Pion double charge exchange on the even selenium isotopes.
Pion-induced double charge exchange (,}) on {sup 76,78,80,82}Se, leading to the double isobaric analog states (DIAS) and the ground states of {sup 76,78,80,82}Kr, has been studied at a laboratory angle of 5{sup 0} and incident pion kinetic energy of 293.2 MeV. Cross sections for these transitions have been extracted, and those for the DIAS are compared to two simple models of pion double charge exchange.

title: Status of the focal plane polarimeter for Hall A at TJNAF
abstract: The focal plane polarimeter (FPP) for Hall A at the Thomas Jefferson National Accelerator Facility (TJNAF) is ready for experiments. The ability to calibrate the FPP on-site using elastic scattering of polarized electrons from an unpolarized hydrogen target is demonstrated. The ratio of the proton electric form factor to its magnetic form factor has been measured at Q2=0.810(GeV/c)2.

title: Measurement of the high energy two-body deuteron photodisintegration differential cross section.
abstract: The first measurements of the d(gamma,p)n differential cross section at forward angles and photon energies above 4 GeV were performed at the Thomas Jefferson National Accelerator Facility (JLab). The results indicate evidence of an angular dependent scaling threshold. Results at straight theta(cm) = 37 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 4 GeV, while those at 70 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 1.5 GeV.

title: UNIFIED ANALYSIS OF PION SINGLE AND DOUBLE CHARGE EXCHANGE SCATTERING IN THE RESONANCE REGION

title: A polarized gas internal target using a storage cell in an electron storage ring
abstract: The first experiment using a storage cell to increase the thickness of an internal polarized gas target in an electron beam storage ring was performed at the VEPP-3 facility. We describe the storage cell technique as applied in this measurement of elastic and inelastic electron scattering from tensor polarized deuterium. An analysis of electron-beam-induced depolarization of the target was performed and experimental tests were carried out which verify the effect. Other effects causing depolarization of the target are discussed as well as the means by which they are overcome. The effective p zz of the target, shown to be stable over 8 months, was 0.57±0.05; the total target thickness was increased over that of a jet target by a factor of fifteen.

title: Systematics of pion double-charge-exchange reactions on T = 0 nuclei
abstract: Pion induced double charge exchange on 12 C, 16 O, 24 Mg, 28 Si, 32 S, and 40 Ca exhibits forward-angle cross sections that vary rapidly with pion energy and fall off roughly as A −4 3 . Angular distributions at 164 MeV appear diffractive for targets of 12 C, 16 O, and 40 Ca.

title: Splitting of the P states in heavy quarkonium systems and the nature of the spin-dependent potential.
abstract: We consider the behavior of the splittings between the L = 1 states in heavy quarkonium systems. With standard assumptions, the ratio of mass splittings, R/sub chi/ = (M/sub 2/-M/sub 1/)/(M/sub 1/-M/sub 0/) is shown to grow slowly as we go from the lowest P states to their radial excitations, a behavior which is in accord with other theoretical calculations and is consistent with experiment. This behavior is the opposite of what is expected from a naive argument which we present. We show why the naive argument fails and how the phenomenological division of the potential into components which correspond to the exchange of a Lorentz scalar and vector can be made so as to obtain other behaviors.

title: Flavor-changing decays of the Z into heavy neutrinos.
abstract: We consider flavor-changing decays of the Z boson to a fourth-generation heavy neutrino and a light neutrino, which are induced at one loop in the standard model. Such decays have a characteristic monojet signature which makes them readily distinguished experimentally, unlike flavor-changing decays involving quarks. Like other such one-loop processes, however, they are very rare when reasonable mixing angles and intermediate fermion masses are considered.

title: Mixing of a heavy neutrino with the electron neutrino.
abstract: We show that recent monojet searches in electron-positron annihilation experiments can be used to extend significantly the limits on the mixing of a massive fourth-generation neutrino with the electron neutrino. When combined with other limits from hadron decays and secondary-vertex searches in hadron and electron-positron annihilation experiments, bounds of Vertical BarU/sub 14/Vertical Bar/sup 2/< or approx. =10/sup -6/ for neutrino masses of 10 MeV/c/sup 2/ to over 10 GeV/c/sup 2/ are obtainable by analysis of existing data.

title: Calculation of exclusive decay modes of the tau.
abstract: We update the calculation of the decays of the tau lepton into various modes using recent data on electron-positron annihilation into hadrons plus bounds that follow from isotopic-spin conservation. Comparison is made with exclusive branching-ratio data and inclusive charged-prong-distribution measurements in tau decays, and the difficulty in accounting for all the one-charged-prong decays as a sum of exclusive decay modes is discussed.

title: Phenomenology of an extra neutral gauge boson in electron-positron collisions.
abstract: Models with an extra neutral gauge boson (Z') are discussed. We review present limits on the properties of such a Z' which follow from requiring that the Z/sup 0/ mass not be shifted excessively through mixing, from neutral-current experiments, and from the structure of the mass matrix which follows from the Higgs-boson content of particular theories. We then examine what extensions in sensitivity can come from electron-positron annihilation experiments at the Z peak, with emphasis on the importance of cross-section measurements for final states involving lepton or quark pairs, followed by asymmetry measurements with polarized beams. Finally, we consider the additional information provided by asymmetry measurements in electron-positron collisions at energies above the Z.