Higgs Boson Decays Into a Pair of Bottom Quarks PDF Download

Author: Cecilia Tosciri
Publisher:
ISBN: 9783030879396
Category :
Languages : en
Pages : 0

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Book Description
This thesis presents the analysis that led to the observation of the Standard Model (SM) Higgs boson decay into pairs of bottom quarks. The analysis, based on a multivariate strategy, exploits the production of a Higgs boson associated with a vector boson. The analysis was 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 observed in a combination with complementary Hbb searches. The analysis was extended to provide a finer interpretation of the signal measurement. The cross sections of the V H(H → bb) process have been measured in exclusive regions of phase space and used to search for deviations from the SM with an effective field theory approach. The results are discussed in this book. A novel technique for the fast simulation of the ATLAS forward calorimeter response is also presented. The new technique is based on similarity search, a branch of machine learning that enables quick and efficient searches for vectors similar to each other.

Author: Yangyang Cheng
Publisher: Springer
ISBN: 331944218X
Category : Science
Languages : en
Pages : 176

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Book Description
This thesis reports on the search for dark matter in data taken with the ATLAS detector at CERN’s Large Hadron Collider (LHC). The identification of dark matter and the determination of its properties are among the highest priorities in elementary particle physics and cosmology. The most likely candidate, a weakly interacting massive particle, could be produced in the high energy proton-proton collisions at the LHC. The analysis presented here is unique in looking for dark matter produced together with a Higgs boson that decays into its dominant decay mode, a pair of b quarks. If dark matter were seen in this mode, we would learn directly about the production mechanism because of the presence of the Higgs boson. This thesis develops the search technique and presents the most stringent production limit to date.

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: Don Lincoln
Publisher: JHU Press
ISBN: 1421413515
Category : Science
Languages : en
Pages : 238

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Book Description
Lincoln, a senior scientist at Fermi National Accelerator Laboratory and adjunct professor of physics at Notre Dame, gives readers an insider's view of the Hadron Collider from its conception, through its early discoveries and difficulties, to its greatest triumph, the discovery of the Higgs boson.

Author: Marcel Rieger
Publisher: Springer Nature
ISBN: 3030653803
Category : Science
Languages : en
Pages : 217

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Book Description
In 1964, a mechanism explaining the origin of particle masses was proposed by Robert Brout, François Englert, and Peter W. Higgs. 48 years later, in 2012, the so-called Higgs boson was discovered in proton-proton collisions recorded by experiments at the LHC. Since then, its ability to interact with quarks remained experimentally unconfirmed. This book presents a search for Higgs bosons produced in association with top quarks tt̄H in data recorded with the CMS detector in 2016. It focuses on Higgs boson decays into bottom quarks H → bb̅ and top quark pair decays involving at least one lepton. In this analysis, a multiclass classification approach using deep learning techniques was applied for the first time. In light of the dominant background contribution from tt̄ production, the developed method proved to achieve superior sensitivity with respect to existing techniques. In combination with searches in different decay channels, the presented work contributed to the first observations of tt̄H production and H → bb̅ decays.

Author: Don Lincoln
Publisher: JHU Press
ISBN: 0801896444
Category : Science
Languages : en
Pages : 190

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Book Description
The highest-energy particle accelerator ever built, the Large Hadron Collider runs under the border between France and Switzerland. It leapt into action on September 10, 2008, amid unprecedented global press coverage and widespread fears that its energy would create tiny black holes that could destroy the earth. By smashing together particles smaller than atoms, the LHC recreates the conditions hypothesized to have existed just moments after the big bang. Physicists expect it to aid our understanding of how the universe came into being and to show us much about the standard model of particle physics—even possibly proving the existence of the mysterious Higgs boson. In exploring what the collider does and what it might find, Don Lincoln explains what the LHC is likely to teach us about particle physics, including uncovering the nature of dark matter, finding micro black holes and supersymmetric particles, identifying extra dimensions, and revealing the origin of mass in the universe. Thousands of physicists from around the globe will have access to the LHC, none of whom really knows what outcomes will be produced by the $7.7 billion project. Whatever it reveals, the results arising from the Large Hadron Collider will profoundly alter our understanding of the cosmos and the atom and stimulate amateur and professional scientists for years to come.

