33 research outputs found
The Underlying Event in Herwig++
We review the modelling of multiple interactions in the event generator
Herwig++ and study implications of recent tuning efforts to LHC data. A crucial
ingredient to a successful description of minimum-bias and underlying-event
observables is a model for colour reconnection. Improvements to this model,
inspired by statistical physics, are presented.Comment: 4 pages, 3 figures. Contribution to the DIS 2012 proceeding
Novel approach to measure quark/gluon jets at the LHC
In this paper, we present a new proposal on how to measure quark/gluon jet
properties at the LHC. The measurement strategy takes advantage of the fact
that the LHC has collected data at different energies. Measurements at two or
more energies can be combined to yield distributions of any jet property
separated into quark and gluon jet samples on a statistical basis, without the
need for an independent event-by-event tag. We illustrate our method with a
variety of different angularity observables, and discuss how to narrow down the
search for the most useful observables.Comment: 20 pages, 30 figure
Towards a deep learning model for hadronization
Hadronization is a complex quantum process whereby quarks and gluons become hadrons. The widely used models of hadronization in event generators are based on physically inspired phenomenological models with many free parameters. We propose an alternative approach whereby neural networks are used instead. Deep generative models are highly flexible, differentiable, and compatible with graphical processing units. We make the first step towards a data-driven machine learning-based hadronization model. In that step, we replace a component of the hadronization model within the Herwig event generator (cluster model) with HADML, a computer code implementing a generative adversarial network. We show that a HADML is capable of reproducing the kinematic properties of cluster decays. Furthermore, we integrate it into Herwig to generate entire events that can be compared with the output of the public Herwig simulator as well as with dat
Joseph the MoUSE : Mouse Ultrasonic Sound Explorer
Joseph the MoUSE — Mouse Ultrasonic Sound Explorer (MoUSE) software aims to address the issue of manual analysis of recordings from experiments on rodents by introducing automatic techniques for ultrasonic vocalization (USV) detection. It combines deep learning (DL) methods with classical pattern recognition and computer graphics algorithms. During development, we used a dataset that consisted of recordings from real-world experiments in the open field. Recordings like these pose obstacles to automatic USV detection, one of which is the noise produced by mice in the experimental area or in nearby cages. Therefore, additionally, we conducted research and implemented de-noising methods along with detection algorithms. The project includes Python packages with algorithms for sound noise removal and USV detection, and provides a user-friendly graphical interface
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
Herwig 7.1 Release Note
A new release of the Monte Carlo event generator Herwig (version 7.1) is now
available. This version introduces a number of improvements, notably: multi-jet
merging with the dipole shower at LO and NLO QCD; a new model for soft
interactions and diffraction; improvements to mass effects and top decays in
the dipole shower, as well as a new tune of the hadronisation parameters.Comment: 7 pages, 7 figures. Herwig is available from
https://herwig.hepforge.org
On the breaking of collinear factorization in QCD
We investigate the breakdown of collinear factorization for non-inclusive
observables in hadron-hadron collisions. For pure QCD processes, factorization
is violated at the three-loop level and it has a structure identical to that
encountered previously in the case of super-leading logarithms. In particular,
it is driven by the non-commutation of Coulomb/Glauber gluon exchanges with
other soft exchanges. Beyond QCD, factorization may be violated at the two-loop
level provided that the hard subprocess contains matrix element contributions
with phase differences between different colour topologies.Comment: Version 2: minor improvements for journal publicatio
Herwig 7.2 release note
A new release of the Monte Carlo event generator Herwig (version 7.2) is now available. This version introduces a number of improvements over the major version 7.0, notably: multi-jet merging with the dipole shower at LO and NLO QCD; spin correlations in both the dipole and angular-ordered parton showers; an improved choice of evolution variable in the angular-ordered parton shower; improvements to mass effects and top decays in the dipole shower, improvements to the simulation of multiple-parton interactions, including diffractive processes; a new model for baryonic colour reconnection; improvements to strangeness production; as well as a new tune of the hadronisation parameters and support for generic Lorentz structures in BSM models. This article illustrates new features of versions 7.1 and 7.2
Colour reconnections in Herwig++
We describe the implementation details of the colour reconnection model in
the event generator Herwig++. We study the impact on final-state observables in
detail and confirm the model idea from colour preconfinement on the basis of
studies within the cluster hadronization model. Moreover, we show that the
description of minimum bias and underlying event data at the LHC is improved
with this model and present results of a tune to available data.Comment: 19 pages, 21 figures, 2 tables. Matches with published versio