51844539
Partons in phase space
Within QED, we examine several issues related to constructing a parton-model-based QCD transport theory. We rewrite the QED analog of the parton model, the Weizsaecker-Williams Approximation, entirely in terms of phase-space quantities and we study the phase-space photon and electron densities created by a classical point charge. We find that the densities take a distinctive ``source-propagator'' form. This form does not arise in a conventional derivation of the semiclassical transport equations because of the overuse of the gradient approximation. We do not apply the gradient approximation and so derive the phase-space analog of the Generalized Fluctuation-Dissipation Theorem. Together, this theorem and the expression for the phase-space particle self-energies give a set of coupled phase-space evolution equations. We illustrate how these evolution equations can be used perturbatively or to derive semiclassical transport equations. Our work relies on phase-space propagators and sources, so we describe them in detail when calculating the photon and electron phase-space densities. We use these tools to discuss the shape of a nucleon's parton cloud.
14160182
Proposal for a High Energy Nuclear Database
We propose to develop a high-energy heavy-ion experimental database and make it accessible to the scientific community through an on-line interface. This database will be searchable and cross-indexed with relevant publications, including published detector descriptions. Since this database will be a community resource, it requires the high-energy nuclear physics community's financial and manpower support. This database should eventually contain all published data from Bevalac and AGS to RHIC to CERN-LHC energies, proton-proton to nucleus-nucleus collisions as well as other relevant systems, and all measured observables. Such a database would have tremendous scientific payoff as it makes systematic studies easier and allows simpler benchmarking of theoretical models to a broad range of old and new experiments. Furthermore, there is a growing need for compilations of high-energy nuclear data for applications including stockpile stewardship, technology development for inertial confinement fusion and target and source development for upcoming facilities such as the Next Linear Collider. To enhance the utility of this database, we propose periodically performing evaluations of the data and summarizing the results in topical reviews.
18546888
A high-energy nuclear database proposal
We propose to develop a high-energy heavy-ion experimental database and make it accessible to the scientific community through an on-line interface. This database will be searchable and cross-indexed with relevant publications, including published detector descriptions. Since this database will be a community resource, it requires the high-energy nuclear physics community’s financial and manpower support. This database should eventually contain all published data from the Bevalac, AGS and SPS to RHIC and LHC energies, proton-proton to nucleus-nucleus collisions as well as other relevant systems, and all measured observables. Such a database would have tremendous scientific payoff as it makes systematic studies easier and allows simpler benchmarking of theoretical models to a broad range of old and new experiments. Furthermore, there is a growing need for compilations of high-energy nuclear data for applications including stockpile stewardship, technology development for inertial confinement fusion and target and source development for upcoming facilities such as the Next Linear Collider. To enhance the utility of this database, we propose periodically performing evaluations of the data and summarizing the results in topical reviews.
118647623
Efficient and robust calculation of femtoscopic correlation functions in spherical harmonics directly from the raw pairs measured in heavy-ion collisions
We present the formalism for calculating the femtoscopic correlation function directly in spherical harmonics. The numerator and denominator are stored as a set of one-dimensional histograms representing the spherical harmonic decompositions of each. We present the formalism to calculate the correlation function from them directly, without going to any three-dimensional histogram. We discuss the practical implementation of the method and we provide an example of its use. We also discuss the stability of the method in the presence of angular holes in the underlying data (e.g., from experimental acceptance)
15329980
Optimized discretization of sources imaged in heavy-ion reactions
We develop the new method of optimized discretization for imaging the relative source from two particle correlation functions. In this method, the source resolution depends on the relative particle separation and is adjusted to available data and their errors. We test the method by restoring assumed pp sources and then apply the method to pp and IMF data. In reactions below 100 MeV/nucleon, significant portions of the sources extend to large distances (r > 20 fm). The results from the imaging show the inadequacy of common Gaussian source-parametrizations. We establish a simple relation between the height of the pp correlation function and the source value at short distances, and between the height and the proton freeze-out phase-space density.
120407877
HEND: A DATABASE FOR HIGH-ENERGY NUCLEAR DATA
We propose to develop a high-energy heavy-ion experimental database and make it accessible to the scientific community through an on-line interface. The database will be searchable and cross-indexed with relevant publications, including published detector descriptions. It should eventually contain all published data from older heavy-ion programs such as the Bevalac, AGS, SPS and FNAL fixed-target programs, as well as published data from current programs at RHIC and new facilities at GSI (FAIR), KEK/Tsukuba and the LHC collider. This data includes all proton-proton, proton-nucleus to nucleus-nucleus collisions as well as other relevant systems and all measured observables. Such a database would have tremendous scientific payoff as it makes systematic studies easier and allows simpler benchmarking of theoretical models to a broad range of experiments. To enhance the utility of the database, we propose periodic data evaluations and topical reviews. These reviews would provide an alternative and impartial mechanism to resolve discrepancies between published data from rival experiments and between theory and experiment. Since this database will be a community resource, it requires the high-energy nuclear physics community's financial and manpower support.
