Download or read book A Search for Supersymmetric Phenomena in Final States with High Jet Multiplicity at the ATLAS Detector written by Matthew N.K. Smith and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Constraints on the properties of reclustered large-radius jets are used to improve the sensitivity. The main Standard Model backgrounds are removed using a template method that extrapolates background behavior from final states with fewer jets. No excess is observed over prediction, so limits are set on supersymmetric particle masses in the context of two different theoretical models. Gluino masses below 1500 and 1600 GeV, respectively, are excluded, a significant extension of the limits set by previous analyses.

Download or read book Searches for Supersymmetric Particles in Final States with Multiple Top and Bottom Quarks with the Atlas Detector written by Chiara Rizzi and published by Springer Nature. This book was released on 2020-09-01 with total page 279 pages. Available in PDF, EPUB and Kindle. Book excerpt: This PhD thesis documents two of the highest-profile searches for supersymmetry performed at the ATLAS experiment using up to 80/fb of proton-proton collision data at a center-of-mass energy of 13 TeV delivered by the Large Hadron Collider (LHC) during its Run 2 (2015-2018). The signals of interest feature a high multiplicity of jets originating from the hadronisation of b-quarks and large missing transverse momentum, which constitutes one of the most promising final state signatures for discovery of new phenomena at the LHC. The first search is focused on the strong production of a pair of gluinos, with each gluino decaying into a neutralino and a top-antitop-quark pair or a bottom-antibottom-quark pair. The second search targets the pair production of higgsinos, with each higgsino decaying into a gravitino and a Higgs boson, which in turn is required to decay into a bottom-antibottom-quark pair. Both searches employ state-of-the-art experimental techniques and analysis strategies at the LHC, resulting in some of the most restrictive bounds available to date on the masses of the gluino,neutralino, and higgsino in the context of the models explored.

Download or read book Supersymmetric Beasts and Where to Find Them written by Marco Valente and published by Springer Nature. This book was released on 2022-03-05 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt: After an extensive overview of the Standard Model and of the theory and phenomenology of Supersymmetry, this book describes the recent development of the ATLAS Particle Flow algorithm, a hadronic reconstruction technique aiming at enhancing the sensitivity of the experiment to new physics through the combination of the information from different ATLAS sub-detectors. The first ever ATLAS strong SUSY search exploiting this technique is also described, reporting the results and exclusion limits obtained using the complete proton-proton collision dataset recorded by the ATLAS experiment during the second Run of the Large Hadron Collider (LHC).

Download or read book Search for Supersymmetric Particles in Final States with Leptons Jets and Missing Transverse Energy with the ATLAS Detector written by Peter Tornambè and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Supersymmetry (SUSY) is one of the most studied models to extend the Standard Model (SM) of Particle Physics beyond the electroweak scale. In many supersymmetric models, the lightest supersymmetric particle is stable and can be a suitable candidate for dark matter.\\ This dissertation summarises a search for supersymmetric phenomena produced via the strong or the electroweak interaction leading to final states with two leptons (electrons or muons) of the same electric charge, or three leptons, jets and missing transverse momentum. While the same-sign or three leptons signature is present in many SUSY scenarios, SM processes leading to such events have very small production rates. Therefore, this analysis benefits from a small SM background in the signal regions leading to a good sensitivity especially in SUSY scenarios with compressed mass spectra or in which the R-parity is not conserved. The search was performed with cut-and-count analyses exploiting the full dataset recorded with the ATLAS detector at the Large Hadron Collider during the years 2015 and 2016, corresponding to a total integrated luminosity of 36.1 fb$^{-1}$. No significant excess above the Standard Model expectations is observed. The results are interpreted in several simplified supersymmetric models featuring R-parity conservation or R-parity violation, extending the exclusion limits from previous searches.\\ Since no sign of SUSY particles has been observed, this dissertation presents prospects for a search for compressed electroweakino production. This supersymmetric scenario is particularly challenging for LHC experiments since the products of the decay chain have low energies and are therefore difficult to detect. Results are obtained with a parameterised simulation of the ATLAS detector performances at a centre-of-mass energy of 14 TeV and for an integrated luminosity of 3000 fb$^{-1}$.\\

