![The Search for Di-lepton Signatures from Squarks and Gluinos in Pp ̄collisions at [square Root of S] PDF](https://books.google.com/books/content/images/frontcover/6vuJRb8sNIcC?fife=w150-h200)
Author: Richard Joyner GenikPublisher:
ISBN:
Category : Particles (Nuclear physics)
Languages : en
Pages : 328
Book Description
The Search for Di-lepton Signatures from Squarks and Gluinos in Pp ̄collisions at [square Root of S]
![The Search for Di-lepton Signatures from Squarks and Gluinos in Pp ̄collisions at [square Root of S] PDF](https://books.google.com/books/content/images/frontcover/6vuJRb8sNIcC?fife=w80-h100)
Author: Richard Joyner GenikPublisher:
ISBN:
Category : Particles (Nuclear physics)
Languages : en
Pages : 328
Book Description
Searching for Squarks
Author: Samuel JonesPublisher: Springer Nature
ISBN: 3030542882
Category : Science
Languages : en
Pages : 223
Book Description
This thesis focuses on searches for squarks with the ATLAS detector in "compressed" scenarios where the scalar top is very close in mass to the lightest supersymmetric particle. These models are theoretically appealing because the presence of a quasi-degenerate scalar top enhances the self-annihilation cross-section of the lightest supersymmetric particle, acting therefore as a regulator of the dark matter relic density. Two main analyses are presented: the first is a search for scalar tops decaying to charm quarks. The identification of jets originating from the charm quark is very challenging due to its short lifetime. The calibration of tools for charm-tagging has paved the way to measuring the decay of the Higgs boson to pairs of charm quarks. The second analysis presented is the development of a novel technique for reconstructing low momentum b-hadrons. This tool has enabled the ATLAS collaboration to explore topologies that were previously inaccessible.
Searches for New Physics at Colliders
Author: My Phuong Thi LePublisher: Stanford University
ISBN:
Category :
Languages : en
Pages : 277
Book Description
The turning-on of the Large Hadron Collider is the momentous milestone in our quest for new physics beyond the Standard Model. Soon, we will be presented with the task of detecting, identifying, and studying the possibly large parameter space of the underlying model. In this thesis, we will look at some possible extensions to the SM, their signatures at colliders, and possible search strategies to explore the new physics in a model-independent way. In chapter 2, we study the extended neutral gauge sector of the Littlest Higgs model at the 500 GeV e+e- collider using the fermion pair production and Higgs associate production channel. We find that these channels can provide an accurate determination of the fundamental parameters and thus allows the verification of the little Higgs mechanism designed to cancel the Higgs mass quadratic divergence. In chapter 3, we study the ATLAS supersymmetry searches proposed for the 14 TeV pp collider using the $\sim$ 70k models of the phenomenological Minimal Supersymmetric Model (pMSSM) moldel set, that have survived many theoretical and experimental constraints. Since pMSSM does not make any simplifying assumptions about its SUSY-breaking mechanism at high scale, this encompasses a broad class of Supersymmetric models. We find that even though these searches were optimized mostly for mSUGRA signals, they are relatively robust in observing the more general pMSSM models. For the case of models in which squarks and gluinos have mass below 1 TeV, essentially all of these models ($> 99\%$) were observable in at least one of these searches, with 1 $fb^{-1}$ of integrated luminosity allowing for an uncertainty of 50\% in the SM background. We found that 0-lepton searches are the most powerful searches, while searches with 1-2 leptons do not have coverage as good as has been shown for mSUGRA. We then study possible reasons why a model could not be observed. These difficult models mostly include those with long-lived charginos which lead to small Missing Tranverse Energy (MET) and models with squeezed spectra which lead to soft jets that fail the jet cuts. In chapter 4, we study similar searches that have been carried out by ATLAS at the 7 TeV LHC. We found that systematic uncertainty again plays an important role in determining the coverage of the searches. This is especially true for searches with a large SM background, such as $n$-jet 0 lepton searches. We study the implication of a null result from the 7 TeV LHC. We find that the degree of fine-tuning in the pMSSM depends on the prior in which we scan our 19-dimensional space, but overall it is not as large as in mSUGRA. We find that a null result at the 7 TeV with $10 fb^{-1}$ and 20\% systematic errors would imply a need for a higher energy e+e- machine than the 500 GeV ILC to study Supersymmetry. Continuing on along the line of Supersymmetry, in chapter 5 we explore the possibility of adding one more generation to the MSSM (4GMSSM). We find that the CP-odd A boson can be very light due to the contribution of the heavy 4th generation fermion loops while all other Higgs particles (including the CP-even {\it h}) are all quite heavy. The parameter $tan(\beta)$ is strongly constrained to be between 0.5 and 2 due to perturbativity requirements on Yukawa couplings. We study the electroweak constraints as well as collider signatures on the possibility of a light A of mass $\sim$115 GeV. As for an LHC discovery, we find that this light A can be seen in the standard 2-photon Higgs search channel with cross-section more than an order of