2,228 research outputs found
Comparison of Bayesian and particle swarm algorithms for hyperparameter optimisation in machine learning applications in high energy physics
When using machine learning (ML) techniques, users typically need to choose a
plethora of algorithm-specific parameters, referred to as hyperparameters. In
this paper, we compare the performance of two algorithms, particle swarm
optimisation (PSO) and Bayesian optimisation (BO), for the autonomous
determination of these hyperparameters in applications to different ML tasks
typical for the field of high energy physics (HEP). Our evaluation of the
performance includes a comparison of the capability of the PSO and BO
algorithms to make efficient use of the highly parallel computing resources
that are characteristic of contemporary HEP experiments.Comment: Accepted by Computer Physics Communications. Changes made compared to
previous version: added references to other strategies, added Zenodo entry
for the implemented software, added a brief description of PSO, added more
explanations regarding the benchmark task
Evolutionary algorithms for hyperparameter optimization in machine learning for application in high energy physics
The analysis of vast amounts of data constitutes a major challenge in modern
high energy physics experiments. Machine learning (ML) methods, typically
trained on simulated data, are often employed to facilitate this task. Several
choices need to be made by the user when training the ML algorithm. In addition
to deciding which ML algorithm to use and choosing suitable observables as
inputs, users typically need to choose among a plethora of algorithm-specific
parameters. We refer to parameters that need to be chosen by the user as
hyperparameters. These are to be distinguished from parameters that the ML
algorithm learns autonomously during the training, without intervention by the
user. The choice of hyperparameters is conventionally done manually by the user
and often has a significant impact on the performance of the ML algorithm. In
this paper, we explore two evolutionary algorithms: particle swarm optimization
(PSO) and genetic algorithm (GA), for the purposes of performing the choice of
optimal hyperparameter values in an autonomous manner. Both of these algorithms
will be tested on different datasets and compared to alternative methods.Comment: Corrected typos. Removed a remark on page 2 regarding the similarity
of minimization and maximization problem. Removed a remark on page 9
(Summary) regarding thee ANN, since this was not studied in the pape
Forward pi^0 Production and Associated Transverse Energy Flow in Deep-Inelastic Scattering at HERA
Deep-inelastic positron-proton interactions at low values of Bjorken-x down
to x \approx 4.10^-5 which give rise to high transverse momentum pi^0 mesons
are studied with the H1 experiment at HERA. The inclusive cross section for
pi^0 mesons produced at small angles with respect to the proton remnant (the
forward region) is presented as a function of the transverse momentum and
energy of the pi^0 and of the four-momentum transfer Q^2 and Bjorken-x.
Measurements are also presented of the transverse energy flow in events
containing a forward pi^0 meson. Hadronic final state calculations based on QCD
models implementing different parton evolution schemes are confronted with the
data.Comment: 27 pages, 8 figures and 3 table
Validation of the revised IPSS at transplant in patients with myelodysplastic syndrome/transformed acute myelogenous leukemia receiving allogeneic stem cell transplantation
The International Prognostic Scoring System has been revised (IPSS-R) to predict prognosis of patients with myelodysplastic syndromes at diagnosis. To validate the use of the IPSS-R assesse
Performance of the CMS Cathode Strip Chambers with Cosmic Rays
The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device
in the CMS endcaps. Their performance has been evaluated using data taken
during a cosmic ray run in fall 2008. Measured noise levels are low, with the
number of noisy channels well below 1%. Coordinate resolution was measured for
all types of chambers, and fall in the range 47 microns to 243 microns. The
efficiencies for local charged track triggers, for hit and for segments
reconstruction were measured, and are above 99%. The timing resolution per
layer is approximately 5 ns
IGLV3-21*01 is an inherited risk factor for CLL through the acquisition of a single-point mutation enabling autonomous BCR signaling
The prognosis of chronic lymphocytic leukemia (CLL) depends on different markers, including cytogenetic aberrations, oncogenic mutations, and mutational status of the immunoglobulin (Ig) heavy-chain variable (IGHV) gene. The number of IGHV mutations distinguishes mutated (M) CLL with a markedly superior prognosis from unmutated (UM) CLL cases. In addition, B cell antigen receptor (BCR) stereotypes as defined by IGHV usage and complementarity-determining regions (CDRs) classify ∼30% of CLL cases into prognostically important subsets. Subset 2 expresses a BCR with the combination of IGHV3-21-derived heavy chains (HCs) with IGLV3-21-derived light chains (LCs), and is associated with an unfavorable prognosis. Importantly, the subset 2 LC carries a single-point mutation, termed R110, at the junction between the variable and constant LC regions. By analyzing 4 independent clinical cohorts through BCR sequencing and by immunophenotyping with antibodies specifically recognizing wild-type IGLV3-21 and R110-mutated IGLV3-21 (IGLV3-21R110), we show that IGLV3-21R110-expressing CLL represents a distinct subset with poor prognosis independent of IGHV mutations. Compared with other alleles, only IGLV3-21*01 facilitates effective homotypic BCR-BCR interaction that results in autonomous, oncogenic BCR signaling after acquiring R110 as a single-point mutation. Presumably, this mutation acts as a standalone driver that transforms IGLV3-21*01-expressing B cells to develop CLL. Thus, we propose to expand the conventional definition of CLL subset 2 to subset 2L by including all IGLV3-21R110-expressing CLL cases regardless of IGHV mutational status. Moreover, the generation of monoclonal antibodies recognizing IGLV3-21 or mutated IGLV3-21R110 facilitates the recognition of B cells carrying this mutation in CLL patients or healthy donors
Performance and Operation of the CMS Electromagnetic Calorimeter
The operation and general performance of the CMS electromagnetic calorimeter
using cosmic-ray muons are described. These muons were recorded after the
closure of the CMS detector in late 2008. The calorimeter is made of lead
tungstate crystals and the overall status of the 75848 channels corresponding
to the barrel and endcap detectors is reported. The stability of crucial
operational parameters, such as high voltage, temperature and electronic noise,
is summarised and the performance of the light monitoring system is presented
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