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Higgs, Supersymmetry and Dark Matter After Run I of the LHC

Author: Béranger Dumont

Publisher: Springer

Published: 2016-09-21

Total Pages: 271

ISBN-13: 3319449567

This work was nominated as an outstanding PhD thesis by the LPSC, Université Grenoble Alpes, France. The LHC Run 1 was a milestone in particle physics, leading to the discovery of the Higgs boson, the last missing piece of the so-called "Standard Model" (SM), and to important constraints on new physics, which challenge popular theories like weak-scale supersymmetry. This thesis provides a detailed account of the legacy of the LHC Run 1 ≤¥regarding these aspects. First, the SM and the need for its extension are presented in a concise yet revealing way. Subsequently, the impact of the LHC Higgs results on scenarios of new physics is assessed in detail, including a careful discussion of the relevant uncertainties. Two approaches are considered: generic modifications of the Higgs couplings, possibly arising from extended Higgs sectors or higher-dimensional operators; and tests of specific new physics models. Lastly, the implications of the null results of the searches for new physics are discussed with a particular focus on supersymmetric dark matter candidates. Here as well, two approaches are presented: the "simplified models" approach, and recasting by event simulation. This thesis stands out for its educational approach, its clear language and the depth of the physics discussion. The methods and tools presented offer readers essential practical tools for future research.

Higgs, Supersymmetry and Dark Matter After Run I of the LHC

Author: Béranger Dumont

Publisher:

Published: 2014

Total Pages: 0

ISBN-13:

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Two major problems call for an extension of the Standard Model (SM): the hierarchy problem in the Higgs sector and the dark matter in the Universe. The discovery of a Higgs boson with mass of about 125 GeV was clearly the most significant piece of news from CERN's Large Hadron Collider (LHC). In addition to representing the ultimate triumph of the SM, it shed new light on the hierarchy problem and opened up new ways of probing new physics. The various measurements performed at Run I of the LHC constrain the Higgs couplings to SM particles as well as invisible and undetected decays. In this thesis, the impact of the LHC Higgs results on various new physics scenarios is assessed, carefully taking into account uncertainties and correlations between them. Generic modifications of the Higgs coupling strengths, possibly arising from extended Higgs sectors or higher-dimensional operators, are considered. Furthermore, specific new physics models are tested. This includes, in particular, the phenomenological Minimal Supersymmetric Standard Model.While a Higgs boson has been found, no sign of beyond the SM physics was observed at Run I of the LHC in spite of the large number of searches performed by the ATLAS and CMS collaborations. The implications of the negative results obtained in these searches constitute another important part of this thesis. First, supersymmetric models with a dark matter candidate are investigated in light of the negative searches for supersymmetry at the LHC using a so-called "simplified model" approach. Second, tools using simulated events to constrain any new physics scenario from the LHC results are presented. Moreover, during this thesis the selection criteria of several beyond the SM analyses have been reimplemented in the MadAnalysis 5 framework and made available in a public database.

The Higgs and Supersymmetry at Run II of the LHC.

Author:

Publisher:

Published: 2016

Total Pages: 4

ISBN-13:

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Prof. David Shih was supported by DOE grant DE-SC0013678 from April 2015 to April 2016. His research during this year focused on the phenomenology of super- symmetry (SUSY) and maximizing its future discovery potential at Run II of the LHC. SUSY is one of the most well-motivated frameworks for physics beyond the Standard Model. It solves the \naturalness" or \hierarchy" problem by stabilizing the Higgs mass against otherwise uncontrolled quantum corrections, predicts \grand uni cation" of the fundamental forces, and provides many potential candidates for dark matter. However, after decades of null results from direct and indirect searches, the viable parameter space for SUSY is increasingly constrained. Also, the discovery of a Standard Model-like Higgs with a mass at 125 GeV places a stringent constraint on SUSY models. In the work supported on this grant, Shih has worked on four di erent projects motivated by these issues. He has built natural SUSY models that explain the Higgs mass and provide viable dark matter; he has studied the parameter space of \gauge mediated supersymmetry breaking" (GMSB) that satis es the Higgs mass constraint; he has developed new tools for the precision calculation of avor and CP observables in general SUSY models; and he has studied new techniques for discovery of supersymmetric partners of the top quark.

