The Large Hadron Collider (LHC), located at CERN, Geneva, Switzerland, is the world's largest and highest energy and highest intensity particle accelerator. 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 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.
These proceedings cover the latest results in Tevatron Collider Physics, LEP results, and results from other High Energy Physics Laboratories. The volume will consist of plenary and parallel contributions on the following subjects: Heavy Quark Physics, Physics Beyond the Standard Model, Astrophysics and Non-Accelerator Physics.
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.
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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 ($m_{\tilde {g}}$, $m_{\tilde {W}}$, $m_{\tilde {B}}$).
The objective of the workshop series “The Identification of Dark Matter” is to assess critically the status of work attempting to identify what constitutes dark matter; in particular, to consider what techniques are currently being used, how successful they are, and what new techniques are likely to improve the prospects for identifying dark matter candidates in the future. This proceedings volume includes reviews on major particle astrophysics topics in the field of dark matter, as well as short contributed papers.
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.
This volume addresses the important questions at the interface of particle physics, cosmology and nuclear astrophysics. It includes the latest results from LEP 2, primordial nucleosynthesis and dark matter, experiments to measure the cosmic background radiation and experiments in the laboratory with radioactive beams to ascertain the importance of astrophysics in the universe. Also presented are the new results at highest momentum transfer in positron-proton collisions from HERA.
