Research on thermophoretic and inertial aspects of ash particle deposition on heat exchanger surfaces in coal-fired equipment

During this third quarter of Grant DE-FG22-86 PC 90756, we have obtained preliminary experimental results on the deposition behavior of submicron and supermicron solid particles (MgO, Al[sub 2]O[sub 3]) on a two-dimensional surface exposed to a high temperature/velocity particle laden'' atmospheric pressure jet. The uniform velocity ( plug flow'') jet, with temperatures up to about 1520 K, derives from a pressurized gaseous fuel microcombustion chamber (110 cc) equipped with a platinum guiding (exit) channel. Particles were generated by several methods (Berglund-Liu type aerosol generator, ultrasonic nebulizer, or syringe feeder with aerodynamic particle off-take) and were introduced into the combustion chamber with a carrier stream of nitrogen or air. Laser light scattering and reflectivity techniques were used for the study of particle deposition, supplemented by post-mortem microscopy on the exposed surface. We observed a linear deposition rate of submicron particles due to the thermophoretic mechanism (until the first layer was developed) under both high and low velocity conditions. On the contrary, supermicron particle deposits reach a steady-state, evidently due to a dynamic equilibrium between particle deposition and dislodging caused by the impacting particles. At several temperatures particle-free subsonic gas jets (up to 120 m/sec) were unable to remove the submicron particle layer

B→DsπB \to D_s \pi and the tree amplitude in B→π+π−B \to \pi^+ \pi^-

The recently-observed decay $B^0 \to D_s^+ \pi^-$ is expected to proceed mainly by means of a tree amplitude in the factorization limit: $B^0 \to \pi^- {(W^+)}^*$, ${(W^+)}^* \to D_s^+$. Under this assumption, we predict the corresponding contribution of the tree amplitude to $B^0 \to \pi^+ \pi^-$. We indicate the needed improvements in data that will allow a useful estimate of this amplitude with errors comparable to those accompanying other methods. Since the factorization hypothesis for this process goes beyond that proved in most approaches, we also discuss independent tests of this hypothesis.Comment: 7 pages, LaTeX, 1 figure, to be submitted to Phys. Rev. D (Brief Reports

Final-State Phases in Doubly-Cabibbo-Suppressed Charmed Meson Nonleptonic Decays

Cabibbo-favored nonleptonic charmed particle decays exhibit large final-state phase differences in $\bar K \pi$ and $\bar K^* \pi$ but not $\bar K \rho$ channels. It is of interest to know the corresponding pattern of final-state phases in doubly-Cabibbo-suppressed decays, governed by the $c \to d u \bar s$ subprocess. An experimental program is outlined for determining such phases via measurements of rates for $D \to K^* \pi$ and $K (\rho, \omega,\phi)$ channels, and determination of interference between bands in Dalitz plots. Such a program is feasible at planned high-intensity sources of charmed particles.Comment: 12 pages, LaTeX, 2 figures, to be submitted to Phys. Rev. D. Revised versio

Strong and Weak Phases from Time-Dependent Measurements of B→ππB \to \pi \pi

Time-dependence in $B^0(t) \to \pi^+ \pi^-$ and \ob(t) \to \pi^+ \pi^- is utilized to obtain a maximal set of information on strong and weak phases. One can thereby check theoretical predictions of a small strong phase $\delta$ between penguin and tree amplitudes. A discrete ambiguity between $\delta \simeq 0$ and $\delta \simeq \pi$ may be resolved by comparing the observed charge-averaged branching ratio predicted for the tree amplitude alone, using measurements of $B \to \pi l \nu$ and factorization, or by direct comparison of parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix with those determined by other means. It is found that with 150 fb$^{-1}$ from BaBar and Belle, this ambiguity will be resolvable if no direct CP violation is found. In the presence of direct CP violation, the discrete ambiguity between $\delta$ and $\pi - \delta$ becomes less important, vanishing altogether as $|\delta| \to \pi/2$. The role of measurements involving the lifetime difference between neutral $B$ eigenstates is mentioned briefly.Comment: 14 pages, LaTeX, 5 figures, to be published in Phys. Rev. D. Updated version with one reference change

Reevaluation of the role of nuclear uncertainties in experiments on atomic parity violation with isotopic chains

In light of new data on neutron distributions from experiments with antiprotonic atoms [ Trzcinska {\it et al.}, Phys. Rev. Lett. 87, 082501 (2001)], we reexamine the role of nuclear-structure uncertainties in the interpretation of measurements of parity violation in atoms using chains of isotopes of the same element. With these new nuclear data, we find an improvement in the sensitivity of isotopic chain measurements to ``new physics'' beyond the standard model. We compare possible constraints on ``new physics'' with the most accurate to date single-isotope probe of parity violation in the Cs atom. We conclude that presently isotopic chain experiments employing atoms with nuclear charges Z < 50 may result in more accurate tests of the weak interaction.Comment: 6 pages, 1 fig., submitted to Phys. Rev.

CPT, T, and Lorentz Violation in Neutral-Meson Oscillations

Tests of CPT and Lorentz symmetry using neutral-meson oscillations are studied within a formalism that allows for indirect CPT and T violation of arbitrary size and is independent of phase conventions. The analysis is particularly appropriate for studies of CPT and T violation in oscillations of the heavy neutral mesons D, B_d, and B_s. The general Lorentz- and CPT-breaking standard-model extension is used to derive an expression for the parameter for CPT violation. It varies in a prescribed way with the magnitude and orientation of the meson momentum and consequently also with sidereal time. Decay probabilities are presented for both uncorrelated and correlated mesons, and some implications for experiments are discussed.Comment: 11 pages, references added, accepted in Physical Review

Phase diagram of the one-dimensional extended attractive Hubbard model for large nearest-neighbor repulsion

We consider the extended Hubbard model with attractive on-site interaction U and nearest-neighbor repulsions V. We construct an effective Hamiltonian H_{eff} for hopping t<<V and arbitrary U<0. Retaining the most important terms, H_{eff} can be mapped onto two XXZ models, solved by the Bethe ansatz. The quantum phase diagram shows two Luttinger liquid phases and a region of phase separation between them. For density n<0.422 and U<-4, singlet superconducting correlations dominate at large distances. For some parameters, the results are in qualitative agreement with experiments in BaKBiO.Comment: 6 pages, 3 figures, submitted to Phys. Rev.

A Quantitative Model of Energy Release and Heating by Time-dependent, Localized Reconnection in a Flare with a Thermal Loop-top X-ray Source

We present a quantitative model of the magnetic energy stored and then released through magnetic reconnection for a flare on 26 Feb 2004. This flare, well observed by RHESSI and TRACE, shows evidence of non-thermal electrons only for a brief, early phase. Throughout the main period of energy release there is a super-hot (T>30 MK) plasma emitting thermal bremsstrahlung atop the flare loops. Our model describes the heating and compression of such a source by localized, transient magnetic reconnection. It is a three-dimensional generalization of the Petschek model whereby Alfven-speed retraction following reconnection drives supersonic inflows parallel to the field lines, which form shocks heating, compressing, and confining a loop-top plasma plug. The confining inflows provide longer life than a freely-expanding or conductively-cooling plasma of similar size and temperature. Superposition of successive transient episodes of localized reconnection across a current sheet produces an apparently persistent, localized source of high-temperature emission. The temperature of the source decreases smoothly on a time scale consistent with observations, far longer than the cooling time of a single plug. Built from a disordered collection of small plugs, the source need not have the coherent jet-like structure predicted by steady-state reconnection models. This new model predicts temperatures and emission measure consistent with the observations of 26 Feb 2004. Furthermore, the total energy released by the flare is found to be roughly consistent with that predicted by the model. Only a small fraction of the energy released appears in the super-hot source at any one time, but roughly a quarter of the flare energy is thermalized by the reconnection shocks over the course of the flare. All energy is presumed to ultimately appear in the lower-temperature T<20 MK, post-flare loops

Precise calculation of parity nonconservation in cesium and test of the standard model

We have calculated the 6s-7s parity nonconserving (PNC) E1 transition amplitude, E_{PNC}, in cesium. We have used an improved all-order technique in the calculation of the correlations and have included all significant contributions to E_{PNC}. Our final value E_{PNC} = 0.904 (1 +/- 0.5 %) \times 10^{-11}iea_{B}(-Q_{W}/N) has half the uncertainty claimed in old calculations used for the interpretation of Cs PNC experiments. The resulting nuclear weak charge Q_{W} for Cs deviates by about 2 standard deviations from the value predicted by the standard model.Comment: 24 pages, 8 figure

Weak Phase γ\gamma from Bs(t)→K+K−B_s(t) \to K^+ K^-

We re-examine the time-dependent rates of \bs(t) \to K^+ K^- and \obs(t) \to K^+ K^-, including a lifetime difference between neutral \bs mass eigenstates. The two rates, normalized by the rate of \bs \to \ko \ok, are used to obtain ambiguity-free information on a strong phase and on the weak phase $\gamma$. We discuss the sensitivity of extracting $\gamma$ to the measured quantities, and find that an error of $\pm 10^\circ$ in $\gamma$ is possible for a sample of several thousand \bs(t) \to K^+ K^- decays. This study is complementary to a recent similar analysis of the U-spin related decays \bo(t) \to \pi^+\pi^- and \ob(t) \to \pi^+\pi^-.Comment: 12 pages, LaTeX, 3 figures, revised version submitted to Phys. Rev.