Annual Review of Nuclear and Particle Science - Volume 50, 2000
Volume 50, 2000
- Preface
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- Review Articles
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The Shears Mechanism in Nuclei1
Vol. 50 (2000), pp. 1–36More Less▪ AbstractThis chapter reviews the experimental properties of shears bands. The most puzzling characteristic of these structures is the emergence of rotational-like behavior while the nucleus retains a small quadrupole deformation. Regardless of the details of particular theoretical models, it can be shown that the most important degree of freedom in describing the shears mechanism is the shears angle. It is then possible to develop a semiclassical description of the shears mechanism, in which the nature (multipole order) of the interaction between valence protons and neutrons constituting the shears “blades” may be derived and the dynamics of the system described. We discuss the competition between the shears mechanism and collective rotation and mention the connection to “magnetic rotation.” Directions for future theoretical and experimental efforts are suggested.
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Energy Loss in Perturbative QCD
R. Baier, D. Schiff, and B. G. ZakharovVol. 50 (2000), pp. 37–69More Less▪ AbstractWe review the propagation of energetic partons in hot or cold QCD matter, as known from recent work. We summarize advances in the understanding of both collisional and radiative energy loss. Our emphasis is on radiative energy loss, which has very interesting properties that may help to detect the quark-gluon plasma produced in heavy-ion collisions. We describe two different theoretical approaches, which lead to the same radiated gluon energy spectrum. The case of a longitudinally expanding QCD plasma is investigated. The energy lost by a jet with given opening angle is calculated with the aim of making predictions for the suppression (quenching) of hard jet production. Phenomenological implications for the difference between hot and cold matter are discussed. Numerical estimates of the loss suggest that it may be significantly greater in hot matter than in cold. This makes the magnitude of the radiative energy loss a remarkable signal for quark-gluon plasma formation.
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The CDF and DØ Upgrades for Run II
T. LeCompte, and H. T. DiehlVol. 50 (2000), pp. 71–177More Less▪ AbstractThe DØ and CDF collaborations are preparing their detectors for the Tevatron Run II. A 20-fold increase in integrated luminosity is planned for the first two years of the upcoming run, and the detector subsystems are undergoing substantial improvements to handle the higher rates as well as to better measure the products of the
, interactions. This review discusses the physics goals that motivate these detector enhancements and describes in detail the improvements being made to the charged particle tracking, calorimetry, muon identification, and trigger subsystems of both detectors.
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Precision Nuclear Measurements with Ion Traps1
Vol. 50 (2000), pp. 119–152More Less▪ AbstractProperties of charged particles confined in ion traps can be determined to high accuracy. The ability to capture stable and unstable isotopes in such traps with high efficiency has led to a series of measurements of gross properties of nuclei. These recent high-accuracy measurements, along with the enabling technological developments and propects for the field, are presented.
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The Quantum Physics of Black Holes: Results from String Theory
Vol. 50 (2000), pp. 153–206More Less▪ AbstractWe review recent progress in our understanding of the physics of black holes. In particular, we discuss the ideas from string theory that explain the entropy of black holes from a counting of microstates of the hole, and the related derivation of unitary Hawking radiation from such holes.
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Precision Measurements of the W Boson Mass
Vol. 50 (2000), pp. 207–248More Less▪ AbstractThe standard model of electroweak interactions has had great success in describing the observed data over the past three decades. The precision of experimental measurements affords tests of the standard model at the quantum loop level beyond leading order. Despite this success, it is important to continue confronting experimental measurements with the standard model's predictions because any deviation would signal new physics. As a fundamental parameter of the standard model, the mass of the W boson, MW, is of particular importance. Aside from being an important test of the model itself, a precision measurement of MW can be used to constrain the mass of the Higgs boson, MH. In this article, we review the principal experimental techniques for determining MW and discuss their combination into a single precision MW measurement. We conclude by briefly discussing future prospects for precision measurements of the W boson mass.
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Developments in Rare Kaon Decay Physics
A.R. Barker, and S.H. KettellVol. 50 (2000), pp. 249–297More Less▪ AbstractWe review the current status of the field of rare kaon decays. The study of rare kaon decays has played a key role in the development of the standard model, and the field continues to have significant impact. The two areas of greatest import are the search for physics beyond the standard model and the determination of fundamental standard-model parameters. Due to the exquisite sensitivity of rare kaon decay experiments, searches for new physics can probe very high mass scales. Studies of the K → π ν
modes in particular, where the first event has recently been seen, will permit tests of the standard-model picture of quark mixing and CP violation.
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Strangeness Production in Heavy-Ion Collisions
Vol. 50 (2000), pp. 299–342More Less▪ AbstractStrangeness production is a very useful diagnostic tool in finding the quark-gluon plasma. We review its uses in understanding relativistic heavy-ion collisions. A brief introduction to the main theoretical tools used in interpreting strangeness production is given, and the experimental methods used to extract the signals are discussed in detail. The experimental results from the Brookhaven AGS and CERN SPS programs are presented. We discuss the interpretation of these results, emphasizing their role in the discovery of deconfined quark matter at CERN. Future experiments at RHIC and at the CERN LHC are described.
