A new method for simulating electroweak top-quark production processes is described along with its computer realization in the SingleTop event generator. Special attention is paid to the correct ...combination of events from two parts of the main t-channel production process: 2 → 2 with a b quark in the initial state and 2 → 3, where an additional b quark appears in the final state. Integration of these two contributions enables the generation of event samples including the first correction to the leading perturbation order, avoiding the double-counting problem and negative-weight events. The SingleTop generator is based on the complete set of the tree Feynman diagrams calculated by the CompHEP package.
The results of searches for effects beyond the Standard Model in processes of single top-quark production in the CMS experiment are presented. Anomalous contributions of the vector and magnetic types ...in top-quark interaction with the
W
boson and
b
quark and quark-flavor-changing neutral currents in top-quark interaction with the
c
or
u
quark via gluon exchange were studied. The respective analysis was performed with the aid of Bayesian neural networks. No statistically significant deviations were found, and upper limits on anomalous couplings at a 95% confidence level were set.
In this paper we report on LCG Monte-Carlo Data Base (MCDB) and software which has been developed to operate MCDB. The main purpose of the LCG MCDB project is to provide a storage and documentation ...system for sophisticated event samples simulated for the LHC Collaborations by experts. In many cases, the modern Monte-Carlo simulation of physical processes requires expert knowledge in Monte-Carlo generators or significant amount of CPU time to produce the events. MCDB is a knowledgebase mainly dedicated to accumulate simulated events of this type. The main motivation behind LCG MCDB is to make the sophisticated MC event samples available for various physical groups. All the data from MCDB is accessible in several convenient ways. LCG MCDB is being developed within the CERN LCG Application Area Simulation project.
Program title: LCG Monte-Carlo Data Base
Catalogue identifier: ADZX_v1_0
Program summary URL:
http://cpc.cs.qub.ac.uk/summaries/ADZX_v1_0.html
Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland
Licensing provisions: GNU General Public Licence
No. of lines in distributed program, including test data, etc.: 30 129
No. of bytes in distributed program, including test data, etc.: 216 943
Distribution format: tar.gz
Programming language: Perl
Computer: CPU: Intel Pentium 4, RAM: 1 Gb, HDD: 100 Gb
Operating system: Scientific Linux CERN 3/4
RAM: 1 073 741 824 bytes (1 Gb)
Classification: 9
External routines:
•
perl >= 5.8.5;
•
Perl modules
○
DBD-mysql >= 2.9004,
○
File::Basename,
○
GD::SecurityImage,
○
GD::SecurityImage::AC,
○
Linux::Statistics,
○
XML::LibXML > 1.6,
○
XML::SAX,
○
XML::NamespaceSupport;
•
Apache HTTP Server >= 2.0.59;
•
mod auth external >= 2.2.9;
•
edg-utils-system RPM package;
•
gd >= 2.0.28;
•
rpm package CASTOR-client >= 2.1.2-4;
•
arc-server (optional)
Nature of problem: Often, different groups of experimentalists prepare similar samples of particle collision events or turn to the same group of authors of Monte-Carlo (MC) generators to prepare the events. For example, the same MC samples of Standard Model (SM) processes can be employed for the investigations either in the SM analyses (as a signal) or in searches for new phenomena in Beyond Standard Model analyses (as a background). If the samples are made available publicly and equipped with corresponding and comprehensive documentation, it can speed up cross checks of the samples themselves and physical models applied. Some event samples require a lot of computing resources for preparation. So, a central storage of the samples prevents possible waste of researcher time and computing resources, which can be used to prepare the same events many times.
Solution method: Creation of a special knowledgebase (MCDB) designed to keep event samples for the LHC experimental and phenomenological community. The knowledgebase is realized as a separate web-server (
http://mcdb.cern.ch). All event samples are kept on types at CERN. Documentation describing the events is the main contents of MCDB. Users can browse the knowledgebase, read and comment articles (documentation), and download event samples. Authors can upload new event samples, create new articles, and edit own articles.
Restrictions: The software is adopted to solve the problems, described in the article and there are no any additional restrictions.
Unusual features: The software provides a framework to store and document large files with flexible authentication and authorization system. Different external storages with large capacity can be used to keep the files. The WEB Content Management System provides all of the necessary interfaces for the authors of the files, end-users and administrators.
Running time: Real time operations.
References:
1 The main LCG MCDB server,
http://mcdb.cern.ch/.
2 P. Bartalini, L. Dudko, A. Kryukov, I.V. Selyuzhenkov, A. Sherstnev, A. Vologdin, LCG Monte-Carlo data base,
hep-ph/0404241.
3 J.P. Baud, B. Couturier, C. Curran, J.D. Durand, E. Knezo, S. Occhetti, O. Barring, CASTOR: status and evolution, cs.oh/0305047.
Top Quark: Results and Prospects Boos, E.; Dudko, L.; Mandrik, P. ...
Physics of particles and nuclei,
05/2019, Volume:
50, Issue:
3
Journal Article
Peer reviewed
The basic concepts and current status of top-quark physics are reviewed. Basic properties and interactions of the top quark are described, and the main experimental results obtained at the Large ...Hadron Collider (LHC) are summarized. A perspective of top-quark physics at the LHC upon increasing its luminosity and/or collision energy are briefly reviewed. Possible manifestations of novel physics beyond the Standard Model in the top-quark sector are discussed.
Making the best choice of kinematic variables is one of the main steps in using Neural Networks (NN) in high-energy physics. Our optimizations are based on the analysis of the Feynman diagram ...structure (singularities and spin effects) for the signal and background processes. Applying this method leads to improved efficiency of the Higgs search compared with the earlier NN strategy and the conventional analysis.
The Letter is devoted to studies of prospects to search for hypothetical W′ gauge bosons at hadron colliders via single-top quark production process. A special attention is paid to the interference ...between the Standard Model (SM) W and W′ boson contributions. A model independent analysis is performed for a wide interval of W′ masses potentially acceptable for a detection at the Tevatron and LHC. It is shown that the interference contribution to the cross section of the most promising s-channel single-top production mode could be as large as 30% for certain parameter points which is comparable to NLO effects computed in previous studies separately for the W′ signal and the SM single-top background. The interference contribution affects particle distributions and has to be taken into account for more accurate W′ signal and background simulation.
We present a study of the normalized transverse momentum distribution of W bosons produced in p (p) over bar collisions, using data corresponding to an integrated luminosity of 4.35 fb(-1) collected ...with the D0 detector at the Fermilab Tevatron collider at root s = 1.96 TeV. The measurement focuses on the transverse momentum region below 15 GeV, which is of special interest for electroweak precision measurements; it relies on the same detector calibration methods which were used for the precision measurement of the W boson mass. The measured distribution is compared to different QCD predictions and a procedure is given to allow the comparison of any further theoretical models to the D0 data.
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