magnitude greater than that of the SM Higgs. In the last two chapters, we study possible search strategies to explore the new physics in a model-independent way. In chapter 6, we attempt to show how one could be largely agnostic about the underlying model in exploring the complete kinematically-allowed parameter space of pair-produced color octet particles (with mass $m_{\tilde{g}}$) that each directly decay into two jets plus a neutral stable particle (with mass $m_{\tilde{B}}$) that would escape the detectors and appear as MET. The kinematics of this process can be completely described by two parameters $m_{\tilde {g}}$ and $m_{\tilde {B}}$ , and in particular their splitting determines the softness or hardness of jets from the decay products. In order to cover the whole parameter space, one would need separate searches for different regions. We show that optimizing the final cuts for every ($m_{\tilde {g}}$, $m_{\tilde {B}}$) point, and combining all searches, can extend the coverage significantly. Since this is just based on the kinematics of the decay, this result can be easily interpreted for any model with this decay topology. In chapter 7, we carry this model-independent approach further in jets plus missing energy searches, by proposing that one should bin the measured data (or simulated SM background) differentially in MET and $H_T$ (scalar sum of invisible energy) for each search, and use them to set limits on any model of interest. We demonstrate this technique by carrying out a search similar to that studied in chapter 6, with one added decay step for the color octet particle, mainly it decays to 2 jets and another particle (with mass $m_{\tilde {W}}$) and it in turn decays to the neutral stable particle and 2 jets. We study different kinematic regions and set bounds in this 3-dimensional parameter space ($m_{\tilde {g}}$, $m_{\tilde {W}}$, $m_{\tilde {B}}$).
Perspectives on Supersymmetry II
Author: G. L. KanePublisher: World Scientific
ISBN: 9814307505
Category : Science
Languages : en
Pages : 604
Book Description
Supersymmetry is at an exciting stage of development. It extends the Standard Model of particle physics into a more powerful theory that both explains more and allows more questions to be addressed. Most importantly, it opens a window for studying and testing fundamental theories at the Planck scale. Experimentally we are finally entering the intensity and energy and sensitivity regions where superpartners and supersymmetric dark matter candidates are likely to be detected, and then studied. There has been progress in understanding the remarkable physics implications of supersymmetry, including the derivation of the Higgs mechanism, the unification of the Standard Model forces, cosmological connections such as a candidate for the cold dark matter of the universe and consequences for understanding the cosmological history of the universe, and more. This volume begins with an excellent pedagogical introduction to the physics and methods and formalism of supersymmetry which is accessible to anyone with a basic knowledge of the Standard Model of particle physics.Next is an overview of open questions, followed by chapters on topics such as how to detect superpartners and tools for studying them, the current limits on superpartner masses as we enter the LHC era, the lightest superpartner as a dark matter candidate in thermal and non-thermal cosmological histories, and associated Z'' physics. Most chapters have been extended and updated from the earlier edition and some are new. This superb book will allow interested physicists to understand the coming experimental and theoretical progress in supersymmetry and the implications of discoveries of superpartners, and will also help students and workers to quickly learn new aspects of supersymmetry they want to pursue.
Search for Scalar Top Quarks and Higgsino-Like Neutralinos
Author: Takuya NobePublisher: Springer
ISBN: 9811000034
Category : Science
Languages : en
Pages : 229
Book Description
This book reports a search for theoretically natural supersymmetry (SUSY) at the Large Hadron Collider (LHC). The data collected with the ATLAS detector in 2012 corresponding to 20 /fb of an integrated luminosity have been analyzed for stop pair production in proton–proton collisions at a center-of-mass energy of 8 TeV at the Large Hadron Collider (LHC) in the scenario of the higgsino-like neutralino. The author focuses on stop decaying into a bottom quark and chargino. In the scenario of the higgsino-like neutralino, the mass difference between charginos and neutralinos (Δm) is expected to be small, and observable final-state particles are likely to have low-momentum (soft). The author develops a dedicated analysis with a soft lepton as a probe of particles from chargino decay, which suppresses the large amount of backgrounds. As a result of the analysis, no significant SUSY signal is observed. The 95% confidence-level exclusion limits are set to masses of stop and neutralino assuming Δm = 20 GeV. The region with ΔM (the mass difference between stop and neutralino) 70 GeV is excluded for the first time at stop mass of less than 210 GeV. The author also excludes the signals with ΔM 120 GeV up to 600 GeV of stop mass with neutralino mass of less than 280 GeV. The author clearly shows very few remaining parameter spaces for light stop (e.g., topology of stop decay is extremely similar to the SM top quark) by combining his results and previous ATLAS analyses. His results provide a strong constraint to searches for new physics in the future.
