Search Strategies for New Physics at the LHC PDF Download

Author: Daniele Spier Moreira Alves
Publisher: Stanford University
ISBN:
Category :
Languages : en
Pages : 122

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Book Description
The LHC is in the frontline of experimental searches for New Physics beyond the Standard Model of Particle Physics. Its power is accompanied by no smaller challenges in analyzing and interpreting its results. In this thesis I explore ways to parameterize new physics phenomena, design search strategies that are sensitive to them, and interpret experimental results in general new physics contexts. In particular, I discuss interpretations of the first ATLAS analysis for supersymmetry with 70/nb of integrated luminosity. I also carry a careful investigation of comprehensive search strategies for new physics with jets and missing energy signatures, and estimate the sensitivity bounds of the 7 TeV LHC to new colored particles decaying to jets and and a neutral particle that escapes detection. Finally, I discuss the implications of the recent LHC excesses hinting to a Higgs boson with mass in the range 142-147 GeV. If confirmed, this range for the Higgs mass will be an important evidence for Split Supersymmetry. I work out the phenomenological predictions of this scenario that will be tested in the very near future by a variety of experiments, including direct and indirect dark matter detection, EDM experiments searching for CP violation and the 7 TeV run of the LHC.

Author: My Phuong Thi Le
Publisher: Stanford University
ISBN:
Category :
Languages : en
Pages : 277

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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 ($m_{\tilde {g}}$, $m_{\tilde {W}}$, $m_{\tilde {B}}$).

Author: Saranya Samik Ghosh
Publisher: Springer Nature
ISBN: 3030537838
Category : Science
Languages : en
Pages : 77

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Book Description
This primer describes the general model independent searches for new physics phenomena beyond the Standard Model of particle physics. First, the motivation for performing general model independent experimental searches for new physics is presented by giving an overview of the current theoretical understanding of particle physics in terms of the Standard Model of particle physics and its shortcomings. Then, the concept and features of general model independent search for new physics at collider based experiments is explained. This is followed by an overview of such searches performed in past high energy physics experiments and the current status of such searches, particularly in the context of the experiments at the LHC. Finally, the future prospects of such general model independent searches, with possible improvements using new tools such as machine learning techniques, is discussed.

Author: A. Astbury
Publisher: World Scientific
ISBN: 9812774424
Category : Science
Languages : en
Pages : 348

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Book Description
This proceedings volume contains pedagogical lectures on theoretical and experimental particle physics, cosmology and atomic trap physics. It also includes additional contributions that provide up-to-date information on new experimental results from accelerators, underground laboratories, and nuclear astrophysics. This combination of pedagogical talks and topical short talks provides comprehensive information to researchers in the fields of particle physics, cosmology and atomic trap physics. Sample Chapter(s). Chapter 1: New Physics in B and K Decays (1,704 KB). Contents: Cosmic Ray Velocity and Electric Charge Measurements in the AMS Experiment (L Arruda); Flavor and Chiral Oscillations with Dirac Spinors (A E Bernardini); Modification of the Casimir Effect Due to a Minimal Length Scale (U Harbach); Parton Energy Loss, Saturation, and Recombination at BRAHMS (E-J Kim); Spatial Confinement and Thermal Deconfinement in the Compactified Gross-Neveu Model (J M C Malbouisson); Currents on Superconducting Strings in an Unusual Environment (M A Metlitski); QCD Results at CDF (O Norniella); Quantization of Galilean Covariant Fields (E S Santos); Physics of Heavy Flavour at CDF (S Torre); Resonance Production at STAR (H Zhang); and other papers. Readership: Graduate students, researchers and academics in high energy physics, particle physics and astrophysics.

Author: Ian Brock
Publisher: John Wiley & Sons
ISBN: 3527634975
Category : Science
Languages : en
Pages : 437

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Book Description
Written by authors working at the forefront of research, this accessible treatment presents the current status of the field of collider-based particle physics at the highest energies available, as well as recent results and experimental techniques. It is clearly divided into three sections; The first covers the physics -- discussing the various aspects of the Standard Model as well as its extensions, explaining important experimental results and highlighting the expectations from the Large Hadron Collider (LHC). The second is dedicated to the involved technologies and detector concepts, and the third covers the important - but often neglected - topics of the organisation and financing of high-energy physics research. A useful resource for students and researchers from high-energy physics.

Author: Paolo Calafiura
Publisher: World Scientific
ISBN: 9811234043
Category : Science
Languages : en
Pages : 829

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Book Description
The Higgs boson discovery at the Large Hadron Collider in 2012 relied on boosted decision trees. Since then, high energy physics (HEP) has applied modern machine learning (ML) techniques to all stages of the data analysis pipeline, from raw data processing to statistical analysis. The unique requirements of HEP data analysis, the availability of high-quality simulators, the complexity of the data structures (which rarely are image-like), the control of uncertainties expected from scientific measurements, and the exabyte-scale datasets require the development of HEP-specific ML techniques. While these developments proceed at full speed along many paths, the nineteen reviews in this book offer a self-contained, pedagogical introduction to ML models' real-life applications in HEP, written by some of the foremost experts in their area.

Author: Antonino Zichichi
Publisher: World Scientific
ISBN: 9814472328
Category : Science
Languages : en
Pages : 457

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Book Description
This volume is a collection of lectures given by distinguished physicists from around the world, covering the most recent advances in theoretical physics and the latest results from current experimental facilities.Following one of the principal aims of the School — to encourage and promote young physicists to achieve recognition at an international level — the students who distinguished themselves for the excellence of their research were given the opportunity to publish their presentations in this volume.

Author: Guiyu Huang
Publisher:
ISBN:
Category :
Languages : en
Pages : 208

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Book Description

Author: Alan Astbury
Publisher: World Scientific
ISBN: 9812776095
Category : Science
Languages : en
Pages : 487

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Book Description
This proceedings volume contains the latest results from the field of particle physics. The contributions cover the current status of all the Large Hadron Collider (LHC) experiments, the implications of the LHC for cosmology, and the search for dark matter and nuclear astrophysics. It also includes work on the current status of the future International Linear Collider (ILC).

Author: Zygmunt Ajduk
Publisher: World Scientific
ISBN: 9814551767
Category :
Languages : en
Pages : 502

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Book Description
This volume gives an up-to-date, useful review of the recent results and new ideas concerning the following topics: precision tests of the standard model, search for Higgs bosons, CP violation, flavour physics, neutrino physics, testing extensions of the standard model, supersymmetry, particle physics, cosmology and new results in strong interactions.