271 research outputs found
CEDAR: tools for event generator tuning
I describe the work of the CEDAR collaboration in developing tools for tuning
and validating Monte Carlo event generator programs. The core CEDAR task is to
interface the Durham HepData database of experimental measurements to event
generator validation tools such as the UCL JetWeb system - this has
necessitated the migration of HepData to a new relational database system and a
Java-based interaction model. The "number crunching" part of JetWeb is also
being upgraded, from the Fortran HZTool library to the new C++ Rivet system and
a generator interfacing layer named RivetGun. Finally, I describe how Rivet is
already being used as a central part of a new generator tuning system, and
summarise two other CEDAR activities, HepML and HepForge.Comment: 13 pages, prepared for XI International Workshop on Advanced
Computing and Analysis Techniques in Physics Research, Amsterdam, April 23-27
200
Tuning of MC generator MPI models
MC models of multiple partonic scattering inevitably introduce many free
parameters, either fundamental to the models or from their integration with MC
treatments of primary-scattering evolution. This non-perturbative and
non-factorisable physics in particular cannot currently be constrained from
theoretical principles, and hence parameter optimisation against experimental
data is required. This process is commonly referred to as MC tuning. We
summarise the principles, problems and history of MC tuning, and the
still-evolving modern approach to both model optimisation and estimation of
modelling uncertainties.Comment: Contributed chapter to "Multiple Parton Interactions at the LHC",
World Scientific 201
HepData reloaded: reinventing the HEP data archive
We describe the status of the HepData database system, following a major
re-development in time for the advent of LHC data. The new HepData system
benefits from use of modern database and programming language technologies, as
well as a variety of high-quality tools for interfacing the data sources and
their presentation, primarily via the Web. The new back-end provides much more
flexible and semantic data representations than before, on which new external
applications can be built to respond to the data demands of the LHC
experimental era. The HepData re-development was largely motivated by a desire
to have a single source of reference data for Monte Carlo validation and tuning
tools, whose status and connection to HepData we also briefly review.Comment: 7 pages, 3 figures, Presented at 13th International Workshop on
Advanced Computing and Analysis Techniques in Physics Research (ACAT 2010),
February 22-27, 2010, Jaipur, Indi
QCD-aware partonic jet clustering for truth-jet flavour labelling
We present an algorithm for deriving partonic flavour labels to be applied to
truth particle jets in Monte Carlo event simulations. The inputs to this
approach are final pre-hadronization partons, to remove dependence on
unphysical details such as the order of matrix element calculation and shower
generator frame recoil treatment. These are clustered using standard jet
algorithms, modified to restrict the allowed pseudojet combinations to those in
which tracked flavour labels are consistent with QCD and QED Feynman rules. The
resulting algorithm is shown to be portable between the major families of
shower generators, and largely insensitive to many possible systematic
variations: it hence offers significant advantages over existing ad hoc
labelling schemes. However, it is shown that contamination from multi-parton
scattering simulations can disrupt the labelling results. Suggestions are made
for further extension to incorporate more detailed QCD splitting function
kinematics, robustness improvements, and potential uses for truth-level physics
object definitions and tagging
Computational challenges for MC event generation
The sophistication of fully exclusive MC event generation has grown at an
extraordinary rate since the start of the LHC era, but has been mirrored by a
similarly extraordinary rise in the CPU cost of state-of-the-art MC
calculations. The reliance of experimental analyses on these calculations
raises the disturbing spectre of MC computations being a leading limitation on
the physics impact of the HL-LHC, with MC trends showing more signs of further
cost-increases rather than the desired speed-ups. I review the methods and
bottlenecks in MC computation, and areas where new computing architectures,
machine-learning methods, and social structures may help to avert calamity.Comment: Based on a plenary talk at ACAT 201
PySLHA: a Pythonic interface to SUSY Les Houches Accord data
This paper describes the PySLHA package, a Python language module and program
collection for reading, writing and visualising SUSY model data in the SLHA
format. PySLHA can read and write SLHA data in a very general way, including
the official SLHA2 extension and user customisations, and with arbitrarily deep
indexing of data block entries and a dedicated, intuitive interface for
particle data and decay information. PySLHA can additionally read and write the
legacy ISAWIG model format, and provides format conversion scripts. The draft
SLHA3 XSECTION feature is also fully supported. A publication-quality mass
spectrum & decay chain plotting tool, slhaplot, is also included.Comment: 7 pages. Original submission 2013, updated 2015 for version 3.1 with
XSECTION suppor
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
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