Search for New Phenomena in Top-Antitop Quarks Final States with Additional Heavy-Flavour Jets with the ATLAS Detector
Search for New Phenomena in Top-Antitop Quarks Final States with Additional Heavy-Flavour Jets with the ATLAS Detector

Author: Daiki Yamaguchi

Publisher: Springer Nature

Published: 2019-10-30

Total Pages: 279

ISBN-13: 9811509328

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This book reports on the search for a new heavy particle, the Vector-Like Top quark (VLT), in the Large Hadron Collider (LHC) at CERN. The signal process is the pair production of VLT decaying into a Higgs boson and top quark (TT→Ht+X, X=Ht, Wb, Zt). The signal events result in top–antitop quarks final states with additional heavy flavour jets. The book summarises the analysis of the data collected with the ATLAS detector in 2015 and 2016. In order to better differentiate between signals and backgrounds, exclusive taggers of top quark and Higgs boson were developed and optimised for VLT signals. These efforts improved the sensitivity by roughly 30%, compared to the previous analysis. The analysis outcomes yield the strongest constraints on parameter space in various BSM theoretical models. In addition, the book addresses detector operation and the evaluation of tracking performance. These efforts are essential to properly collecting dense events and improving the accuracy of the reconstructed objects that are used for particle identification. As such, they represent a valuable contribution to data analysis in extremely dense environments.

Recent Results from the Search for New Phenomena at
Recent Results from the Search for New Phenomena at

Author:

Publisher:

Published: 1997

Total Pages: 17

ISBN-13:

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We present results from several new searches for physics beyond the Standard Model. We describe a search based on the scalar sum of the transverse energy of the event, a global quantity nearly independent of the event topology. We summarize our searches for first generation leptoquarks into all three decay channels, eq{ovr eq}, eq{ovr?q}, and {nu}q{ovr {nu}q} and note that this is the first time that the triumvirate of decay channels has been searched. We do not find any evidence for production of first generation leptoquarks and set a lower limit on the mass of the leptoquark of 175 GeV/c2, assuming the decay is exclusively into eq{ovr eq}. We also present results from the first search for a third generation leptoquark with charge ±1/3. Again, we find no evidence for its existence for a mass less than 80 GeV/c2 Finally, we discuss one of our searches for supersymmetry, specifically the pair-production of {tilde e}, {tilde {nu}}, and {tilde {chi}}°2 where the decay yields final states with two photons plus missing transverse energy (E{sub T}). We set limits on the production cross section ranging from 1 pb to 400 fb, depending on the mass. This analysis also sets a model-independent limit of? · B(pp -?? {vert_bar} E{sub T} {vert_bar} X) 185 fb at the 95% CL for E{sub T}{sup ({gamma})} 12 GeV and {vert_bar}?{vert_bar} 1.1 T and E{sub T} 25 GeV.

Search for New Phenomena in Dijet Angular Distributions at √s = 8 and 13 TeV
Search for New Phenomena in Dijet Angular Distributions at √s = 8 and 13 TeV

Author: Lene Kristian Bryngemark

Publisher: Springer

Published: 2017-12-29

Total Pages: 177

ISBN-13: 3319673467

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This thesis describes the use of the angular distributions of the most energetic dijets in data recorded by the ATLAS experiment, at CERN’s Large Hadron Collider (LHC), the goal of which is to search for phenomena beyond what the current theory of Particle Physics (the Standard Model) can describe. It also describes the deployment of the method used in ATLAS to correct for the distortions in jet energy measurements caused by additional proton–proton interactions. The thesis provides a detailed introduction to understanding jets and dijet searches at the LHC. The experiments were carried out at two record collider centre-of-mass energies (8 and 13 TeV), probing smaller distances than ever before. Across a broad momentum transfer range, the proton constituents (quarks and gluons) display the same kinematical behaviour, and thus still appear to be point-like. Data are compared to predictions corrected for next-to-leading order quantum chromodynamics (NLO QCD) as well as electroweak effects, demonstrating excellent agreement. The results are subsequently used to set limits on parameters of suggested theoretical extensions to the Standard Model (SM), including the effective coupling and mass of a Dark Matter mediator.