Download or read book Search for Supersymmetry in Final States with Multiple Bottom Quarks with the ATLAS Detector written by Meisam Ghasemi Bostanabad and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The theoretical development of the Standard Model in the 1960s and 1970s has led to the discovery of its missing piece, the Higgs boson, at the ATLAS experiment (together with its sister experiment, CMS) at the Large Hadron Collider at CERN in 2012. In order to solve the problem of large quantum corrections to the leading expansion of the Higgs boson mass, additional symmetries need to be added to the Standard Model. A possible solution to this problem of Higgs mass quantum corrections is the theory of Supersymmetry, which includes partners to each Standard Model particle, such as gluinos, squarks, and the lightest supersymmetric particle. This dissertation describes a search for pair-produced gluinos, where each gluino decays via a top squark or a bottom squark to the lightest supersymmetric particle (a neutralino). Events which contain a large jet multiplicity in the final state (i.e. at least four jets of which at least three must be b-jets), and large amounts of missing transverse energy, are obtained for further studies. The dataset used for this search includes 139 fb^−1 of integrated luminosity recorded by the ATLAS experiment between 2015 and 2018 at a center-of-mass energy √s = 13 TeV. No significant excess is observed in data above the Standard Model backgrounds, and gluino masses up to 2.3 TeV for both the Gtt and the Gbb models are excluded at a 95% confidence level. This dissertation also contains an overview of, and the author's work on, the data quality monitoring of the ATLAS liquid argon calorimeter during 2017 data taking.

Download or read book High Jet Multiplicity Physics at the LHC written by Mireia Crispín Ortuzar and published by Springer. This book was released on 2016-08-25 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes research in two different areas of state-of-the-art hadron collider physics, both of which are of central importance in the field of particle physics. The first part of the book focuses on the search for supersymmetric particles called gluinos. The book subsequently presents a set of precision measurements of “multi-jet” collision events, which involve large numbers of newly created particles, and are among the dominant processes at the Large Hadron Collider (LHC). Now that a Higgs boson has been discovered at the LHC, the existence (or non-existence) of supersymmetric particles is of the utmost interest and significance, both theoretically and experimentally. In addition, multi-jet collision events are an important background process for a wide range of analyses, including searches for supersymmetry.

Download or read book What We Would Like Lhc To Give Us Proceedings Of The International School Of Subnuclear Physics written by Antonino Zichichi and published by World Scientific. This book was released on 2014-06-11 with total page 596 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is the proceedings of the International School of Subnuclear Physics, ISSP 2012, 50th Course — ERICE, 23 June 2013 - 2 July 2012. This course was devoted to the celebrations of the 50th Anniversary of the Subnuclear Physics School which was started in 1961 by Antonino Zichichi with John Bell at CERN and formally established in 1962 by Bell, Blackett, Weisskopf, Rabi and Zichichi in Geneva (CERN). The lectures covered the latest and most significant achievements in theoretical and in experimental subnuclear physics.

Download or read book Phenomena Beyond the Standard Model What Do We Expect for New Physics to Look Like written by Roman Pasechnik and published by Frontiers Media SA. This book was released on 2020-09-03 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact.

Download or read book Measuring the Standard Model and Searching for New Physics with Jet Substructure Using the ATLAS Detector written by Maximilian Swiatlowski and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Collisions at the Large Hadron Collider have offered an unprecedented window into some of the highest energy scales ever observed in experiments. Understanding these collisions, especially those that produce particles charged under quantum chromodynamics (QCD), requires a deep understanding of jets: the collimated sprays of particles produced by the parton shower and hadronization processes which emerge from the asymptotic freedom of QCD. Recent theoretical advances and the unprecedented capabilities of the ATLAS detector have enabled a new class of jet physics measurements based on the internal structure of jets, referred to as jet substructure. Three new types of measurements relying on jet substructure are presented. The first is a set of measurements sensitive which can discriminate between jets initiated by quarks and gluons. Separation is possible by studying variables sensitive to the magnitude of the color charge. Several such variables are measured, and a data-driven technique is used to construct a tagger, the first of its kind at a hadron collider, which can improve the sensitivity of searches for new physics in hadronic final states. A second measurement studies the color connections of jets in top-antitop events using an observable called the jet pull angle: sensitivity to the color representation of particles decaying to dijet pairs at a hadron collider is demonstrated for the first time. A final analysis searches for R-parity violating supersymmetry (SUSY) in all hadronic final states. These classes of models remove the characteristic missing energy signature which existing SUSY searches rely on, and require new discrimination techniques. Jet substructure provides a powerful handle to analyze these very high multiplicity states using a variable called the total jet mass. No signal is observed over the Standard Model (SM) prediction, and new limits are set on these previously unexplored models. The techniques of jet substructure lie at the hearts of all of these analyses, enabling both new measurements of SM phenomena and entirely new searches for physics beyond the SM.

