[en] Results of a search for coherent charm production in 800 GeV/c proton-Si interactions will be presented. The data for this analysis were recorded in the Fermilab E653 spectrometer. An active silicon wafer target and a multiplicity jump trigger were used

[en] The hopping rate of localized defects interacting with a two-dimensional electron system is studied. It is shown that, at low temperatures, the hopping rate is an oscillatory function of the inverse of the magnetic field. The period and the amplification of the oscillations are independent of the electron-defect interaction and the detailed structure of the sample. It is predicted that the temperature dependence of the hopping rate differs significantly between the cases of filled and half-filled Landau levels. (Author) (13 refs., 2 figs.)

[en] This thesis reports the results from two independent analysis: In the first analysis, the branching ratio for the decay mode D⁺ → K^*0μ⁺ν has been measured with two methods. The first uses D⁰ → K^-μ⁺ν for normalization, and yields the result B(D⁺ → K^*0μ⁺ν) = (3.25 ± 0.71 ± 0.75)%. From this method we also obtain the direct measurement Γ(D⁺ → K^*0μ⁺ν)/Γ(D⁰ → K^-μ⁺ν) = 0.43 ± 0.09 ± 0.09. The second method uses the mode D⁺ → K^-π⁺π⁺ for normalization and yields B(D⁺ → K^*0μ⁺ν) = (3.57 ± 0.96)%. In the second analysis, coherent charm production in 800 GeV/c proton-Silicon interactions was searched for in the decay modes D⁺ → K^-π⁼π⁺, D⁰ → K^-π⁺, D⁰ → K^-π⁺π⁺π^- and Λ⁺_c → pK^-π⁺. The data were recorded in the Fermilab E653 spectrometer. An active silicon wafer target assembly and a multiplicity jump trigger were used. No coherent charm signals were observed, and 90% confidence level upper limit for coherent charm pair production was determined to be 26 μb per silicon nucleus. The results are interpreted as an upper limit of 0.2% on the amount of intrinsic charm in the proton

[en] By using exact wave functions of an electron in a terahertz laser field, we calculated the electron resonant tunneling through a double barrier structure. It is found that the laser field has two effects on the current voltage characteristics. First, it introduces additional tunneling states through the structure due to multiple photon processes (emission, absorption, scattering). Second, it reduces the width of the bistable region. At high field strength and low frequencies, the bistability can be completely removed. This can provide a method by which to tune the bistable region in a double barrier structure. [copyright] 2001 American Institute of Physics

[en] We are studying the yrast structure of very neutron-rich nuclei around doubly magic ¹³²Sn by analyzing fission product γ-ray data from a ²⁴⁸Cm source at Eurogam II. Yrast cascades in several few-valence-particle nuclei have been identified through γγ cross coincidences with their complementary fission partners. Results for two-valence-particle nuclei ¹³²Sb, ¹³⁴Te, ¹³⁴Sb and ¹³⁴Sn provide empirical nucleon-nucleon interactions which, combined with single-particle energies already known in the one-particle nuclei, are essential for shell-model analysis in this region. Findings for the N = 82 nuclei ¹³⁴Te and ¹³⁵I have now been extended to the four-proton nucleus ¹³⁶Xe. Results for the two-neutron nucleus ¹³⁴Sn and the N = 83 isotones ¹³⁴Sb, ¹³⁵Te and ¹³⁵I open up the spectroscopy of nuclei in the northeast quadrant above ¹³²Sn

[en] It is shown that in insulators, muonium should delocalize into Bloch waves up to quite high temperatures, of order 70 K. The dissipative coupling to Debye phonons will give a long-time stochastic behavior, and a microscopic theory quantitatively explains the puzzling T^-3 behavior observed for the quantum diffusion coefficient at intermediate temperatures, in recent experiments in KCl. The theory is generally applicable to particle motion in the presence of a phonon heat bath. (Author) (8 refs., fig.)

[en] The correlation coefficients a , A , and B in neutron β decay are proportional to the ratio of the axial-vector-to-vector weak coupling constants, g_A/g_V , to leading recoil order. With the advent of the next generation of neutron-decay experiments, the recoil-order corrections to these expressions become experimentally accessible, admitting a plurality of standard model (SM) tests. The measurement of both a and A , e.g., allows one to test the conserved-vector-current (CVC) hypothesis and to search for second-class currents (SCC) independently. The anticipated precision of these measurements suggests that the bounds on CVC violation and SCC from studies of nuclear β decay can be qualitatively bettered

[en] Short communication

[en] An analysis of the neutral beam (NB) current drive for the International Thermonuclear Experimental Reactor (ITER) is performed. The NB deposition profile for a model elliptic equilibrium is evaluated for arbitrary density profiles. Multistep ionization is accounted for. The NB current density is calculated by using an approximate solution of the Fokker-Planck equation. A parameter scan is performed by changing electron density, plasma temperature, the plasma effective ionic charge Z_eff, beam energy E_b, beam mass number, beam section, and tangency radius of the beam center. The largest values of the current drive figure of merit γ_NB = I_NBnR/P are obtained for the largest beam energy. The obtained value of γ_NB for the ITER reference scenario is γ_NB = 0.6 for E_b = 1.3 MeV and Z_eff = 2. 20 refs., 20 figs., 1 tab

[en] In this paper, the effect of stochastic magnetic field (SMF) on the eigenmodes of low frequency drift wave is analysed. We show that the existence of SMF can affect the response of electrons to the wave, so that the electron dispersion function varies. In the vicinity of the rational magnetic surface (where k/sub parallel/ approx. =0), the variation is particularly significant. The SMF can make the electron dispersion function considerably smoother, and the change in electron dispersion function may greatly affect the stability of the eigenmodes of drift wave. It is shown that if the SMF is strong enough (but still within the region achievable experimentally), the so-called universal modes of drift wave may become absolutely unstable