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Random Matrix Theory and Chiral Symmetry in QCD
Vol. 50 (2000), pp. 343–410More Less▪ AbstractRandom matrix theory is a powerful way to describe universal correlations of eigenvalues of complex systems. It also may serve as a schematic model for disorder in quantum systems. In this review, we discuss both types of applications of chiral random matrix theory to the QCD partition function. We show that constraints imposed by chiral symmetry and its spontaneous breaking determine the structure of low-energy effective partition functions for the Dirac spectrum. We thus derive exact results for the low-lying eigenvalues of the QCD Dirac operator. We argue that the statistical properties of these eigenvalues are universal and can be described by a random matrix theory with the global symmetries of the QCD partition function. The total number of such eigenvalues increases with the square root of the Euclidean four-volume. The spectral density for larger eigenvalues (but still well below a typical hadronic mass scale) also follows from the same low-energy effective partition function. The validity of the random matrix approach has been confirmed by many lattice QCD simulations in a wide parameter range. Stimulated by the success of the chiral random matrix theory in the description of universal properties of the Dirac eigenvalues, the random matrix model is extended to nonzero temperature and chemical potential. In this way we obtain qualitative results for the QCD phase diagram and the spectrum of the QCD Dirac operator. We discuss the nature of the quenched approximation and analyze quenched Dirac spectra at nonzero baryon density in terms of an effective partition function. Relations with other fields are also discussed.
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On the Production of Superheavy Elements
Vol. 50 (2000), pp. 411–479More Less▪ AbstractIn the first century of nuclear physics, 31 radioactive elements were added to the periodic system of elements. In 1996, at GSI, element 112 was synthesized by fusion of 70Zn with 208Pb, and its atomic number was established by a decay chain linked to known isotopes. Relativistic mean field calculations of the ground-state stability of nuclei predict the next spherical proton shell not as previously assumed at Z = 114 but at Z = 120 for 304184120. Moreover, a region of spherical nuclei with depleted central density is predicted at N = 172 for 292172120 by mean field calculations. New elements are established today using recoil separators combined with decay-chain analysis. Three new elements, Z = 110–112, and 18 transactinide isotopes have been discovered since 1985, all assigned by genetical linkage to known isotopes. The production cross sections decrease exponentially going to higher elements and now have reached the 1-pb limit. Fusion aiming at higher and higher atomic numbers is a self-terminated process because of constantly increasing disruptive Coulomb forces. The limitations in the formation and deexcitation stages are presented. The rapid drop to smaller cross sections (“Coulomb falls”) is modified by nuclear structure not only in the ground state of the final product (superheavy element) but also in the collision partners and during the amalgamation process (closed shells and clusters). The prospects to produce higher elements and new isotopes by extrapolating the physics learned from reaching Z = 112 are 283114, which might be found in 76Ge/208Pb at a level of 0.1 pb and linked to 259No. At this level, about 30 transactinide isotopes are still in reach. To explain the stabilization of production cross sections in the pb range claimed in 1999 experiments, new physics delaying the descent in the “Coulomb falls” is to appear. For the FLNR experiments claiming Z = 114, no explanation is offered. For the LBL experiment claiming Z = 118, an explanation from new physics is presented. All experiments need confirmation. Verifying the centrally depleted, spherical nuclei around 292172120 would be a victory for nuclear structure physics, much more interesting than the trivial case of another doubly closed shell nucleus.
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Recent Progress in Neutron Star Theory
Vol. 50 (2000), pp. 481–524More Less▪ AbstractWe review recent progress in the theory of neutron stars and compare its predictions with the observational data on masses, radii, and temperatures. The theory of neutron stars made up of neutrons, protons, and leptons is discussed in detail along with recent models of nuclear forces and modern many-body techniques. The possibilities of pion and kaon condensation in dense neutron star matter are considered, as is the possible occurrence of strange hyperons and quark-matter drops in the stellar core. The structure of mixed-phase matter in neutron stars, as well as the probable effect of phase transitions on the spin down of pulsars, is also discussed.
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Prospects for Spin Physics at RHIC
Vol. 50 (2000), pp. 525–575More Less▪ AbstractColliding beams of 70% polarized protons at up to
GeV, with high luminosity, L = 2 × 1032 cm−2 sec−1, will represent a new and unique laboratory for studying the proton. RHIC-Spin will be the first polarized-proton collider and will be capable of copious production of jets, directly produced photons, and W and Z bosons. Features will include direct and precise measurements of the polarization of the gluons and of
, u, and d quarks in a polarized proton. Parity violation searches for physics beyond the standard model will be competitive with unpolarized searches at the Fermilab Tevatron. Transverse spin will explore transversity for the first time, as well as quark-gluon correlations in the proton. Spin dependence of the total cross section and in the Coulomb nuclear interference region will be measured at collider energies for the first time. These qualitatively new measurements can be expected to deepen our understanding of the structure of matter and of the strong interaction.