Download or read book Search for Supersymmetry in Dijet and Multijet Channels and Soft QCD Measurements Using the ATLAS Detector at the Large Hadron Collider written by Rishiraj Pravahan and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The ATLAS experiment at the CERN Large Hadron Collider (LHC) has collected a substantial amount of data to understand the Standard Model of particle physics at higher than previous center of mass energy available and to explore new physics beyond the Standard Model. This dissertation describes observations of charged particle multiplicity distributions in 7 TeV and 900 GeV data as well as searches for new physics with a signature of high energy jets and missing transverse energy using the first few months of data available at the LHC. Multiplicity distributions of charged particle tracks, one of the first observables in high energy collisions were made for a center of mass energy, sqrt (s) = 900 GeV as well as 7 TeV proton-proton collision data. Such distributions help to understand multi-particle production processes. One of the predicted features of multiplicity distribution and its moments is KNO scaling which implies that the shape and moments of the scaled multiplicity distribution is independent of the center-of-mass energy. Although a clear violation of KNO scaling is not observed within the error limits, an indication of such violation is noted. Different models of hadro-production to describe multiplicity distributions are also studied. The Negative Binomial Distribution (NBD) is an often used distribution modeling multiplicity distributions. It has been observed that NBD is satisfied in different types of collisions and over wide range of energies and it was observed that not only the full-phase-space multiplicity distribution can be successfully fitted by the NBD but also the distribution within central pseudo-rapidity intervals. Based on these findings, the model of cluster (or clan) cascading type has been proposed. Although, a good NBD fit can be obtained, it is observed for hadronic interactions that the presence of two weighted NBD or Double NBD (DNBD) components, one corresponding to soft production and the other to semi-hard one (mini-jets) seems to fit the data better for broad pseudo-rapidity ranges. It was found that the soft component follows KNO scaling while the semi-hard component does not. The proton-proton collision data at LHC has been analyzed to test the NBD and DNBD parametrization and test the energy dependence of the fitted parameters. It is well understood that the Standard model of Particle physics in incomplete. Our knowledge of cosmology also leaves several crucial questions unanswered, one of them being the composition of the dark matter that has been indirectly observed through astronomical observations. The primary objectives for constructing the Large Hadron Collider has been to solve these problems through the discovery of the Higgs particle and to find new physics processes that predict the production of massive non-interacting stable particles. Searches of such new physics producing heavy stable particles in its final state has been performed. Finding such signals would provide direct observation of a dark matter candidate particle. The exclusive event topology of two high energy jets and missing transverse energy has been explored to perform the above search, using ATLAS detector data. A summary of results of these preliminary searches in comparison with theoretical predictions has been presented. In order to understand and discriminate any new physics, a clear and coherent understanding of the detector response is crucial. Moreover, a detailed knowledge of the behavior of known standard model phenomena is required. A detailed description of the ATLAS detector and several important calibration techniques is discussed and their results summarized. Estimates of Standard Model physics, contributing to irreducible backgrounds to dark matter searches is presented in detail. One such physics process constituting an irreducible background is the production of the Z boson decaying into two neutrinos ([nu]) with associated jets. The observation of these events directly from data is an impossible task due to the non-interacting nature of the neutrinos. An estimate of the production cross section of these process is estimated using observations of photon ([gamma]) plus jet events and theoretical predictions. Estimated numbers for the [gamma] plus 2,3,4 and more associated jets production with uncertainties has been summarized.

Download or read book Advances in Jet Substructure at the LHC written by Roman Kogler and published by Springer Nature. This book was released on 2021-05-10 with total page 287 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces the reader to the field of jet substructure, starting from the basic considerations for capturing decays of boosted particles in individual jets, to explaining state-of-the-art techniques. Jet substructure methods have become ubiquitous in data analyses at the LHC, with diverse applications stemming from the abundance of jets in proton-proton collisions, the presence of pileup and multiple interactions, and the need to reconstruct and identify decays of highly-Lorentz boosted particles. The last decade has seen a vast increase in our knowledge of all aspects of the field, with a proliferation of new jet substructure algorithms, calculations and measurements which are presented in this book. Recent developments and algorithms are described and put into the larger experimental context. Their usefulness and application are shown in many demonstrative examples and the phenomenological and experimental effects influencing their performance are discussed. A comprehensive overview is given of measurements and searches for new phenomena performed by the ATLAS and CMS Collaborations. This book shows the impressive versatility of jet substructure methods at the LHC.

