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Author: Patricia Burchat
Publisher: Ann Arbor, Mich. : University Microfilms International
ISBN:
Category : Leptons (Nuclear physics)
Languages : en
Pages : 292
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Book Description
Author: Patricia Burchat
Publisher: Ann Arbor, Mich. : University Microfilms International
ISBN:
Category : Leptons (Nuclear physics)
Languages : en
Pages : 292
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Previous measurements of the branching fractions of the tau lepton result in a discrepancy between the inclusive branching fraction and the sum of the exclusive branching fractions to final states containing one charged particle. The sum of the exclusive branching fractions is significantly smaller than the inclusive branching fraction. In this analysis, the branching fractions for all the major decay modes are measured simultaneously with the sum of the branching fractions constrained to be one. The branching fractions are measured using an unbiased sample of tau decays, with little background, selected from 207 pb−1 of data accumulated with the Mark II detector at the PEP ee− storage ring. The sample is selected using the decay products of one member of the .gamma.gamma.− pair produced in e+e− annihilation to identify the event and then including the opposite member of the pair in the sample. The sample is divided into subgroups according to charged and neutral particle multiplicity, and charged particle identification. The branching fractions are simultaneously measured using an unfold technique and a maximum likelihood fit. The results of this analysis indicate that the discrepancy found in previous experiments is possibly due to two sources. First, the leptonic branching fractions measured in this analysis are about one standard deviation higher than the world average. The measured leptonic branching fractions correspond to a tau lifetime of (3.0 +- 0.2) x 10−13 s. Secondly, the total branching fraction to one charged hadron plus at least one neutral particle is measured to be (7 +- 3)% higher than the branching fraction expected from a combination of previous measurements and theoretical predictions. It is shown that decay modes involving the eta are not expected to contribute more than 3% to this excess.
Author: Andrzej J. Buras
Publisher: Cambridge University Press
ISBN: 1107034035
Category : Science
Languages : en
Pages : 739
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Book Description
"The ultimate question of elementary particle physics is: What is the fundamental Lagrangian of nature surrounding us? The Lagrangian of the SM is very successful in describing nature at the currently available energy range. The discovery of the Higgs boson completed the particle spectrum of the SM and it is another proof of how well the SM works. Nevertheless the SM cannot be the end of the story and it is for sure not the fundamental Lagrangian of nature. The Lagrangian of the SM looses its validity at the latest at the Planck scale where gravitational effects become noticeable.Most physicists think of the SM as an effective theory that has to be replaced by a more fundamental theory above the TeV scale. What the word effective really means will hopefully be clear at later stages of our book. For the time being we will list some problems and open questions of the SM"--
Author: D Page
Publisher: World Scientific
ISBN: 9814549851
Category :
Languages : en
Pages : 570
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Book Description
This volume explores the recent trends in particle physics and cosmology. The invited lecturers include D Caldwell, A Linde, A B MacDonald, J Peebles, K Rolfs and D Schramm.
Author: Eugene Kennedy
Publisher: BoD – Books on Demand
ISBN: 9535104810
Category : Science
Languages : en
Pages : 126
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Book Description
Stimulated by the Large Hadron Collider and the search for the elusive Higgs Boson, interest in particle physics continues at a high level among scientists and the general public. This book includes theoretical aspects, with chapters outlining the generation model and a charged Higgs boson model as alternative scenarios to the Standard Model. An introduction is provided to postulated axion photon interactions and associated photon dispersion in magnetized media. The complexity of particle physics research requiring the synergistic combination of theory, hardware and computation is described in terms of the e-science paradigm. The book concludes with a chapter tackling potential radiation hazards associated with extremely weakly interacting neutrinos if produced in copious amounts with future high-energy muon-collider facilities.
Author: Glenn Cunningham
Publisher: Scientific e-Resources
ISBN: 1839473851
Category :
Languages : en
Pages : 316
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Book Description
Particle physics (also high energy physics) is the branch of physics that studies the nature of the particles that constitute matter and radiation. Although the word "e;particle"e; can refer to various types of very small objects "e;particle physics"e; usually investigates the irreducibly smallest detectable particles and the fundamental interactions necessary to explain their behaviour. By our current understanding, these elementary particles are excitations of the quantum fields that also govern their interactions. The currently dominant theory explaining these fundamental particles and fields, along with their dynamics, is called the Standard Model. Thus, modern particle physics generally investigates the Standard Model and its various possible extensions, e.g. to the newest "e;known"e; particle, the Higgs boson, or even to the oldest known force field, gravity. Written in a clear pedagogic style by active researchers, this book will prepare a beginner to work in the field and at the same time will also provide useful reference material for active researchers.