Search for New Phenomena in Events with a Photon and Missing Transverse Momentum in [math Display
Search for New Phenomena in Events with a Photon and Missing Transverse Momentum in [math Display

Author:

Publisher:

Published: 2015

Total Pages:

ISBN-13:

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Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum with the ATLAS experiment at the LHC are reported. Data were collected in proton-proton collisions at a center-of-mass energy of 8 TeV and correspond to an integrated luminosity of 20.3 fb-1. The observed data are well described by the expected Standard Model backgrounds. The expected (observed) upper limit on the fiducial cross section for the production of events with a photon and large missing transverse momentum is 6.1 (5.3) fb at 95% confidence level. The exclusion limits are presented on models of new phenomena with large extra spatial dimensions, supersymmetric quarks, and direct pair production of dark-matter candidates.

Search for New Phenomena in Final States with an Energetic Jet and Large Missing Transverse Momentum in Pp Collisions at \(\sqrt{s{\mathrm{}}}
Search for New Phenomena in Final States with an Energetic Jet and Large Missing Transverse Momentum in Pp Collisions at \(\sqrt{s{\mathrm{}}}

Author:

Publisher:

Published: 2015

Total Pages:

ISBN-13:

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Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb-1 of \(\sqrt{s{\mathrm{}}} = 8\) TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT>120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between EmissT>150 GeV and EmissT>700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. Limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presented.

New Phenomena And New States Of Matter In The Universe: From Quarks To Cosmos
New Phenomena And New States Of Matter In The Universe: From Quarks To Cosmos

Author: Cesar Augusto Zen Vasconcellos

Publisher: World Scientific

Published: 2023-01-17

Total Pages: 375

ISBN-13: 9811220921

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Recent discoveries in astronomy and relativistic astrophysics as well as experiments on particle and nuclear physics have blurred the traditional boundaries of physics. It is believed that at the birth of the Universe, a whirlwind of matter and antimatter, of quarks and exotic leptons, briefly appeared and merged into a sea of energy. The new phenomena and new states of matter in the Universe revealed the deep connection between quarks and the Cosmos. Motivated by these themes, this book discusses different topics: gravitational waves, dark matter, dark energy, exotic contents of compact stars, high-energy and gamma-ray astrophysics, heavy ion collisions and the formation of the quark-gluon plasma in the early Universe. The book presents some of the latest researches on these fascinating themes and is useful for experts and students in the field.

Anomaly! Collider Physics And The Quest For New Phenomena At Fermilab
Anomaly! Collider Physics And The Quest For New Phenomena At Fermilab

Author: Tommaso Dorigo

Publisher: World Scientific

Published: 2016-09-26

Total Pages: 304

ISBN-13: 1786341131

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'Dorigo provides an engaging and insightful perspective on the pursuit of physics discoveries at CDF … Dorigo’s book is thus almost certainly going to be an important source for anyone interested in the history of CDF … It is a personal yet highly informative story of discovery and almost-discovery from the perspective of someone who saw the events firsthand.'Physics TodayFrom the mid-1980s, an international collaboration of 600 physicists embarked on the investigation of subnuclear physics at the high-energy frontier. As well as discovering the top quark, the heaviest elementary particle ever observed, the physicists analyzed their data to seek signals of new physics which could revolutionize our understanding of nature.Anomaly! tells the story of that quest, and focuses specifically on the finding of several unexplained effects which were unearthed in the process. These anomalies proved highly controversial within the large team: to some collaborators they called for immediate publication, while to others their divulgation threatened to jeopardize the reputation of the experiment.Written in a confidential, narrative style, this book looks at the sociology of a large scientific collaboration, providing insight in the relationships between top physicists at the turn of the millennium. The stories offer an insider's view of the life cycle of the 'failed' discoveries that unavoidably accompany even the greatest endeavors in modern particle physics.

Search for New Phenomena in Events with at Least Three Photons Collected in Pp Collisions at {u221A}s
Search for New Phenomena in Events with at Least Three Photons Collected in Pp Collisions at {u221A}s

Author:

Publisher:

Published: 2016

Total Pages: 26

ISBN-13:

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Results of a search for new phenomena in events with at least three photons are reported. Data from proton–proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb-1, were collected with the ATLAS detector at the LHC. The observed data are well described by the Standard Model. Limits at the 95 % confidence level on new phenomena are presented based on the rate of events in an inclusive signal region and a restricted signal region targeting the rare decay Z→3?, as well as di-photon and tri-photon resonance searches. For a Standard Model Higgs boson decaying to four photons via a pair of intermediate pseudoscalar particles (a), limits are found to be ???????? BR (h→aa)× BR (a→??)210sup-3/sup?SM for 10 GeV msuba/sub 62 GeV. Finally, limits are also presented for Higgs boson-like scalars (H) for m