Session FE - High Energy Nuclear/Particle Physics.
ORAL session, Monday afternoon, November 08
Paris B, Sheraton Chapel Hill

[FE.01] Spinning Particle Motion in a Kerr Geometry

The physics of particle motion in a Kerr geometry has been extensively studied. The case of motion of particles with spin is less well investigated. We have studied the case of the motion of a spinning particle by applying the Papapetrou equation, which includes a spin - curvature coupling term, and an equation that describes the evolution of the spin of the particle. The motion is considered for a Kerr geometry in the weak field limit. We have obtained numerical solutions to this system of equations. Our results suggest that spin orientation is important for particle trajectories in a manner that is similar to the Stern-Gerlach effect. This could be important for the motion of very low mass neutrinos.

[FE.02] Polarimeter for high energy photons

The physics program at TJNAF includes fundamental experiments with polarized photon beam in few GeV energy range. Development of the Polarimeter for use in Hall B experiments is the subject of present abstract. We have proposed to take advantage of the recent progress in silicon micro strip detectors for measurement of the geometry and angle correlation in electron positron pair production from an amorphous converter. A detailed analysis of the setup including MC simulation shows an experimental asymmetry \sigma_\parallel/\sigma_\perp \sim 1.7 in a wide range of the photon energies.

This asymmetry value is confirmed by our experimental results obtained using 100 percent polarized 40 MeV \gamma rays at Duke FEL.

[FE.03] Weak \Lambda Production in Electron Scattering from Protons

We calculate the differential cross section for the weak, strangeness changing, electron scattering process,e^- + p\longrightarrow \Lambda + \nu for incoming electron energies from 0.5 GeV to 6.0 GeV. We obtain as well the contributions of the individual form factors to the differential cross sections. We find that the differential cross sections peak as the maximal scattering angle for \Lambda is approached and that the peak height increases as the electron energy is increased. The behavior of the differential cross section near the maximal angle is discussed as is the possibility of observing this reaction at TJNAF. We also discuss this reaction as a tool for studying the weak strangeness changing current. .

[FE.04] Inclusive Neutrino Reactions in ^13C and Neutrino Backgrounds at KARMEN and Los Alamos

Inclusive neutrino reactions cross sections on ^13C for the reactions, \nu_e + ^13C\longrightarrow e^- + X and \nu_\mu + ^13C\longrightarrow \mu^- + X are calculated from threshold to several hundred MeV. Averaged cross sections over the Michel spectrum and over the Los Alamos muon neutrino spectrum are obtained. The method of calculation is a phenomenological tensor model. The consequences of these results with respect to the experiments at LAMPF and KARMEN are discussed.

[FE.05] Light-front quark model analysis for exclusive semileptonic B- and D-Decays

We present the analysis of exclusive semileptonic B- and D-decays using the constituents quark model based on the light-front quantization. Our method of analytic continuation to obtain the weak form factors avoids the difficulty associated with the contribution from the nonvalence quark-antiquark pair creation. Our numerical results are in a good agreement with the available experimental data.

[FE.06] The Reaction e^- + p\longrightarrow + \Sigma^0 + \nu_e and the Structure of the Weak Strangeness Changing Current

We calculate the differential cross section for the reaction, e^- + p\longrightarrow \Sigma^0 + \nu_e for incident electron energies from 1.0 to 6.0 GeV. We find the contributions of the various form factors to the differential cross section and show that only the vector and axial vector form factors make major contributions. We discuss this reaction as a possible test of the isospin structure of the weak strangeness changing current and discuss its relationship to weak \Lambda production. Finally we discuss the possibility of observing this reaction at TJNAF.

