Showing papers in "Physical Review in 1999"

Experimental Test of Models of High-Plasma-Density, Radio-Frequency Sheaths

Abstract: Measurements of the rf-bias current and voltage applied to the substrate electrode of a high-density plasma reactor, combined with dc measurements of the ion current at the electrode and capacitive probe measurements of the plasma potential, enabled a rigorous, quantitative test of models of the electrical properties of the sheath adjacent to the electrode. The measurements were performed for argon discharges at 1.33 Pa (10 mTorr), ion current densities of 1.3--13 ${\mathrm{m}\mathrm{A}/\mathrm{c}\mathrm{m}}^{2}$, rf-bias frequencies of 0.1--10 MHz, and rf-bias voltages from less than 1 to more than 100 V. From the measurements, the current, voltage, impedance, and power of the sheath adjacent to the electrode were determined and were compared to model predictions. The properties of the opposing sheath, adjacent to grounded surfaces, were also determined. The behavior of the two sheaths ranged from nearly symmetric to very asymmetric. Changes in the symmetry are explained by models of the sheath impedance.

Interferometric measurements of the position of a macroscopic body: Towards observation of quantum limits

Abstract: Note: 213 Reference SAMLAB-ARTICLE-1999-025 Record created on 2009-05-12, modified on 2016-08-08

Charged track multiplicity in B meson decay

Abstract: We have used the CLEO II detector to study the multiplicity of charged particles in the decays of B mesons produced at the {upsilon}(4S) resonance. Using a sample of 1.5x10{sup 6} B meson pairs, we find the mean inclusive charged particle multiplicity to be 10.71{+-}0.02{sub -0.15}{sup +0.21} for the decay of the pair. This corresponds to a mean multiplicity of 5.36{+-}0.01{sub -0.08}{sup +0.11} for a single B meson. Using the same data sample, we have also extracted the mean multiplicities in semileptonic and nonleptonic decays. We measure a mean of 7.82{+-}0.05{sub -0.19}{sup +0.21} charged particles per BB(bar sign) decay when both mesons decay semileptonically. When neither B meson decays semileptonically, we measure a mean charged particle multiplicity of 11.62{+-}0.04{sub -0.18}{sup +0.24} per BB(bar sign) pair. (c) 2000 The American Physical Society.

Supersymmetric three cycles and supersymmetry breaking

Abstract: We describe physical phenomena associated with a class of transitions that occur in the study of supersymmetric three-cycles in Calabi-Yau (CY) threefolds. The transitions in question occur at real codimension one in the complex structure moduli space of the Calabi-Yau manifold. In type-IIB string theory, these transitions can be used to describe the evolution of a Bogomol'nyi-Prasad-Sommerfeld (BPS) state as one moves through a locus of marginal stability: at the transition point the BPS particle becomes degenerate with a supersymmetric two-particle state, and after the transition the lowest energy state carrying the same charges is a nonsupersymmetric two-particle state. In the IIA theory, wrapping the cycles in question with D6 branes leads to a simple realization of the Fayet model: for some values of the CY modulus gauge symmetry is spontaneously broken, while for other values supersymmetry is spontaneously broken. (c) 1999 The American Physical Society.

A Search for disoriented chiral condensate at the Fermilab Tevatron

Abstract: We present results from MiniMax (Fermilab T-864), a small test/experiment at the Fermilab Tevatron designed to search for the production of a disoriented chiral condensate (DCC) in p-p(bar sign) collisions at {radical}(s)=1.8 TeV in the forward direction, {approx}3.4<{eta}<{approx}4.2. Data, consisting of 1.3x10{sup 6} events, are analyzed using the robust observables developed in an earlier paper. The results are consistent with generic, binomial-distribution partition of pions into charged and neutral species. Limits on DCC production in various models are presented. (c) 2000 The American Physical Society.

psi(2S) ---> pi+ pi- J / psi decay distributions

Abstract: Using a sample of 3.8 M psi(2S) events accumulated with the BES detector, the process psi(2S) -> pi^+ pi^- J/psi is studied. The angular distributions are compared with the general decay amplitude analysis of Cahn. We find that the dipion system requires some D-wave, as well as S-wave. On the other hand, the J/psi-(pi pi) relative angular momentum is consistent with being pure S-wave. The decay distributions have been fit to heavy quarkonium models, including the Novikov-Shifman model. This model, which is written in terms of the parameter kappa, predicts that D-wave should be present. We determine kappa = 0.183 +/- 0.002 +/- 0.003 based on the joint dipion mass - cos theta distribution. The fraction of D-wave as a function of the dipion mass is found to decrease with increasing dipion mass, in agreement with the model. We have also fit the Mannel-Yan model, another model that allows D-wave.