Supersymmetry And Unification Of Fundamental Interactions (Susy 93) - Proceedings Of The International Workshop
Author: Pran NathPublisher: World Scientific
ISBN: 9814552232
Category :
Languages : en
Pages : 646
Book Description
The recent high precision results from the LEP supercollider at CERN appear favorable for supergravity unification of the electroweak and the strong forces. The proceedings of the SUSY 93 Workshop focus on further precise predictions of unification which may be observed in the laboratory. In addition, the proceedings cover a wide range of other topics in supersymmetry, supergravity, particle physics, string theory and cosmology and their interconnections. They include both theoretical and experimental papers, hence presenting a complete and comprehensive picture of this important subject.
Hadron Collider Physics - Proceedings Of The Xi Symposium
Author: D BiselloPublisher: World Scientific
ISBN: 9814547026
Category :
Languages : en
Pages : 814
Book Description
The proceedings of this series of annual symposia represent an extensive summary of the experimental and theoretical status of high energy physics at hadron colliders. This volume discusses the latest results on top and beauty physics, QCD, electroweak physics and searches for new particles. The prospects of this field for LHC, Tevatron and Hera machines are also reported.
Perspectives On Lhc Physics
Author: Gordon KanePublisher: World Scientific
ISBN: 9814472190
Category : Science
Languages : en
Pages : 352
Book Description
The Large Hadron Collider (LHC), located at CERN, Geneva, Switzerland, is the world's largest and highest energy and highest intensity particle accelerator. Here is a timely book with several perspectives on the hoped-for discoveries from the LHC.This book provides an overview on the techniques that will be crucial for finding new physics at the LHC, as well as perspectives on the importance and implications of the discoveries. Among the accomplished contributors to this book are leaders and visionaries in the field of particle physics beyond the Standard Model, including two Nobel Laureates (Steven Weinberg and Frank Wilczek), and presumably some future Nobel Laureates, plus top younger theorists and experimenters. With its blend of popular and technical contents, the book will have wide appeal, not only to physical scientists but also to those in related fields.
Dark Matter In Astro- And Particle Physics, Dark '96
Author: Hans Volker Klapdor-kleingrothausPublisher: World Scientific
ISBN: 9814546364
Category :
Languages : en
Pages : 758
Book Description
This volume contains the talks presented at the International Workshop on Aspects of Dark Matter in Astro- and Particle Physics (DARK '96). It provides a thorough presentation and discussion of the topic of dark matter, which currently seems to be one of the most exciting problems of modern physics, in the perspectives of different disciplines like astronomy, astrophysics, cosmology and particle physics.The lectures and talks range from astronomical evidence in galaxies and galaxy clusters, recent information provided by X rays (ROSAT satellite) and by observation of MACHOs, to early universe and particle physics solutions to the dark matter problem, including simultaneous solutions to the problems of baryogenesis and dark matter. Beyond the favoured supersymmetric candidates, the more exotic dark matter proposals are also discussed. The experimental section examines the most recent efforts in direct and indirect experiments, including new techniques like cryogenic detectors and superheated droplet detectors, as well as efforts with large scale underground detectors like MACRO, Baksan, Baikal and AMANDA. Also, the potential of present and future (LHC) high energy accelerators is thoroughly discussed. A section on hot dark matter gives the current status of experiments searching for a neutrino mass, like double beta decay and neutrino oscillation experiments, including intermediate scale long baseline experiments.
Particles And Fields - Proceedings Of The Ixth Jorge Andre Swieca Summer School
Author: Joao Carlos Alves BarataPublisher: World Scientific
ISBN: 9814544957
Category :
Languages : en
Pages : 526
Book Description
This book contains the proceedings of the IXth Jorge André Swieca Summer School — Particles and Fields — held at Campos do Jordao in February 1997.It surveys some of the most interesting research topics in theoretical physics, like duality theory, quantum field theory in curved space-time, supersymmetry and the standard model, differential geometry and its applications in physics and cosmic ray physics.