Author: Leon M. Lederman
Publisher: Houghton Mifflin Harcourt
ISBN: 9780618711680
Category : Science
Languages : en
Pages : 452

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Book Description
A fascinating tour of particle physics from Nobel Prize winner Leon Lederman. At the root of particle physics is an invincible sense of curiosity. Leon Lederman embraces this spirit of inquiry as he moves from the Greeks' earliest scientific observations to Einstein and beyond to chart this unique arm of scientific study. His survey concludes with the Higgs boson, nicknamed the God Particle, which scientists hypothesize will help unlock the last secrets of the subatomic universe, quarks and all--it's the dogged pursuit of this almost mystical entity that inspires Lederman's witty and accessible history.

Author: Maria Mironova
Publisher: Springer Nature
ISBN: 3031362209
Category : Science
Languages : en
Pages : 206

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Book Description
This book explores the Higgs boson and its interactions with fermions, as well as the detector technologies used to measure it. The Standard Model of Particle Physics has been a groundbreaking theory in our understanding of the fundamental properties of the universe, but it is incomplete, and there are significant hints which require new physics. The discovery of the Higgs boson in 2012 was a substantial confirmation of the Standard Model, but many of its decay modes remain elusive. This book presents the latest search for Higgs boson decays into c-quarks using a proton-proton collision dataset collected by the ATLAS experiment at the Large Hadron Collider (LHC). This decay mode has yet to be observed and requires advanced machine learning algorithms to identify c-quarks in the experiment. The results provide an upper limit on the rate of Higgs boson decays to c-quarks and a direct measurement of the Higgs boson coupling strength to c-quarks. The book also discusses the future of particle physics and the need for significant improvements to the detector to cope with increased radiation damage and higher data rates at the High-Luminosity LHC. It presents the characterization of the ATLAS pixel detector readout chip for the inner detector upgrade (ITk). The chip was subjected to irradiations using X-rays and protons to simulate the radiation environment at the HL-LHC. The tests showed that all readout chip components, including the digital logic and analogue front-end, are sufficiently radiation-tolerant to withstand the expected radiation dose. Finally, this book describes monolithic pixel detectors as a possible technology for future pixel detectors. This book is ideal for individuals interested in exploring particle physics, the Higgs boson, and the development of silicon pixel detectors.

Author: Don Lincoln
Publisher: World Scientific
ISBN: 9814458058
Category : Science
Languages : en
Pages : 596

