neutron Stars - Experiments at Gsi
Experiments on strangeness production in nucleus-nucleus collisions at SIS
energies address fundamental aspects of modern nuclear physics: the
determination of the nuclear equation-of-state at high baryon densities and the
properties of hadrons in dense nuclear matter. Experimental data and
theoretical results will be reviewed. Future experiments at the FAIR
accelerator aim at the exploration of the QCD phase diagram at highest baryon
densities.Comment: %Invited talk given at the International Invited talk given at the
International Symposium on Heavy Ion Physics (ISHIP 2006) April 3-6 2006,
FIAS, Frankfurt, Germany Frankfurt, German
String Formation Beyond Leading Colour
We present a new model for the hadronisation of multi-parton systems, in
which colour correlations beyond leading are allowed to influence the
formation of confining potentials (strings). The multiplet structure of
is combined with a minimisation of the string potential energy, to decide
between which partons strings should form, allowing also for "baryonic"
configurations (e.g., two colours can combine coherently to form an
anticolour). In collisions, modifications to the leading-colour picture
are small, suppressed by both colour and kinematics factors. But in
collisions, multi-parton interactions increase the number of possible
subleading connections, counteracting their naive suppression.
Moreover, those that reduce the overall string lengths are kinematically
favoured. The model, which we have implemented in the PYTHIA 8 generator, is
capable of reaching agreement not only with the important
\left(n_\mathrm{charged}) distribution but also with measured
rates (and ratios) of kaons and hyperons, in both and collisions.
Nonetheless, the shape of their spectra remains challenging to
explain.Comment: 48 pages, 22 figure
Genuinely sharp heat kernel estimates on compact rank-one symmetric spaces, for Jacobi expansions, on a ball and on a simplex
We prove genuinely sharp two-sided global estimates for heat kernels on all
compact rank-one symmetric spaces. This generalizes the authors' recent result
obtained for a Euclidean sphere of arbitrary dimension. Furthermore, similar
heat kernel bounds are shown in the context of classical Jacobi expansions, on
a ball and on a simplex. These results are more precise than the qualitatively
sharp Gaussian estimates proved recently by several authors.Comment: 16 page
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