31144850
Neutron and proton matrix elements for 21+ transitions in T=1 nuclei from pion inelastic scattering.
Cross sections have been measured for ..pi../sup +/ and ..pi../sup -/ inelastic scattering to the 2/sub 1//sup +/ levels of /sup 18/O, /sup 22/Ne, /sup 26/Mg, /sup 30/Si, and /sup 34/S. The data are used to infer neutron and proton quadrupole-matrix elements for these transitions. The matrix elements extracted from the pion data are in good agreement with their corresponding electromagnetic matrix elements. These results indicate that the use of the distorted-wave impulse-approximation is a valid procedure for this class of transition.
121458775
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.
55880852
Status of the focal plane polarimeter for Hall A at TJNAF
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.
120867307
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.
123035410
UNIFIED ANALYSIS OF PION SINGLE AND DOUBLE CHARGE EXCHANGE SCATTERING IN THE RESONANCE REGION
34302340
Measurement of the high energy two-body deuteron photodisintegration differential cross section.
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.
14921407
Splitting of the P states in heavy quarkonium systems and the nature of the spin-dependent potential.
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.
17844622
Extra neutral gauge bosons in electron-positron collisions at resonance.
A simple extension of the standard model to an sum x U(l)y x U(1) gauge symmetry is considered. The symmetry is broken by vacuum expectation values of one doublet and one singlet scalar field, resulting in a second massive neutral gauge boson. Electron positron collisions at this 2’ resonance are calculated. Aside from the possibility of 2’ decays into exotic fermions which fill out the irreducible representations of grand unified theories, there generally are important decay modes into W+Wand Z”Ho coming from mixing between the 2’ and the 2 of the standard model, even after imposing the constraints from experiment on the magnitude of the mixing angle. Submitted to Physical Review D * Work supported by the Department of Energy, contract DE AC03 76SF00515.
18057410
Flavor-changing decays of the Z into heavy neutrinos.
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.