18 research outputs found
Monte Carlo event generator validation and tuning for the LHC
We summarise the motivation for, and the status of, the tools developed by
CEDAR/MCnet for validating and tuning Monte Carlo event generators for the LHC
against data from previous colliders. We then present selected preliminary
results from studies of event shapes and hadronisation observables from e+e-
colliders, and of minimum bias and underlying event observables from the
Tevatron, and comment on the approach needed with early LHC data to best
exploit the potential for new physics discoveries at the LHC in the next few
years.Comment: Prepared for Proceedings of XII Advanced Computing and Analysis
Techniques in Physics Research, November 3-7 2008, Erice, Ital
New developments in event generator tuning techniques
Data analyses in hadron collider physics depend on background simulations
performed by Monte Carlo (MC) event generators. However, calculational
limitations and non-perturbative effects require approximate models with
adjustable parameters. In fact, we need to simultaneously tune many
phenomenological parameters in a high-dimensional parameter-space in order to
make the MC generator predictions fit the data. It is desirable to achieve this
goal without spending too much time or computing resources iterating parameter
settings and comparing the same set of plots over and over again. We present
extensions and improvements to the MC tuning system, Professor, which addresses
the aforementioned problems by constructing a fast analytic model of a MC
generator which can then be easily fitted to data. Using this procedure it is
for the first time possible to get a robust estimate of the uncertainty of
generator tunings. Furthermore, we can use these uncertainty estimates to study
the effect of new (pseudo-) data on the quality of tunings and therefore decide
if a measurement is worthwhile in the prospect of generator tuning. The
potential of the Professor method outside the MC tuning area is presented as
well.Comment: To appear in the proceedings of the 13th International Workshop on
Advanced Computing and Analysis Techniques in Physics Research, ACAT2010,
Jaipur, India, February 22-27, 201
Systematic event generator tuning for the LHC
In this article we describe Professor, a new program for tuning model
parameters of Monte Carlo event generators to experimental data by
parameterising the per-bin generator response to parameter variations and
numerically optimising the parameterised behaviour. Simulated experimental
analysis data is obtained using the Rivet analysis toolkit. This paper presents
the Professor procedure and implementation, illustrated with the application of
the method to tunes of the Pythia 6 event generator to data from the LEP/SLD
and Tevatron experiments. These tunes are substantial improvements on existing
standard choices, and are recommended as base tunes for LHC experiments, to be
themselves systematically improved upon when early LHC data is available.Comment: 28 pages. Submitted to European Physical Journal C. Program sources
and extra information are available from
http://projects.hepforge.org/professor
Systematic improvement of QCD parton showers
In this contribution, we will give a brief overview of the progress that has
been achieved in the field of combining matrix elements and parton showers. We
exemplify this by focusing on the case of electron--positron collisions and by
reporting on recent developments as accomplished within the Sherpa event
generation framework.Comment: 6 figures, to appear in the proceedings of Linear Collider 2011
(Understanding QCD at linear colliders in searching for old and new physics),
12--16 September 2011, ECT*, Trento, Ital