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Kronfeld A.S.,Fermi National Accelerator Laboratory
Annual Review of Nuclear and Particle Science | Year: 2012

Quantum chromodynamics (QCD) reduces the strong interactions, in all their variety, to a simple nonabelian gauge theory. It clearly and elegantly explains hadrons at short distances, which has led to its universal acceptance. Since its advent, however, many of its long-distance, emergent properties have been believed to be true without having been demonstrated to be true. This article reviews various results in this regime that have been established with lattice gauge theory, directly from the QCD Lagrangian. This research sheds light on the origin of hadron masses, its interplay with dynamical symmetry breaking, and other intriguing features such as the phase structure of QCD. Also, nonperturbative QCD is quantitatively important to many aspects of particle physics (especially the quark flavor sector), nuclear physics, and astrophysics. This review also surveys some of the most interesting connections to those subjects. © 2012 by Annual Reviews. Source

Buckley M.R.,Fermi National Accelerator Laboratory
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Several direct detection experiments have reported positive signals consistent with a dark matter particle with a mass of approximately 7-9 GeV and a spin-independent scattering cross section of 2.5-4.8×10-41 cm2. These results do not rise to the level of discovery, but assuming that they are due to dark matter, some questions about the underlying physics can already be addressed. In this paper, I apply the effective operator formalism for dark matter Standard Model interactions to the results of the CoGeNT and CDMS silicon target experiments. I demonstrate that only one set of flavor-blind effective operators between dark matter and quarks can be consistent with the reported results in all energy regimes of interest, namely thermal freeze-out, nuclear scattering, indirect detection, and TeV-scale colliders. This set of operators implies large couplings of dark matter with heavy quarks. The alternative implies either that the new physics has nontrivial flavor structure, that the effective formalism is not applicable and so contains new states in the spectrum accessible at the LHC, or has large annihilation channels (possibly via effective operators) into noncolored Standard Model particles. © 2013 American Physical Society. Source

Bhat P.C.,Fermi National Accelerator Laboratory
Annual Review of Nuclear and Particle Science | Year: 2011

Each generation of high-energy physics experiments is grander in scale than the previousmore powerful, more complex, and more demanding in terms of data handling and analysis. The spectacular performance of the Tevatron and the beginning of operations at the Large Hadron Collider have placed us at the threshold of a new era in particle physics. The discovery of the Higgs boson, or another agent of electroweak symmetry breaking, and evidence of new physics may be just around the corner. The greatest challenge in these pursuits is to extract the extremely rare signals, if any, from the huge backgrounds that arise from known physics processes. The use of advanced analysis techniques is crucial in achieving this goal. In this review, I discuss the concepts of optimal analysis, some important advanced analysis methods, and a few examples. The judicious use of these advanced methods should enable new discoveries and produce results with better precision, robustness, and clarity. © 2011 by Annual Reviews. All rights reserved. Source

Hill C.T.,Fermi National Accelerator Laboratory
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

The Higgs mechanism may be a quantum phenomenon, i.e., a Coleman-Weinberg potential generated by the explicit breaking of scale symmetry in Feynman loops. We review the relationship of scale symmetry and trace anomalies, and we show that the Coleman-Weinberg potential can be defined as the solution to a differential renormalization group equation that follows from the trace of the improved stress tensor. We propose a simple phenomenological model with "maximal visibility" at the LHC containing a "dormant" Higgs doublet [no VEV, coupled to standard model gauge interactions SU(2)×U(1)] with a mass of ∼380GeV. We discuss the LHC phenomenology and UV challenges of such a model. We also give a schematic model in which new heavy fermions, with masses ∼230GeV, can drive a Coleman-Weinberg potential at two loops. The role of the "improved stress tensor" is emphasized, and we propose a nongravitational term, analogous to the θ term in QCD, which generates it from a scalar action. © 2014 American Physical Society. Source

Buckley M.R.,Fermi National Accelerator Laboratory
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

In order to annihilate in the early Universe to levels well below the measured dark matter density, asymmetric dark matter must possess large couplings to the standard model. In this paper, we consider effective operators which allow asymmetric dark matter to annihilate into quarks. In addition to a bound from requiring sufficient annihilation, the energy scale of such operators can be constrained by limits from direct detection and monojet searches at colliders. We show that the allowed parameter space for these operators is highly constrained, leading to nontrivial requirements that any model of asymmetric dark matter must satisfy. © 2011 American Physical Society. Source

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