5,879 research outputs found
Lessons for SUSY from the LHC after the first run
A review of direct searches for new particles predicted by Supersymmetry
after the first run of the LHC is proposed. This review is based on the results
provided by the ATLAS and CMS experiments.Comment: 31 pages, 41 figures, Appear in the special issue of the EPJ C
journal entitled "SUSY after the Higgs discovery
Performance and optimization of support vector machines in high-energy physics classification problems
In this paper we promote the use of Support Vector Machines (SVM) as a
machine learning tool for searches in high-energy physics. As an example for a
new- physics search we discuss the popular case of Supersymmetry at the Large
Hadron Collider. We demonstrate that the SVM is a valuable tool and show that
an automated discovery- significance based optimization of the SVM
hyper-parameters is a highly efficient way to prepare an SVM for such
applications. A new C++ LIBSVM interface called SVM-HINT is developed and
available on Github.Comment: 20 pages, 6 figure
Attention to Mean-Fields for Particle Cloud Generation
The generation of collider data using machine learning has emerged as a
prominent research topic in particle physics due to the increasing
computational challenges associated with traditional Monte Carlo simulation
methods, particularly for future colliders with higher luminosity. Although
generating particle clouds is analogous to generating point clouds, accurately
modelling the complex correlations between the particles presents a
considerable challenge. Additionally, variable particle cloud sizes further
exacerbate these difficulties, necessitating more sophisticated models. In this
work, we propose a novel model that utilizes an attention-based aggregation
mechanism to address these challenges. The model is trained in an adversarial
training paradigm, ensuring that both the generator and critic exhibit
permutation equivariance/invariance with respect to their input. A novel
feature matching loss in the critic is introduced to stabilize the training.
The proposed model performs competitively to the state-of-art whilst having
significantly fewer parameters
Point Cloud Generation using Transformer Encoders and Normalising Flows
Data generation based on Machine Learning has become a major research topic
in particle physics. This is due to the current Monte Carlo simulation approach
being computationally challenging for future colliders, which will have a
significantly higher luminosity. The generation of collider data is similar to
point cloud generation, but arguably more difficult as there are complex
correlations between the points which need to be modelled correctly. A
refinement model consisting of normalising flows and transformer encoders is
presented. The normalising flow output is corrected by a transformer encoder,
which is adversarially trained against another transformer encoder
discriminator/critic. The model reaches state-of-the-art performance while
yielding a stable training
Non-Simplified SUSY: Stau-Coannihilation at LHC and ILC
If new phenomena beyond the Standard Model will be discovered at the LHC, the
properties of the new particles could be determined with data from the
High-Luminosity LHC and from a future linear collider like the ILC. We discuss
the possible interplay between measurements at the two accelerators in a
concrete example, namely a full SUSY model which features a small stau_1-LSP
mass difference. Various channels have been studied using the Snowmass 2013
combined LHC detector implementation in the Delphes simulation package, as well
as simulations of the ILD detector concept from the Technical Design Report. We
investigate both the LHC and ILC capabilities for discovery, separation and
identification of various parts of the spectrum. While some parts would be
discovered at the LHC, there is substantial room for further discoveries at the
ILC. We finally highlight examples where the precise knowledge about the lower
part of the mass spectrum which could be acquired at the ILC would enable a
more in-depth analysis of the LHC data with respect to the heavier states.Comment: 42 pages, 18 figures, 12 table
JetFlow: Generating Jets with Conditioned and Mass Constrained Normalising Flows
Fast data generation based on Machine Learning has become a major research
topic in particle physics. This is mainly because the Monte Carlo simulation
approach is computationally challenging for future colliders, which will have a
significantly higher luminosity. The generation of collider data is similar to
point cloud generation with complex correlations between the points.
In this study, the generation of jets with up to 30 constituents with
Normalising Flows using Rational Quadratic Spline coupling layers is
investigated. Without conditioning on the jet mass, our Normalising Flows are
unable to model all correlations in data correctly, which is evident when
comparing the invariant jet mass distributions between ground truth and
generated data. Using the invariant mass as a condition for the coupling
transformation enhances the performance on all tracked metrics. In addition, we
demonstrate how to sample the original mass distribution by interpolating the
empirical cumulative distribution function. Similarly, the variable number of
constituents is taken care of by introducing an additional condition on the
number of constituents in the jet.
Furthermore, we study the usefulness of including an additional mass
constraint in the loss term. On the \texttt{JetNet} dataset, our model shows
state-of-the-art performance combined with fast and stable training
Heavy Scalar Top Quark Decays in the Complex MSSM: A Full One-Loop Analysis
We evaluate all two-body decay modes of the heavy scalar top quark in the
Minimal Supersymmetric Standard Model with complex parameters (cMSSM) and no
generation mixing. The evaluation is based on a full one-loop calculation of
all decay channels, also including hard QED and QCD radiation. The
renormalization of the complex parameters is described in detail. The
dependence of the heavy scalar top quark decay on the relevant cMSSM parameters
is analyzed numerically, including also the decay to Higgs bosons and another
scalar quark or to a top quark and the lightest neutralino. We find sizable
contributions to many partial decay widths and branching ratios. They are
roughly of O(10%) of the tree-level results, but can go up to 30% or higher.
These contributions are important for the correct interpretation of scalar top
quark decays at the LHC and, if kinematically allowed, at the ILC. The
evaluation of the branching ratios of the heavy scalar top quark will be
implemented into the Fortran code FeynHiggs.Comment: 86 pages, 38 figures; minor changes, version published as Phys. Rev.
D86 (2012) 03501
New Particles Working Group Report of the Snowmass 2013 Community Summer Study
This report summarizes the work of the Energy Frontier New Physics working
group of the 2013 Community Summer Study (Snowmass)
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