Author: K Huitu
Publisher: CRC Press
ISBN: 9780750306614
Category : Science
Languages : en
Pages : 1112
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Book Description
High Energy Physics 99 contains the 18 invited plenary presentations and 250 contributions to parallel sessions presented at the International Europhysics Conference on High Energy Physics. The book provides a comprehensive survey of the latest developments in high energy physics. Topics discussed include hard high energy, structure functions, soft interactions, heavy flavor, the standard model, hadron spectroscopy, neutrino masses, particle astrophysics, field theory, and detector development.
Author: Cecilia Tosciri
Publisher: Springer Nature
ISBN: 3030879380
Category : Science
Languages : en
Pages : 171
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Book Description
The discovery in 2012 of the Higgs boson at the Large Hadron Collider (LHC) represents a milestone for the Standard Model (SM) of particle physics. Most of the SM Higgs production and decay rates have been measured at the LHC with increased precision. However, despite its experimental success, the SM is known to be only an effective manifestation of a more fundamental description of nature. The scientific research at the LHC is strongly focused on extending the SM by searching, directly or indirectly, for indications of New Physics. The extensive physics program requires increasingly advanced computational and algorithmic techniques. In the last decades, Machine Learning (ML) methods have made a prominent appearance in the field of particle physics, and promise to address many challenges faced by the LHC. This thesis presents the analysis that led to the observation of the SM Higgs boson decay into pairs of bottom quarks. The analysis exploits the production of a Higgs boson associated with a vector boson whose signatures enable efficient triggering and powerful background reduction. The main strategy to maximise the signal sensitivity is based on a multivariate approach. The analysis is performed on a dataset corresponding to a luminosity of 79.8/fb collected by the ATLAS experiment during Run-2 at a centre-of-mass energy of 13 TeV. An excess of events over the expected background is found with an observed (expected) significance of 4.9 (4.3) standard deviation. A combination with results from other \Hbb searches provides an observed (expected) significance of 5.4 (5.5). The corresponding ratio between the signal yield and the SM expectation is 1.01 +- 0.12 (stat.)+ 0.16-0.15(syst.). The 'observation' analysis was further extended to provide a finer interpretation of the V H(H → bb) signal measurement. The cross sections for the VH production times the H → bb branching ratio have been measured in exclusive regions of phase space. These measurements are used to search for possible deviations from the SM with an effective field theory approach, based on anomalous couplings of the Higgs boson. The results of the cross-section measurements, as well as the constraining of the operators that affect the couplings of the Higgs boson to the vector boson and the bottom quarks, have been documented and discussed in this thesis. This thesis also describes a novel technique for the fast simulation of the forward calorimeter response, based on similarity search methods. Such techniques constitute a branch of ML and include clustering and indexing methods that enable quick and efficient searches for vectors similar to each other. The new simulation approach provides optimal results in terms of detector resolution response and reduces the computational requirements of a standard particles simulation.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The structure of the weak hadronic current coupled to the tau is investigated via some of the hadronic decays of the tau. The vector current coupling is determined by measuring the tau .-->. rho .nu./sub tau/ branching ratio. The axial-vector coupling is determined by measuring the tau .-->. .pi. .nu./sub tau/ branching ratio. The Cabibbo structure of the hadronic current is established by observing the decay tau .-->. K*(890).nu./sub tau/ and measuring its branching ratio. The branching ratios for the decays tau .-->. e anti .nu./sub e/.nu./sub tau/ and tau .-->. .mu. anti .nu./sub .mu./.nu./sub tau/ are measured as a normalization for the hadronic decays and as a check on the validity of the measurements. The leptonic branching ratios agree well with previous experiments. From a kinematic fit to the pion energy spectrum in the decay tau .-->. .pi. .nu./sub tau/, an upper limit (95% confidence level) of 245 MeV is placed on the tau neutrino mass. From a simultaneous fit of the center of mass energy dependence of the tau production cross section and the pion energy spectrum in the decay tau .-->. .pi. .nu./sub tau/, the tau mass is determined to be 1.787 +- 010 GeV/c. All properties of the tau measured here are consistent with it being a sequential lepton coupled to the ordinary weak hadronic current.
Author: Mario Campanelli
Publisher: Springer Science & Business Media
ISBN: 3540328416
Category : Science
Languages : en
Pages : 360
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Book Description
This book gathers the proceedings of The Hadron Collider Physics Symposia (HCP) 2005, and reviews the state-of-the-art in the key physics directions of experimental hadron collider research. Topics include QCD physics, precision electroweak physics, c-, b-, and t-quark physics, physics beyond the Standard Model, and heavy ion physics. The present volume serves as a reference for everyone working in the field of accelerator-based high-energy physics.