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Book Description
The Big Bang, the birth of the universe, was a singular event. All of the matter of the universe was concentrated at a single point, with temperatures so high that even the familiar protons and neutrons of atoms did not yet exist, but rather were replaced by a swirling maelstrom of energy, matter and antimatter. Exotic quarks and leptons flickered briefly into existence, before merging back into the energy sea. This book explains the fascinating world of quarks and leptons and the forces that govern their behavior. Told from an experimental physicist's perspective, it forgoes mathematical complexity, using instead particularly accessible figures and apt analogies. In addition to the story of quarks and leptons, which are regarded as well-accepted fact, the author (who is a leading researcher at one of the world's highest energy particle physics laboratories) also discusses mysteries at both the experimental and theoretical frontiers, before tying it all together with the exciting field of cosmology and indeed the birth of the universe itself. The text spans the tiny world of the quark to the depths of the universe with breathtaking clarity. The casual student of science will appreciate the careful distinction between what is known (quarks, leptons and antimatter), what is suspected (Higgs bosons, neutrino oscillations and the reason why the universe has so little antimatter) and what is merely dreamed (supersymmetry, superstrings and extra dimensions). Included is an unprecedented chapter explaining the accelerators and detectors of modern particle physics experiments. The chapter discussing the hunt for the Higgs boson — currently consuming the efforts of nearly 6000 physicists — reveals drama that only big-stakes science can give. Understanding the Universe leaves the reader with a deep appreciation of the fascinating particle realm and reverence for just how much it determines the rich beauty of our universe. Since the release of the first edition, the landscape has changed. The venerable Fermilab Tevatron has ceased operations after a quarter century of extraordinary performance, to be replaced by the CERN Large Hadron Collider, an accelerator with a design energy of seven times greater than the Tevatron and a collision rate of nearly a billion collisions per second. The next few years promise to be very exciting as scientists explore this new realm. This revised edition of Understanding the Universe will leave the reader with a deep appreciation of just why physicists are so excited. Contents:Early HistoryThe Path to Knowledge (History of Particle Physics)Quarks and LeptonsForces: What Holds It All TogetherHunting for the HiggsAccelerators and Detectors: Tools of the TradeNear Term MysteriesExotic Physics (The Next Frontier)Recreating the Universe 10,000,000 Times a SecondEpilogue: Why Do We Do It? Readership: Students, scientists and lay people. Keywords:Quarks;Leptons;Accelerators;UniverseReviews: “Lincoln has an infectious love for physics … (and) demonstrates a humorous writing style that successfully engages the reader.” Publishers Weekly “The author is well equipped to write a book on the topic … It is not light reading, but worth the effort … Lincoln is careful to distinguish between what is known versus what is merely dreamed.” Mensa Bulletin “A veteran of many popular talks on physics, (Lincoln) charmingly relates the tale of humankind's almost insatiable curiosity about the ultimate nature of nature and the quest to determine the basic particles of matter. His style is engaging and obviously directed to informed lay readers, but the more scientifically minded will find it equally appealing … If digested with the notion that this topic is presented in a broad swath, both historically and scientifically, and not meant to be definitive, the work offers readers an appreciation of the investigative procedure, the accumulated body of research, and the people who did the investigating.” Library Journal “Don Lincoln, an experimentalist on DZero at Fermilab, motivates his tale of the development of particle physics, from its origins to its current state, almost entirely by experiments, a refreshing alternative to the usual theoretical treatments. Rather than posing thought experiments, Lincoln describes real experiments that have led to deeper questions and the consequent progress of particle physics … With his light and easy-to-read style, Lincoln's humor and personal tales do much to convey the flavor of modern particle physics research — a picture that is not often painted so realistically in other popular physics books. The content is more complicated than in most similar books, but this is a virtue for its intended audience, as it allows for greater depth.” Symmetry “Knowledgeably written … ‘Understanding the Universe’ provides the nonspecialist general reader with a fascinating and informative introduction to the complex world of quarks, leptons, and the forces that govern particle physics. Written especially to introduce lay readers to subatomic mysteries, (the book) discusses the Big Bang, known and proven theories, suspected hypotheses that have yet to be firmly established, cutting-edge discussions of modern particle physics experiments, and much more. Black-and-white diagrams help illustrate the amazing ideas presented with a minimum of mathematics and a maximum of awe.” Midwest Book Review “Don Lincoln takes us on a rollicking tour of the universe: The reader finds out what we particle physicists understand about it, how we arrived at that understanding and where we think we're going next with our research … Lincoln enlivens the landscape with fresh details, irreverent (yet never unkind) remarks on the cast of characters, and explanations that are homey, humorous and often completely original … In his epilogue Lincoln addresses explicitly the question of why particle physicists ask why … the real reason we do research is simply this: It's tremendously fun to figure the universe out.” American Scientist “… Lincoln offers lay readers a complete tour of particle physics …(he) writes very well, using a mixture of humor, history and analogies as well basic scientific explanations … (and) does a particularly good job of covering the full gamut of particle physics.” Choice “This book is addressed to the curious layman, with only a murky recollection of school physics, who wants to know how far mankind has gone in understanding the world around us … It is an excellent reference for any scientist who is occasionally unsure how best to explain a particular physics concept to a non-specialist audience … his understanding and explanations of complex phenomena are excellent and the book strikes a balance between depth and accessibility.” CERN Courier “The author faces complex topics in a very simple and clever way without using mathematics but by simple (and suitable) analogies. The reading is intriguing and very flowing and, sometimes, very entertaining. The book is peppered with amusing anecdotes that make reading smoother and funny. This book is a masterpiece of scientific disclosure. I recommend its reading for those people who want to delve into the wonders of modern Physics.” Zentralblatt MATH

Author: Cecilia Tosciri
Publisher: Springer
ISBN: 9783030879402
Category : Science
Languages : en
Pages : 0

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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.