Showing papers in "Annual Review of Nuclear and Particle Science in 2012"
TL;DR: The neutrino-heating mechanism, aided by nonradial flows, drives explosions, albeit low-energy ones, of O-Ne-Mg-core and some Fe-core progenitors as mentioned in this paper.
Abstract: Supernova theory, numerical and analytic, has made remarkable progress in the past decade. This progress was made possible by more sophisticated simulation tools, especially for neutrino transport, improved microphysics, and deeper insights into the role of hydrodynamic instabilities. Violent, large-scale nonradial mass motions are generic in supernova cores. The neutrino-heating mechanism, aided by nonradial flows, drives explosions, albeit low-energy ones, of O-Ne-Mg-core and some Fe-core progenitors. The characteristics of the neutrino emission from newborn neutron stars were revised, new features of the gravitational-wave signals were discovered, our notion of supernova nucleosynthesis was shattered, and our understanding of pulsar kicks and explosion asymmetries was significantly improved. But simulations also suggest that neutrino-powered explosions might not explain the most energetic supernovae and hypernovae, which seem to demand magnetorotational driving. Now that modeling is being advanced from...
971 citations
TL;DR: In this article, an ensemble of mass and radius observations can realistically restrict the properties of dense matter and, in particular, the behavior of the nuclear symmetry energy near the nuclear saturation density.
Abstract: Neutron stars are valuable laboratories for the study of dense matter. Recent observations have uncovered both massive and low-mass neutron stars and have also set constraints on neutron star radii. The largest mass measurements are powerfully influencing the high-density equation of state because of the existence of the neutron star maximum mass. The smallest mass measurements, and the distributions of masses, have implications for the progenitors and formation mechanisms of neutron stars. The ensemble of mass and radius observations can realistically restrict the properties of dense matter and, in particular, the behavior of the nuclear symmetry energy near the nuclear saturation density. Simultaneously, various nuclear experiments are progressively restricting the ranges of parameters describing the symmetry properties of the nuclear equation of state. In addition, new theoretical studies of pure neutron matter are providing insights. These observational, experimental, and theoretical constraints of dense matter, when combined, are now revealing a remarkable convergence.
825 citations
TL;DR: The Large Hadron Collider (LHC) at CERN started operation with heavy-ion beams, colliding lead nuclei at a center-of-mass energy of 2.76 TeV per nucleon as discussed by the authors.
Abstract: At the end of 2010, the Large Hadron Collider (LHC) at CERN started operation with heavy-ion beams, colliding lead nuclei at a center-of-mass energy of 2.76 TeV per nucleon. These collisions ushere...
382 citations
TL;DR: A core-collapse supernova will produce an enormous burst of neutrinos of all flavors in the few-tens-of-MeV range as mentioned in this paper, which will yield answers to many physics and astrophysics questions.
Abstract: A core-collapse supernova will produce an enormous burst of neutrinos of all flavors in the few-tens-of-MeV range. Measurement of the flavor, time, and energy structure of a nearby core-collapse neutrino burst will yield answers to many physics and astrophysics questions. The neutrinos left over from past cosmic supernovae are also observable, and their detection will improve knowledge of core-collapse rates and average neutrino emission. This review describes experimental techniques for detection of core-collapse neutrinos, as well as the sensitivities of current and future detectors.
228 citations
TL;DR: In this article, the authors review the effect of the formation of nonlinear structures on the expansion rate, spatial curvature, and light propagation in the universe, focusing on the possibility that this effect could explain cosmological observations without requiring the introduction of dark energy or modified gravity.
Abstract: We review the effect of the formation of nonlinear structures on the expansion rate, spatial curvature, and light propagation in the universe, focusing on the possibility that this effect could explain cosmological observations without requiring the introduction of dark energy or modified gravity. We concentrate on explaining the relevant physics and highlighting open questions.
228 citations
TL;DR: In this article, the status of the theoretical and experimental determinations of the muon magnetic moment anomaly is reviewed, as well as the implications for physics beyond the Standard Model that come from past and future experiments.
Abstract: We review the status of the theoretical and experimental determinations of the muon magnetic moment anomaly. We discuss future experimental efforts, as well as implications for physics beyond the Standard Model that come from past and future experiments.
144 citations
TL;DR: In this paper, the chiral effective field theory of nuclear forces and atomic nuclei is introduced and the status of the nuclear Hamiltonian derived in this framework and some recent applications in few-nucleon sys- tems.