Download or read book Search for Supersymmetry Using Heavy Flavour Jets with the ATLAS Detector at the Large Hadron Collider written by Alan Tua and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Standard Model of particle physics, despite being extremely successful, is not the ultimate description of physics. The nature of dark matter is not well described, unification of the forces is not achieved and the theory is plagued by a hierarchy problem. One of the proposed solutions to these issues is supersymmetry. This thesis describes numerous searches for supersymmetry carried out using the ATLAS detector at the Large Hadron Collider. In scenarios where R-parity is conserved, supersymmetric final states contain large amounts of missing transverse energy. Furthermore, should supersymmetry correctly describe Nature, the scalar partners of the third generation quarks might be the lightest scalar quarks. The searches reported here exploit these possibilities and make use of signatures which are rich in missing transverse energy and jets coming from heavy flavour quarks. Searches are carried out for direct pair production of third generation scalar quarks as well as gluino-mediated production of these particles. A data driven technique to estimate the backgrounds coming from multijet production is described and shown to work in analyses targeting heavy flavour quarks. No significant excesses are observed in a number of analyses. In each case limits are set on the allowed masses of supersymmetric particles in a variety of phenomenological models and in specific supersymmetry breaking scenarios.

Download or read book A Search for Supersymmetry in Final States with Two Same flavor Opposite sign Leptons Jets and Missing Transverse Momentum with the ATLAS Detector written by Giulia Ripellino and published by . This book was released on 2017 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Search for Supersymmetry in Final States with Leptons with the ATLAS Detector at the Large Hadron Collider written by and published by . This book was released on 2013 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: After a short review of the Standard Model of Elementary Particle Physics and its minimal supersymmetric extension, the MSSM, a global analysis of two highly simplified supersymmetric models, the CMSSM and the NUHM1 is presented, with a focus on the fine-tuning of these models. A new, phenomenologically motivated measure for fine-tuning is introduced. In addition, a search for supersymmetry in final states with four leptons is presented, where a procedure for the consideration of trigger efficiencies with a focus on the calculation of uncertainties on the sum of event weights is given. Fina...

Download or read book Search for Supersymmetry in the Multijet and Missing Transverse Momentum Final State in Pp Collisions at 13 TeV written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for new physics is performed based on all-hadronic events with large missing transverse momentum produced in proton-proton collisions at sqrt(s)=13 TeV. The data sample, corresponding to an integrated luminosity of 2.3 inverse femtobarns, was collected with the CMS detector at the CERN LHC in 2015. The data are examined in search regions of jet multiplicity, tagged bottom quark jet multiplicity, missing transverse momentum, and the scalar sum of jet transverse momenta. The observed numbers of events in all search regions are found to be consistent with the expectations from standard model processes. Exclusion limits are presented for simplified supersymmetric models of gluino pair production. Depending on the assumed gluino decay mechanism, and for a massless, weakly interacting, lightest neutralino, lower limits on the gluino mass from 1440 to 1600 GeV are obtained, significantly extending previous limits.

Download or read book A Search for Supersymmetry in Events with a Z Boson Jets and Missing Transverse Energy in Pp Collisions with Sqrt s written by Tova Ray Holmes and published by . This book was released on 2016 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for new phenomena in final states containing a Z boson decaying to electrons or muons, jets, and large missing transverse momentum is presented. This search uses proton--proton collision data collected during 2015 and 2016 at a center of mass energy sqrt(s)=13 TeV by the ATLAS detector at the Large Hadron Collider, which correspond to an integrated luminosity of 14.7 fb-1. The search targets the pair production of supersymmetric particles, squarks or gluinos, which decay via jets and a Z boson to the lightest Supersymmetric particle, which does not interact with the ATLAS detector. Results are interpreted in simplified models of gluino-pair (squark-pair) production, and provide sensitivity to gluinos (squarks) with masses as large as 1.3 (1.0) TeV.

Download or read book Search for Supersymmetry Using Final States with One Lepton Jets and Missing Transverse Momentum with the ATLAS Detector in sqrt s written by and published by . This book was released on 2013 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: