122995373
Quantum dynamics, the RHIC HBT puzzle, and the chiral phase transition
We use a relativistic optical model formalism to describe the emission of pions produced within a dense, strongly-interacting system of matter in the presence of strong radial flow and absorption. The attenuated or unattenuated plane waves of earlier emission function approaches are replaced with “distorted wave” solutions to a relativistic wave equation including a complex optical potential. The resulting distorted-wave emission function model (DWEF) is used in numerical calculations to describe HBT correlations and the resonance-corrected pion spectrum from central-collision STAR Au+Au pion data at s = 200  GeV . The parameters of the emission function are constrained by adopting a pion formation temperature taken from lattice gauge calculations and a chemical potential equal to the pion mass suggested by chiral symmetry restoration. The optical has strong attraction as well as absorption. Excellent agreement with the STAR data are obtained. The applications are extended by applying linear participant scaling to the space-time parameters of the model, so that we predict HBT radii over a range of centralities for both Au+Au and Cu+Cu collisions. Good agreement is found with STAR HBT data for all but the most peripheral collisions. For outgoing pion momenta less than about 500 MeV/c, our pionic distorted wave functions are very different than the corresponding functions obtained by using the familiar eikonal approximation. All of the results presented in the talk are in Refs. [J.G. Cramer, G.A. Miller, J.M.S. Wu and J.H.S. Yoon, Phys. Rev. Lett. 94 (2005) 102302 arXiv:nucl-th/0411031 ], [G.A. Miller and J.G. Cramer, Polishing the lens. I: Pionic final state interactions and HBT correlations. Distorted wave emission function (DWEF) formalism and examples, arXiv:nucl-th/0507004 , submitted to Phys. Rev. C].
119513589
Shapes of the proton
A model proton wave function, constructed using Poincar\'e invariance and constrained by recent electromagnetic form factor data, is used to study the shape of the proton. Spin-dependent quark densities are defined as matrix elements of density operators in proton states of definite polarization, and shown to have an infinite variety of nonspherical shapes. For high momentum quarks with spin parallel to that of the proton, the shape resembles that of a peanut, but for quarks with antiparallel spin the shape is that of a bagel.
356245
Current algebra and the cloudy-bag model.
Two versions of the cloudy-bag model (surface and volume coupling) satisfy the commutation relations of current algebra. Perturbation-theory evaluations of various observables are compared for the two treatments. The electromagnetic properties are essentially the same in both versions. The volume-coupling model contains, in lowest order, a pion-quark contact interaction that contributes to the axial-vector current. Including the effect of this term leads to a computed value of g/sub A/ of about 1.25, if the radius of the nucleon bag is around 1.0 fm.
122904929
Isobar dynamics and pion-nucleus elastic scattering
Abstract A new formalism is developed for studying pion-nucleus scattering in a model which takes into account the dynamics of the (3, 3) pion-nucleon resonance, or Δ isobar. This treatment is used to calculate π + elastic scattering from 16 O, 40 Ca, 48 Ca and 208 Pb at energies from 114 to 240 MeV. Some results for π − elastic scattering are also given. From fits to π + scattering data it is found that the Δ-nucleus interaction is well described by a spherical local complex potential proportional to the nuclear density. The central strength of this potential depends on energy but not on nuclear mass number. Some difficulties in determining the parameters of this potential from elastic scattering are discussed.
120464871
Deuteron photodisintegration: Impulse approximation and gauge invariance
We study the question of whether calculations of deuteron photodisintegration respect gauge invariance, and show that the impulse approximation is in severe disagreement with gauge invariance. The method in which Siegert's theorem is implemented is consistent with gauge invariance to within ten percent. We introduce a modification of the impulse approximation in which the current is conserved exactly. For deuteron photodisintegration this method yields essentially the same results as that of Partovi. Our method can easily be applied to electron- or neutrino-nucleus scattering.
118854850
Polarized quark distributions in nuclear matter
We compute the polarized quark distribution function of a bound nucleon. The chiral quark-soliton model provides the quark and antiquark substructure of the nucleon embedded in nuclear matter. Nuclear effects cause significant modifications to the polarized distributions, including an enhancement of the axial coupling constant.
111136184
An Improved Control System for Van De Graaff Accelerators
In an effort to improve the energy stability and operating convenience of the Rutgers-Bell FN Tandem, a study has been made of the processes involved in the standard Van de Graaff corona stabilization system. In the light of these observations, a terminal voltage control system has been designed using error signals derived both from the slit system and the capacity pickoff plates. The system operates using either the standard slit system, or the machines' Generating Voltmeter as the terminal voltage reference, switching automatically to the G. V. system when beam is lost for any reason.
119233886
On the origin of gravitational Lorentz covariance
We provide evidence that general relativity (GR) is the unique spatially covariant effective field theory of the transverse, traceless graviton degrees of freedom. The Lorentz covariance of GR, having not been assumed in our analysis, is thus plausibly interpreted as an accidental or emergent symmetry of the gravitational sector.
121623246
Semiconductor Particle Detectors
The operation, properties, and fabrication of semiconductor detectors are reviewed. Materials other than Ge and Si are mentioned only briefly. The electronics involved in use of semiconductors as particle detectors is discussed. Application and possible applications to the following are summarized: nuclear reaction chargedparticle spectroscopy, particle identification, mosaics and special structures, alpha -particle spectroscopy, fission studies, neutron spectroscopy, BETA spectroscopy, gamma spectroscopy, detection of minimum- ionizing particles, low-temperature physics, space vehicles, industry, and medicine.