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.
125396434
TOP DECAYS WHEN m (t) approximates M (W) + m (b)
125631838
ALGEBRAIC PROPERTIES OF ELECTROMAGNETIC AND WEAK CURRENTS AND THEIR REPRESENTATION ON HADRON STATES
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:
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 ${N}^{**}(1520)$.
14177217
The physics of heavy flavors
Various aspects of the physics of heavy flavors and of CP violation are reviewed. 102 refs., 21 figs.
39737388
Measurement of tensor analyzing power in electron-deuteron elastic scattering.
An internal-target technique was used to make the first measurements of the tensor analyzing power {ital T}{sub 20} of electron-deuteron elastic scattering in the four-momentum-transfer range of 2--3 fm{sup {minus}1}. Polarized deuterium atoms were confined within a storage cell in the VEPP-3 electron storage ring in Novosibirsk to achieve a total target thickness of 3{times}10{sup 12} cm{sup {minus}2}, 15 times greater than was previously possible with an atomic-beam target alone. The results for {ital T}{sub 20} are in agreement with reasonable models of the deuteron wave function.
38995408
Pion double charge exchange on T=2 nuclei in the Delta 3/2,3/2 resonance region.
We present cross sections for the reactions {sup 44}Ca,{sup 56}Fe({pi}{sup +},{pi}{sup {minus}}) leading to the residual ground states and double-isobaric-analog states (DIAS) for incident pion energies from 100 to 300 MeV. Data include both angular distributions and 5{degree} excitation functions. Ground-state cross sections were also obtained from the {sup 12}C and {sup 16}O contaminants in the {sup 44}Ca target. The DIAS data are compared to known systematics and to theoretical predictions. Some features of the data are reproduced by the theoretical predictions, but major discrepancies exist.
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.
31258905
Analog of the T> giant dipole resonance in light nuclei.
Giant resonances were observed in (π+,π-) double charge exchange on 13C, 27Al, and 59Co at excitation energies of 8.8, 14.2, and 27.9 MeV, respectively, where the giant dipoles built on the isobaric analog states are expected to appear. Partial angular distributions were measured for both 13C and 27Al and observed to have a dipole shape. The resonance on the T=1/2 targets has a single isospin value (T=3/2) and is the analog of the T> giant dipole state in the above nuclei. The results are in good agreement with photonuclear reactions and indicate a new general method for an accurate determination of the T>=T+1 giant dipole state in T=1/2 nuclei.
6727190
Measurement of tensor polarization in elastic electron-deuteron scattering at large momentum transfer
Tensor polarization observables ( t(20), t(21), and t(22)) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 (GeV/c)(2). The experiment was performed at the Jefferson Laboratory in Hall C using the electron High Momentum Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q2 the deuteron charge form factors G(C) and G(Q). They are in good agreement with relativistic calculations and disagree with perturbative QCD predictions.