Supersymmetric Dark Matter After LHC Run 1

Author:

Publisher:

Published: 2015

Total Pages: 21

ISBN-13:

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Different mechanisms operate in various regions of the MSSM parameter space to bring the relic density of the lightest neutralino, [chi]~01, assumed here to be the lightest SUSY particle (LSP) and thus the dark matter (DM) particle, into the range allowed by astrophysics and cosmology. These mechanisms include coannihilation with some nearly degenerate next-to-lightest supersymmetric particle such as the lighter stau [tau]~1, stop t~1 or chargino [chi]~"1, resonant annihilation via direct-channel heavy Higgs bosons H / A, the light Higgs boson h or the Z boson, and enhanced annihilation via a larger Higgsino component of the LSP in the focus-point region. These mechanisms typically select lower-dimensional subspaces in MSSM scenarios such as the CMSSM, NUHM1, NUHM2, and pMSSM10. We analyze how future LHC and direct DM searches can complement each other in the exploration of the different DM mechanisms within these scenarios. We find that the [tau]~1 coannihilation regions of the CMSSM, NUHM1, NUHM2 can largely be explored at the LHC via searches for /ET events and long-lived charged particles, whereas theirH / A funnel, focus-point and [chi]~"1 coannihilation regions can largely be explored by the LZ and Darwin DM direct detection experiments. Furthermore, we find that the dominant DM mechanism in our pMSSM10 analysis is [chi]~"1 coannihilation: parts of its parameter space can be explored by the LHC, and a larger portion by future direct DM searches.

Search Strategies for New Physics at the LHC

Author: Daniele Spier Moreira Alves

Publisher: Stanford University

Published: 2011

Total Pages: 122

ISBN-13:

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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.

Collider

Author: Paul Halpern

Publisher: John Wiley & Sons

Published: 2009-08-03

Total Pages: 274

ISBN-13: 0470286202

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An accessible look at the hottest topic in physics and the experiments that will transform our understanding of the universe The biggest news in science today is the Large Hadron Collider, the world's largest and most powerful particle-smasher, and the anticipation of finally discovering the Higgs boson particle. But what is the Higgs boson and why is it often referred to as the God Particle? Why are the Higgs and the LHC so important? Getting a handle on the science behind the LHC can be difficult for anyone without an advanced degree in particle physics, but you don't need to go back to school to learn about it. In Collider, award-winning physicist Paul Halpern provides you with the tools you need to understand what the LHC is and what it hopes to discover. Comprehensive, accessible guide to the theory, history, and science behind experimental high-energy physics Explains why particle physics could well be on the verge of some of its greatest breakthroughs, changing what we think we know about quarks, string theory, dark matter, dark energy, and the fundamentals of modern physics Tells you why the theoretical Higgs boson is often referred to as the God particle and how its discovery could change our understanding of the universe Clearly explains why fears that the LHC could create a miniature black hole that could swallow up the Earth amount to a tempest in a very tiny teapot "Best of 2009 Sci-Tech Books (Physics)"-Library Journal "Halpern makes the search for mysterious particles pertinent and exciting by explaining clearly what we don't know about the universe, and offering a hopeful outlook for future research."-Publishers Weekly Includes a new author preface, "The Fate of the Large Hadron Collider and the Future of High-Energy Physics" The world will not come to an end any time soon, but we may learn a lot more about it in the blink of an eye. Read Collider and find out what, when, and how.

Physics Beyond the Standard Model

Author:

Publisher:

Published: 2008

Total Pages: 205

ISBN-13:

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The Standard Model (SM) of particle physics is remarkably successful and has survived two decades of precision tests at high energy particle accelerators. However, it is known to be incomplete, and there are reasons to believe that there is new physics at energy scales that will soon be probed in greater detail than ever before by the Large Hadron Collider (LHC), a proton-proton accelerator being built near Geneva. This thesis contains a diverse set of topics that may broadly be described as physics beyond the SM. In Chapter 2, implications of current experimental constraints are presented for the stop masses and mixing in the Minimal Supersymmetric Standard Model (MSSM), a well-motivated candidate for physics beyond the SM. It is found, for example, that lower bounds on the stop masses are as large as 1 TeV assuming no stop-mixing. Chapter 3 presents the regions in the MSSM with the minimal amount of fine-tuning of electroweak symmetry breaking. The minimal amount of tuning increases enormously for a Higgs mass beyond 120 GeV. Supersymmetry cannot be an exact symmetry, and one possibility is that our Universe is in a long-lived metastable state with broken supersymmetry. In Chapter 4, a generic model with this property is constructed in which all the relevant parameters, including the supersymmetry breaking scale, are generated dynamically. This model has several interesting model-building features including an explicitly and spontaneously broken R-symmetry, a singlet, a large global symmetry, naturalness, renormalizability, and a "pseudo-runaway'' direction. In Chapter 5, a simple extension of the SM with weakly interacting non-chiral dark matter particles is presented. Such particles can be detected at a future direct-detection experiment. There are a wide variety of possible discovery signatures for new physics at the LHC. A discovery signature with a large SM background that has not been well studied involves multi-jet events without leptons and/or missing energy. In Chapter 6, it is found that using innovative search strategies pair production of new coloured adjoint fermions producing a pure six-jet final state can be detected up to a mass of about 650-700 GeV with 10 fb-1 of integrated luminosity.