Abstract: This review briefly introduces the chiral effective field theory of nuclear forces and atomic nuclei. We discuss the status of the nuclear Hamiltonian derived in this framework and some recent applications in few-nucleon sys- tems. We also introduce nuclear lattice simulations as a new tool to address the many-body problem and present some of the first results based on that method.
86 citations
TL;DR: In this paper, the authors review the methods developed for combining the parton shower approximation to quantum chromodynamics with fixed-order perturbation theory so as to achieve next-to-leading-order (NLO) accuracy for inclusive observables.
Abstract: We review the methods developed for combining the parton shower approximation to quantum chromodynamics with fixed-order perturbation theory so as to achieve next-to-leading-order (NLO) accuracy for inclusive observables. These developments have made it possible to generate fully simulated hadronic final states with the precision and stability of NLO calculations. We explain the underlying theory of the existing methods, MC@NLO and POWHEG, together with their similarities, differences, achievements, and limitations. For illustration, we mainly compare results on Higgs boson production at the LHC, with particular emphasis on the residual uncertainties arising from the different treatment of effects beyond NLO. We also briefly summarize the difference between these NLO plus parton shower methods and matrix-element plus parton shower matching, along with current efforts to combine the two approaches.
82 citations
TL;DR: A review of results in this regime that have been established with lattice gauge theory, directly from the QCD Lagrangian can be found in this article, which is a good starting point for this paper.
Abstract: Quantum chromodynamics (QCD) reduces the strong interactions, in all their variety, to an elegant 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 paper reviews a variety of results in this regime that have been established with lattice gauge theory, directly from the QCD Lagrangian. This body of work sheds light on the origin of hadron masses, its interplay with dynamical symmetry breaking, as well as on other intriguing features such as the phase structure of QCD. In addition, 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.
77 citations
TL;DR: A comprehensive program of experiments has been performed at three accelerator laboratories to determine the role of strange quarks in the electromagnetic form factors of the nucleon as discussed by the authors, and the remarkable technical progress associated with this program, describes the various methods used in the different experiments, and summarizes the physics results along with recent theoretical calculations.
Abstract: Measurements of the neutral weak-vector form factors of the nucleon provide unique access to the strange quark content of the nucleon. These form factors can be studied by using parity-violating electron scattering. A comprehensive program of experiments has been performed at three accelerator laboratories to determine the role of strange quarks in the electromagnetic form factors of the nucleon. This article reviews the remarkable technical progress associated with this program, describes the various methods used in the different experiments, and summarizes the physics results along with recent theoretical calculations.
65 citations
TL;DR: In this article, the authors review some outstanding puzzles and experimental anomalies in hadron physics that appear to challenge conventional wisdom and, in some cases, the foundations of quantum chromodynamics (QCD), and propose new tests and experiments that could illuminate the underlying physics and novel phenomenological features of QCD.
Abstract: We review some outstanding puzzles and experimental anomalies in hadron physics that appear to challenge conventional wisdom and, in some cases, the foundations of quantum chromodynamics (QCD). We also discuss possible solutions and propose new tests and experiments that could illuminate the underlying physics and novel phenomenological features of QCD. In some cases, new perspectives for QCD physics have emerged.
TL;DR: The Casimir force, predicted to exist more than half a century ago, remains at the forefront of modern physics with broad applications beyond the originally predicted attraction of uncharged plates as discussed by the authors.
Abstract: The Casimir force, predicted to exist more than half a century ago, remains at the forefront of modern physics with broad applications beyond the originally predicted attraction of uncharged plates. This review discusses recent issues, particularly the finite temperature correction and its resolution, along with limits on new long-range forces that can arise in the context of, for example, string theory. A meta-review of books and reviews is also presented.
TL;DR: The history of electron spin is summarized in this paper, which includes the discovery of the electron spin, the birth of quantum electrodynamics, the invention of magnetic resonance, the renormalization, the anomalous magnetic moment of electron in experiment and theory, and searches for the electron electric dipole moment.
Abstract: The history of electron spin is summarized. Topics include the discovery of electron spin, the birth of quantum electrodynamics, the invention of magnetic resonance, the invention of renormalization, the anomalous magnetic moment of the electron in experiment and theory, and searches for the electron electric dipole moment.
