Annual Review of Nuclear and Particle Science - Volume 57, 2007

From 1983 to 2002, the Indiana Cooler was constructed and operated at the Indiana University Cyclotron Facility. During that period, a relatively small group of people built an accelerator complex, explored the new technology of electron cooling, and demonstrated its usefulness in nuclear and particle physics. This review recounts the history of the project, describes the facility, and summarizes the scientific results in atomic, nuclear, and particle physics, and in the physics of beams.

This review gives a brief introduction to chiral perturbation theory in its various settings. We discuss some applications of recent interest, including chiral extrapolations for lattice gauge theory.

Because the quark-gluon plasma (QGP) reveals some obvious similarities to the well-known electromagnetic plasma (EMP), an accumulated knowledge on EMPs can be used in QGP studies. After discussing similarities and differences of the two systems, we present the theoretical tools used to describe the plasmas. The tools include kinetic theory, hydrodynamic approach, and diagrammatic perturbative methods. We consider collective phenomena in the plasma, with a particular emphasis on instabilities that crucially influence the temporal evolution of the system. Finally, properties of strongly coupled plasma are discussed.

We review recent progress in applying the AdS/CFT correspondence to finite-temperature field theory. In particular, we show how the hydrodynamic behavior of field theory is reflected in the low-momentum limit of correlation functions computed through a real-time AdS/CFT prescription, which we formulate. We also show how the hydrodynamic modes in field theory correspond to the low-lying quasi-normal modes of the AdS black p-brane metric. We provide proof of the universality of the viscosity/entropy ratio within a class of theories with gravity duals and formulate a viscosity bound conjecture. Possible implications for real systems are mentioned.

We provide a qualitative review of flux compactifications of string theory, focusing on broad physical implications and statistical methods of analysis.

To introduce the ideas of statistical and systematic errors, this review first describes a simple pendulum experiment. We follow with a brief discussion of the Bayesian and frequentist approaches. Two widely used applications of statistical techniques in particle physics data include extracting ranges for parameters of interest (e.g., mass of the W boson, cross section for top production, neutrino mixing angles, etc.) and assessing the significance of possible signals (e.g., is there evidence for Higgs boson production?). These two topics are first discussed in the absence of systematics, and then methods of incorporating systematic effects are described. We give a detailed discussion of a Bayesian approach to setting upper limits on a Poisson process in the presence of background and/or acceptance uncertainties. The relevance of the choice of priors and how this affects the coverage properties of the method are described.

Two-photon exchange contributions to elastic electron scattering are reviewed. The apparent discrepancy between unpolarized Rosenbluth and polarization transfer experiments in the extraction of elastic nucleon form factors is discussed, as well as the understanding of this puzzle in terms of two-photon exchange corrections. Calculations of such corrections within both partonic and hadronic frameworks are reviewed. In view of recent spin-dependent electron scattering data, the relation of the two-photon exchange process to the hyperfine splitting in hydrogen is critically examined. The imaginary part of the two-photon exchange amplitude as can be accessed from the beam-normal spin asymmetry in elastic electron-nucleon scattering is reviewed. Further extensions and open issues in this field are outlined.

We review the theoretical background, experimental techniques, and phenomenology of what is known in relativistic heavy ion physics as the Glauber model, which is used to calculate geometric quantities. A brief history of the original Glauber model is presented, with emphasis on its development into the purely classical, geometric picture used for present-day data analyses. Distinctions are made between the optical limit and Monte Carlo approaches, which are often used interchangeably but have some essential differences in particular contexts. The methods used by the four RHIC experiments are compared and contrasted, although the end results are reassuringly similar for the various geometric observables. Finally, several important RHIC measurements are highlighted that rely on geometric quantities, estimated from Glauber calculations, to draw insight from experimental observables. The status and future of Glauber modeling in the next generation of heavy ion physics studies is briefly discussed.

We intend to show how fundamental science is drawn from the patterns in the temperature and polarization fields of the cosmic microwave background (CMB) radiation, and thus to motivate the field of CMB research. We discuss the field's history, potential science and current status, contaminating foregrounds, detection and analysis techniques, and future prospects. Throughout the review we draw comparisons to particle physics, a field that has many of the same goals and that has gone through many of the same stages.

We survey the theory and experimental tests for the propagation of cosmic rays in the Galaxy up to energies of 10¹⁵ eV. A guide to the previous reviews and essential literature is given, followed by an exposition of basic principles. The basic ideas of cosmic-ray propagation are described, and the physical origin of its processes is explained. The various techniques for computing the observational consequences of the theory are described and contrasted. These include analytical and numerical techniques. We present the comparison of models with data, including direct and indirect—especially γ-ray—observations, and indicate what we can learn about cosmic-ray propagation. Some important topics, including electron and antiparticle propagation, are chosen for discussion.

This review summarizes effective field theory techniques, which are the modern theoretical tools for exploiting the existence of hierarchies of scale in a physical problem. The general theoretical framework is described and evaluated explicitly for a simple model. Power-counting results are illustrated for a few cases of practical interest, and several applications to quantum electrodynamics are described.

Although developed and first demonstrated more than 40 years ago, germanium detectors still represent the gold standard in detecting γ radiation for energies ranging from approximately 100 keV to 10 MeV. The combination of high-efficiency and excellent energy resolution and many recent technological developments have significantly increased the range of applications for Ge detectors. We review the state of the art in the fabrication and operation of Ge detectors by mapping recent developments in Ge detector technologies to a range of applications. These include research in nuclear physics, fundamental physics, and astrophysics, as well as applications in medical imaging and homeland security. Ge detector technologies will remain vitally important for applied and basic research instruments for high-sensitivity γ-ray detection in the future.

We review the theoretical status of b → s hadronic penguin decays in the Standard Model and beyond. We summarize the main theoretical tools to compute branching ratios and CP asymmetries for b → s penguin-dominated nonleptonic decays and discuss the theoretical uncertainties in the prediction of time-dependent CP asymmetries in these processes. We consider general aspects of b → s transitions beyond the Standard Model. Then we present detailed predictions in supersymmetric models with new sources of flavor and CP violation.

Few would dispute that the science of particle physics in the United States has reached a crossroads. Policies, decisions, and events of the coming decade will be critical in determining whether the United States continues to carry out a competitive program of leadership in this field of fundamental science. The field of particle physics has responded to this reality by fundamentally changing its model of communication from “business as usual” to a strategic and collaborative method that is clearly focused on achieving a healthy future for the science. Over the past half-dozen years, the particle physics community has gone from being an oft-cited example of how not to communicate effectively, to a frequently cited—and emulated—model for science communication. This review outlines the new approach toward communication in particle physics and then goes into detail about three case studies.

Primordial nucleosynthesis probes the Universe during its early evolution. Given the progress in exploring the constituents, structure, and recent evolution of the Universe, it is timely to review the status of Big Bang Nucleosynthesis (BBN) and confront its predictions, and the constraints that emerge from them, with those derived from independent observations of the Universe at much later epochs. Following an overview of the key physics that controls the synthesis of the elements in the early Universe, the predictions of BBN in the standard (and some nonstandard) models of cosmology and particle physics are presented. The observational data used to infer the primordial abundances are described, with an emphasis on the distinction between precision and accuracy. These are compared with the predictions, testing the internal consistency of BBN and enabling a comparison of the BBN-inferred constraints with those derived from the cosmic microwave background radiation and large scale structure data.