6269112
Action functionals for relativistic perfect fluids
Action functionals describing relativistic perfect fluids are presented. Two of these actions apply to fluids whose equations of state are specified by giving the fluid energy density as a function of particle number density and entropy per particle. Other actions apply to fluids whose equations of state are specified in terms of other choices of dependent and independent fluid variables. Particular cases include actions for isentropic fluids and pressureless dust. The canonical Hamiltonian forms of these actions are derived, symmetries and conserved charges are identified, and the boundary value and initial value problems are discussed. As in previous works on perfect fluid actions, the action functionals considered depend on certain Lagrange multipliers and Lagrangian coordinate fields. Particular attention is paid to the interpretations of these variables and to their relationships to the physical properties of the fluid.
119440102
Conformal invariance and the conformal-traceless decomposition of the gravitational field
Einstein’s theory of general relativity is written in terms of the variables obtained from a conformaltraceless decomposition of the spatial metric and extrinsic curvature. The determinant of the conformal metric is not restricted, so the action functional and equations of motion are invariant under conformal transformations. With this approach the conformal-traceless variables remain free of density weights. The conformal invariance of the equations of motion can be broken by imposing an evolution equation for the determinant of the conformal metric g. Two conditions are considered, one in which g is constant in time and one in which g is constant along the unit normal to the spacelike hypersurfaces. This approach is used to write the Baumgarte-Shapiro-Shibata-Nakamura system of evolution equations in conformally invariant form. The presentation includes a discussion of the conformal thin sandwich construction of gravitational initial data, and the conformal flatness condition as an approximation to the evolution equations.
124330538
Giant resonances observed in the scattering of 96- and 115-MeV alpha particles
Beams of 96- and 115-MeV $alpha$ particles were used to study the giant resonance region in 27 nuclei ranging from $sup 14$N to $sup 208$Pb. A prominent broad (GAMMA=3--7 MeV) peak is present in the spectra at an excitation energy of approx.63/A$sup 1$/$sup 3$ MeV for all nuclei studied with A> or =36. No such prominent peak is apparent for A<32. The angular distributions of the peak are characterized by an oscillatory behavior which is quite different from the monotonic behavior of the background. Distorted wave calculations with L=2 reproduce the experimental angular distributions quite well for most of the nuclei. Energy-weighted sum rule fractions range from 30--50% for the lighter targets to near 100% for the heavier targets. Distorted wave calculations with a breathing mode (L=0) form factor fail to reproduce the observed resonance strength by about a factor of 3 for all targets. The width of the peak is smallest for the closed shell nuclei $sup 40$Ca, $sup 90$Zr, $sup 144$Sm, and $sup 208$Pb. A small but significant broadening is observed in the rare-earth region of deformed nuclei. The giant dipole resonance is not appreciably excited for any of the targets. (AIP)
1576896
Comparison of high-accuracy numerical simulations of black-hole binaries with stationary-phase post-Newtonian template waveforms for initial and advanced LIGO
We study the effectiveness of stationary-phase approximated post-Newtonian waveforms currently used by ground-based gravitational-wave detectors to search for the coalescence of binary black holes by comparing them to an accurate waveform obtained from numerical simulation of an equal-mass non-spinning binary black hole inspiral, merger and ringdown. We perform this study for the initial- and advanced-LIGO detectors. We find that overlaps between the templates and signal can be improved by integrating the match filter to higher frequencies than used currently. We propose simple analytic frequency cutoffs for both initial and advanced LIGO, which achieve nearly optimal matches, and can easily be extended to unequal-mass, spinning systems. We also find that templates that include terms in the phase evolution up to 3.5 post-Newtonian (pN) order are nearly always better, and rarely significantly worse, than 2.0 pN templates currently in use. For initial LIGO we recommend a strategy using templates that include a recently introduced pseudo-4.0 pN term in the low-mass (M ≤ 35 M☉) region, and 3.5 pN templates allowing unphysical values of the symmetric reduced mass η above this. This strategy always achieves overlaps within 0.3% of the optimum, for the data used here. For advanced LIGO we recommend a strategy using 3.5 pN templates up to M = 12 M☉, 2.0 pN templates up to M = 21 M☉, pseudo-4.0 pN templates up to 65 M☉, and 3.5 pN templates with unphysical η for higher masses. This strategy always achieves overlaps within 0.7% of the optimum for advanced LIGO.
119298185
BSSN in spherical symmetry
The BSSN (Baumgarte?Shapiro?Shibata?Nakamura) formulation of the Einstein evolution equations is written in spherical symmetry. These equations can be used to address a number of technical and conceptual issues in numerical relativity in the context of a single Schwarzschild black hole. One of the benefits of spherical symmetry is that the numerical grid points can be tracked on a Kruskal?Szekeres diagram. Boundary conditions suitable for puncture evolution of a Schwarzschild black hole are presented. Several results are shown for puncture evolution using a fourth-order finite difference implementation of the equations.