TL;DR: In this article, the authors discuss the construction of maximally supersymmetric gauge theories that arise on the world-volume branes in string theory and M-theory, and briefly discuss the six-dimensional conformal field theory that is expected to arise on M5-branes.
Abstract: In this informal review for nonspecialists, we discuss the construction of maximally supersymmetric gauge theories that arise on the world-volume branes in string theory and M-theory. We focus on the relatively recent construction of M2-brane world-volume theories. In a formal sense, the existence of these quantum field theories can be viewed as predictions of M-theory. Their construction is therefore a reinforcement of the ideas underlying string theory and M-theory. We also briefly discuss the six-dimensional conformal field theory that is expected to arise on M5-branes. The construction of this theory is not only an important open problem for M-theory but also a significant challenge to our current understanding of quantum field theory more generally.
TL;DR: In this paper, the authors surveyed general classes of mechanisms for generating small neutrino masses from a top-down (superstring) perspective, including Dirac masses, Majorana masses via the Weinberg operator, and Majorana mass from a seesaw mechanism.
Abstract: General classes of mechanisms for generating small neutrino masses are surveyed from a top-down (superstring) perspective. In particular, string constructions have motivated various possibilities involving higher-dimensional operators, string instantons, and wave-function overlaps in large or warped extra dimensions. These constructions may yield small Dirac masses, Majorana masses via the Weinberg operator, or Majorana masses from a seesaw mechanism, although the last typically differ in detail from the more conventional Grand Unified Theory models. Possibilities for mixing between light, active neutrinos and sterile neutrinos are surveyed.
TL;DR: In this paper, the authors review studies of the underlying event (UE) in hadronic collisions, dating from the first CDF studies in 2000 to the latest LHC findings and surprises.
Abstract: I review studies of the underlying event (UE) in hadronic collisions, dating from the first CDF studies in 2000 to the latest LHC findings and surprises. I explain the CDF quantum chromodynamics (QCD) Monte Carlo model tunes and describe how well the Tevatron tunes did at predicting the behavior of the UE at the LHC. In a very short time, the LHC experiments collected a large amount of data at 900 GeV and 7 TeV that can be used to study the UE in great detail. I review the LHC UE results and compare them with one another, with the Tevatron results, and with some of the LHC QCD Monte Carlo model tunes. I also explain the relationship between minimum bias collisions and the UE and discuss new techniques for studying the UE (i.e., techniques beyond the traditional approach).
TL;DR: The measurement of hard scattering processes, meaning those with energy scales of more than a few GeV, is the main method by which physics is being explored and extended by the experiments at the Large Hadron Collider as mentioned in this paper.
Abstract: The measurement of hard scattering processes, meaning those with energy scales of more than a few GeV, is the main method by which physics is being explored and extended by the experiments at the Large Hadron Collider. We review the principal measurements made so far and explain what they have told us about physics at the energy frontier.
TL;DR: In this paper, the status of the CLIC (Compact Linear Collider) study toward feasibility demonstration of a novel and challenging technology that has been specially developed to extend the energy reach of linear colliders into the multi-TeV range so that they will be complementary to the LHC (Large Hadron Collider).
Abstract: This article reviews the status of the CLIC (Compact Linear Collider) study toward feasibility demonstration of a novel and challenging technology that has been specially developed to extend the energy reach of linear colliders into the multi-TeV range so that they will be complementary to the LHC (Large Hadron Collider). A conceptual design report is being prepared; it summarizes the performance of a high-energy facility based on this technology, as well as the results of the research and development carried out to address its feasibility.
TL;DR: Borexino as discussed by the authors is a low-background liquid scintillation detector currently acquiring solar and terrestrial neutrino data at the Gran Sasso underground laboratory in Italy, which has produced measurements of 7Be, 8B, and pep solar neutrinos, as well as measurements of terrestrial and long-baseline reactor antineutrinos.
Abstract: Borexino is a low-background liquid scintillation detector currently acquiring solar and terrestrial neutrino data at the Gran Sasso underground laboratory in Italy. Since the start of operations in 2007, Borexino has produced measurements of 7Be, 8B, and pep solar neutrinos, as well as measurements of terrestrial and long-baseline reactor antineutrinos. The measurements were made possible by the development of low-background scintillator spectroscopy that enabled direct detection of sub-MeV solar neutrinos. The general design features of the detector are described together with current results and prospects for future measurements.