122 research outputs found
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
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
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
QCD and studies at FCC-ee
The Future Circular Collider (FCC) is a post-LHC project aiming at searches
for physics beyond the SM in a new 80--100~km tunnel at CERN. Running in its
first phase as a very-high-luminosity electron-positron collider (FCC-ee), it
will provide unique possibilities for indirect searches of new phenomena
through high-precision tests of the SM. In addition, by collecting tens of
ab integrated luminosity in the range of center-of-mass energies
~=90--350~GeV, the FCC-ee also offers unique physics opportunities
for precise measurements of QCD phenomena and of photon-photon collisions
through, literally, billions of hadronic final states as well as unprecedented
large fluxes of quasireal 's radiated from the beams. We
succinctly summarize the FCC-ee perspectives for high-precision extractions of
the QCD coupling, for detailed analyses of parton radiation and fragmentation,
and for SM and BSM studies through collisions.Comment: 6 pages, Proceedings ICHEP'16 (Chicago
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
A framework for second-order parton showers
A framework is presented for including second-order perturbative corrections
to the radiation patterns of parton showers. The formalism allows to combine
O(alphaS^2)-corrected iterated 2->3 kernels for "ordered" gluon emissions with
tree-level 2->4 kernels for "unordered" ones. The combined Sudakov evolution
kernel is thus accurate to O(alphaS^2). As a first step towards a full-fledged
implementation of these ideas, we develop an explicit implementation of 2->4
shower branchings in this letter.Comment: 11 pages, 3 figure
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
A Brief Introduction to PYTHIA 8.1
The PYTHIA program is a standard tool for the generation of high-energy
collisions, comprising a coherent set of physics models for the evolution from
a few-body hard process to a complex multihadronic final state. It contains a
library of hard processes and models for initial- and final-state parton
showers, multiple parton-parton interactions, beam remnants, string
fragmentation and particle decays. It also has a set of utilities and
interfaces to external programs. While previous versions were written in
Fortran, PYTHIA 8 represents a complete rewrite in C++. The current release is
the first main one after this transition, and does not yet in every respect
replace the old code. It does contain some new physics aspects, on the other
hand, that should make it an attractive option especially for LHC physics
studies.Comment: 27 page
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