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.
120213968
Symmetry Predictions from Sum Rules without Saturation
The application of sum rules derived from current commutation relations to give $\mathrm{SU}(6)$-like results is developed without the assumption of saturation. We first derive a consistency condition by comparing sum rules, and then study the sum rules for $\frac{1}{g_{A}^{}{}_{}{}^{2}}$ and the isovector charge radii, replacing the assumption of saturation with a simple dynamical model for the remaining continuuum contribution. This results in several $\mathrm{SU}(6)$-like predictions which contain important correction factors to the results previously derived assuming saturation. We have also re-examined the experimental data for the sum rule for $\frac{{〈r_{N}^{}{}_{}{}^{2}〉}^{V}}{6}$, and find that it converges below 1 GeV like the sum rule for $\frac{1}{g_{A}^{}{}_{}{}^{2}}$ when account is taken of the contribution to the sum rule of the large resonant ${M}_{1+}$ and nonresonant ${\mathrm{E}}_{0+}$ multipoles in pion photoproduction, and of the ${N}^{**}(1520)$.
125631838
ALGEBRAIC PROPERTIES OF ELECTROMAGNETIC AND WEAK CURRENTS AND THEIR REPRESENTATION ON HADRON STATES
125396434
TOP DECAYS WHEN m (t) approximates M (W) + m (b)
14177217
The physics of heavy flavors
Various aspects of the physics of heavy flavors and of CP violation are reviewed. 102 refs., 21 figs.
119841878
CP violation in K decays
As in the case for much of contemporary research in high energy physics, the area of CP (the product of charge conjugation and parity) violation in K decays is to be seen in the context of a much broader effort of looking for physics beyond the Standard Model. One of the specific types of such physics is represented by the possibility of a fourth family, as exemplified by the title and main focus of this conference. From the broader perspective of looking for new physics of any kind, there are two principal avenues:
42500569
Pion double charge exchange on the even selenium isotopes.
Pion-induced double charge exchange ({pi}{sup +},{pi}{sup {minus}}) 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.
40204933
M4 transitions observed in pion inelastic scattering on 15N.
Cross sections for ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$ elastic and inelastic scattering to states in $^{15}\mathrm{N}$ have been measured at an incident pion energy of 164 MeV. Transitions to states at 10.7, 12.5, 14.0, and 17.2 MeV were found to contain significant M4 strength. The M4 assignments are supported both by angular distribution shapes and by additional ${\ensuremath{\pi}}^{+}$ cross sections measured at 120 and 260 MeV. The angular distributions are compared with distorted-wave impulse-approximation calculations to extract isoscalar and isovector spectroscopic amplitudes. These amplitudes are compared with model predictions.
26489055
First measurements of jet production rates in deep-inelastic lepton-proton scattering.
The first measurements of forward multijet rates in deep-inelastic lepton scattering are presented. Data were taken with a 490-GeV muon beam incident on a hydrogen target. The jets were defined using the GADE algorithm. The measured rates are presented as a function of the jet resolution parameter {ital y}{sub cut}, and as a function of the virtual-photon--proton center-of-momentum energy {ital W}, in the range 13{le}{ital W}{le}33 GeV. Comparisons are made to the predictions of the Lund Monte Carlo programs and good agreement is obtained when QCD corrections are included in the model.
34447194
Forward-angle charged-pion electroproduction in the deuteron.
A direct experimental determination has been made of the ratio of the forward-angle positive-pion electroproduction cross section for a proton bound in the deuteron with that of a free proton for invariant masses of 1160 and 1232 MeV. A significant quenching of the reaction in the deuteron is observed.
26580602
Nuclear-structure aspects of nonanalog pion double charge exchange.
The sensitivity of pion double charge exchange to nuclear structure in the shell model is examined. We consider the nonanalog ground-state to ground-state (T = 0 to T = 2) transitions on a variety of nuclear targets. The reaction model, which assumes that double charge exchange is driven by a ..pi..+rho-meson--mediated, ..delta../sub 33/-nucleon interaction, reproduces the energy dependence and shape of the empirical cross section for all the (..pi../sup +/,..pi../sup -/) transitions examined. The magnitude of the cross section is particularly sensitive to collectivity in the nuclear wave functions. All parameters of the model, with the exception of the range of the meson-..delta../sub 33/ form factor, are fixed by theoretical arguments. The form factor is then determined by normalizing to the /sup 16/O(..pi../sup +/,..pi../sup -/) /sup 16/ Ne cross section. Predictions are made for a variety of other low-lying 0/sup +/ transitions.