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B Mixing1
Vol. 50 (2000), pp. 577–641More Less▪ AbstractThe neutral B mesons, B0 and Bs0, can oscillate between their particle and antiparticle states owing to flavor-changing weak interactions. In recent years, techniques to detect these oscillations as a function of the meson's decay time have been developed. This article reviews the physics of flavor oscillations and summarizes theoretical predictions. The many observations that demonstrate the time dependence of
oscillations are presented along with a combined measurement of its frequency, Δ md = 0.484 ± 0.015 ps−1. The attempts to measure the Bs0 oscillation frequency, both directly and indirectly, are then summarized, currently resulting in a limit of Δ ms > 14.6 ps−1 (95% CL). Finally, values for the CKM elements |Vtd| = (3.6 ± 0.4) × 10−3 and |Vts/Vtd| > 4.7 (95% CL) are extracted.
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The QCD Coupling Constant1
Vol. 50 (2000), pp. 643–678More Less▪ AbstractThis paper presents a summary of the current status of determinations of the strong coupling constant αs. A detailed description of the definition, scale dependence, and inherent theoretical ambiguities is given. The various physical processes that can be used to determine αs are reviewed and attention is given to the uncertainties, both theoretical and experimental.
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High-Energy Neutrino Astrophysics
Vol. 50 (2000), pp. 679–749More Less▪ AbstractHigh-energy (>100 MeV) neutrino astrophysics enters an era of opportunity and discovery as the sensitivity of detectors approaches astrophysically relevant flux levels. We review the major challenges for this emerging field, among which the nature of dark matter, the origin of cosmic rays, and the physics of extreme objects such as active galactic nuclei, gamma-ray bursts, pulsars, and supernova remnants are of prime importance. Variable sources at cosmological distances allow the probing of neutrino propagation properties over baselines up to about 20 orders of magnitude larger than those probed by terrestrial long-baseline experiments. We review the possible astrophysical sources of high-energy neutrinos, which also act as an irreducible background to searches for phenomena at the electroweak and grand-unified-theory symmetry-breaking scales related to possible supersymmetric dark matter and topological defects. Neutrino astronomy also has the potential to discover previously unimagined high-energy sources invisible in other channels and provides the only means for direct observations of the early universe prior to the era of decoupling of photons and matter. We conclude with a discussion of experimental approaches and a short report on present projects and prospects. We look forward to the day when it will be possible to see the universe through a new window in the light of what may be its most numerous particle, the elusive neutrino.
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Previous Volumes
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Volume 74 (2024)
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Volume 73 (2023)
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Volume 72 (2022)
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Volume 71 (2021)
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Volume 70 (2020)
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Volume 69 (2019)
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Volume 68 (2018)
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Volume 67 (2017)
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Volume 66 (2016)
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Volume 65 (2015)
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Volume 64 (2014)
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Volume 63 (2013)
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Volume 62 (2012)
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Volume 61 (2011)
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Volume 60 (2010)
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Volume 59 (2009)
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Volume 58 (2008)
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Volume 57 (2007)
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Volume 56 (2006)
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Volume 55 (2005)
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Volume 54 (2004)
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Volume 53 (2003)
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Volume 52 (2002)
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Volume 51 (2001)
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Volume 50 (2000)
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Volume 49 (1999)
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Volume 48 (1998)
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Volume 47 (1997)
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Volume 46 (1996)
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Volume 45 (1995)
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Volume 44 (1994)
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Volume 43 (1993)
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Volume 42 (1992)
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Volume 41 (1991)
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Volume 40 (1990)
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Volume 39 (1989)
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Volume 38 (1988)
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Volume 37 (1987)
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Volume 36 (1986)
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Volume 35 (1985)
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Volume 34 (1984)
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Volume 33 (1983)
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Volume 32 (1982)
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Volume 31 (1981)
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Volume 30 (1980)
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Volume 29 (1979)
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Volume 28 (1978)
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Volume 27 (1977)
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Volume 26 (1976)
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Volume 25 (1975)
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Volume 24 (1974)
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Volume 23 (1973)
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Volume 22 (1972)
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Volume 21 (1971)
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Volume 20 (1970)
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Volume 19 (1969)
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Volume 18 (1968)
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Volume 17 (1967)
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Volume 16 (1966)
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Volume 15 (1965)
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Volume 14 (1964)
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Volume 13 (1963)
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Volume 12 (1962)
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Volume 11 (1961)
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Volume 10 (1960)
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Volume 9 (1959)
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Volume 8 (1958)
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Volume 7 (1957)
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Volume 6 (1956)
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Volume 5 (1955)
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Volume 4 (1954)
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Volume 3 (1953)
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Volume 2 (1953)
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Volume 1 (1952)
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Volume 0 (1932)