[FE.07] Virtual Antiparticle Pairs and Photon Propagation

Virtual pairs of elementary particles and their antiparticles, which are spontaneously created and annihilated in the quantum vacuum, are long-accepted consequences of quantum field theory. In this talk, it is shown that the polarizability of these virtual antiparticle pairs makes them a suitable medium for the propagation of electromagnetic radiation in vacuo. A semi-classical model of a photon propagating in this medium is constructed, and the electric polarizability and the density of virtual pairs are derived for each species of charged elementary particles (except quarks). The photon model, virtual pair polarizability, and resulting pair density together lead to a wave equation with the correct phase velocity for electromagnetic waves, c. This model is especially noteworthy because of the absence of adjustable parameters that might be required to correspond with observed photon properties.

[FE.08] Many Body Coulomb Gauge Hamiltonian Approach to the Hadrons

We report progress in approximately diagonalizing an effective QCD Hamiltonian by utilizing many body techniques. A confining potential determined by lattice gauge calculations and similar to the Cornell potential supplements our perturbative Hamiltonian.The effective Hamiltonian is then divided into the quark and the glue sectors The Bardeen-Cooper-Schrieffer (BCS) approximation is used for the ground state (vacuum) in both sectors to generate spontaneus chiral symmetry breaking and an improved quasi-particle basis, followed by the Tamm-Dancoff and Random Phase Approximations to reasonably reproduce the excited states (the particle spectrum). Here we focus on the quark sector and study the angular momentum splittings due to the relativistic Hamiltonian and the central role of chiral symmetry to generate the hyperfine splitting for the light flavor mesons. Finally, we discuss applications to many quark and gluon systems.

[FE.09] Compton Photon Polarimeter for the SLAC Linear Collider.

The longitudinal and transverse polarization of a high energy electron beam can be measured by the detection of photons produced in Compton scattering of the electrons from an intense polarized laser beam. We have built a calorimetric device based on the quartz fiber technology to perform polarization measurement at the SLAC Linear Collider. This detector was used to provide a cross check of the polarization measurement by the SLD Compton Polarimeter and allowed for improvement in the overall accuracy of many physics results produced by the SLD. Possible use of this technology in the polarimetry at future linear colliders is discussed.

[FE.10] Polarized Parity Violating Electron Scattering on ^3H and Its Relation to the ^3He Case

We calculate the asymmetry parameters,A, and figures of merit for polarized parity violating electron scattering from ^3H via the reaction,e^- + ^3H \longrightarrow ^3H + e^- for incident electron energies from 1.0 to 4.0 GeV. We find sharp variations in A due to cancellations similar to those reported for the reaction e^- + ^3He\longrightarrow e^- + ^3He but at different angles due to differences in the form factors for the two cases. We find that at small angles the asymmetry may be obtained to reasonably high accuracy for all energies considered here. We show that it might be possible to observe strange quark current contributions in this region. We also discuss the relationship between the ^3H and ^3He cases.

[FE.11] Using Micro Ion Beam Induced Current to Characterize and Improve Diamond Microstrip Detector

Diamond microstrip detectors are promising for use in intermediate and high energy experiments with large luminosity that requires high resolution tracking.

For this purppose, a thin 250 micron, (100) highhly oriented polycrystalline diamond film, has been developed by chemical vapor deposition (CVD) method. Characterization of this film is performed by measuring its transmitance in the spectrum region from IR to UV; by Raman measurement; and by electrical measurents. Thus far, the results have shown a high quality of diamond film.

A 6 MeV proton microbeam of few micrometers spot size is used to measure charge collection efficiency profile along the thickness of the detector. The measurements were carried out at several bias voltages and shaping times. Relative large collection distance were obtained, and assuming that the mobilities and trapping times are uniform, the electric field profile is obtained too.

[FE.12] Analytic Approximation for the Vacuum Polarization of Fermions in Static, Spherically Symmetric Spacetimes

A method for the computation of the vacuum polarization of fermions in static, spherically symmetric spacetimes is presented. It is found that one contribution to the vacuum polarization can be calculated analytically, and can serve as an analytical approximation for massless fermions. It is likely that a generalization of this method could be used to calculate the stress-energy tensor for fermions in static, spherically symmetric spacetimes.

Part F of program listing