Dark Matter and Super Symmetry

Author:

Publisher:

Published: 2016

Total Pages:

ISBN-13:

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The Large Hadron Collider (LHC) at CERN in Geneva, Switzerland, is one of the largest machines on this planet. It is built to smash protons into each other at unprecedented energies to reveal the fundamental constituents of our universe. The 4 detectors at the LHC record multi-petabyte datasets every year. The scientific analysis of this data requires equally large simulation datasets of the collisions based on the theory of particle physics, the Standard Model. The goal is to verify the validity of the Standard Model or of theories that extend the Model like the concepts of Supersymmetry and an explanation of Dark Matter. I will give an overview of the nature of simulations needed to discover new particles like the Higgs boson in 2012, and review the different areas where simulations are indispensable: from the actual recording of the collisions to the extraction of scientific results to the conceptual design of improvements to the LHC and its experiments.

Testing Supersymmetry at Future High Energy Colliders, in Dark Matter and High Precision Experiments

Author: Amin Abou Ibrahim

Publisher:

Published: 2020

Total Pages: 386

ISBN-13:

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"The observation of the Higgs boson at 125 GeV indicates that the size of weak scale supersymmetry lies in the TeV region which makes the discovery of supersymmetry at the LHC more challenging. Here we discuss the potential for the discovery of sparticles and of heavier Higgs bosons at HL-LHC and also argue in favor of construction of a machine with higher energy, i.e., a 27 TeV high energy LHC (HE-LHC). We carry out a comparative study for the discovery of electroweakinos and heavier Higgs bosons at the two machines. For a number of test model points, it is found that the discovery of sparticles (or of heavier Higgs) would require a HL-LHC run between 5-8 years while the same parameter points can be discovered in a period of few weeks to ~ 1.5 yr at HE-LHC. The analysis indicates that the HE-LHC possibility should be seriously pursued as it would significantly increase the discovery reach for sparticles and for heavier Higgs beyond the reach of HL-LHC and decrease the run period for discovery for models which are also discoverable at HL-LHC. In this work we also discuss the possibility of detecting hidden sector dark matter at the LHC. Specifically we analyze the case when the dark matter resides in the hidden sector while a charged sparticle is the LSP of MSSM. We show that for the case when the portal to the hidden sector is via gauge kinetic mixing and Stueckelberg mass mixing generating feeble interactions between the visible sector and the hidden sector, the charged LSP of MSSM will decay into the hidden sector dark matter. In this case the charged particle will be long-lived and will leave a track inside the detector. We considered two cases: (i) a stau which produces a track but decays inside the detector and can be identified as a decaying particle with missing energy, (ii) a stop which produces an R-hadron and decays outside. Each case points to a hidden sector dark matter. For the case (ii) future detectors such as MATHUSLA and FASER will explore the lifetime frontier and are capable of detecting long-lived particles such as the stop which decay further away from their production vertex and they will provide further test of the hidden sector dark matter models. We show that models where the dark matter resides in the hidden sector require both the freeze-out and the freeze-in mechanisms to produce the desired amount of dark matter consistent with the Planck experiment. We also show that the existence of a hidden sector can expand the parameter space of natural supersymmetry. Finally we discuss how precision physics provides another avenue for the exploration of new physics beyond the standard model"--Author's abstract.

Supersymmetry and Beyond

Author: Gordon Kane

Publisher: Basic Books

Published: 2013-05-14

Total Pages: 218

ISBN-13: 0465080464

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The epic story of the quest to uncover a fully unified theory of physics, revised to reflect the possible discovery of the Higgs Boson.