7,505 research outputs found
Towards an Understanding of the New Charm and Charm-Strange Mesons
The observation of the D_{sJ}^*(2317), D_{sJ}(2460), and SELEX D^*_{sJ}(2632)
states with properties differing considerably from what was expected has led to
a renewed interest in hadron spectroscopy. In addition to these states,
non-strange partners of the D_{sJ} states have also been observed.
Understanding the D_0^* and D_1' states can provide important insights into the
D_{sJ} states. In this contribution I examine quark model predictions for the
D_0^* and D_1' states and discuss experimental measurements that can shed light
on them. I find that these states are well described as the broad, j=1/2
non-strange charmed P-wave mesons. In the latter part of this writeup I discuss
the c bar{s} possibilities for the SELEX D^*_{sJ}(2632) and measurements that
can shed light on it.Comment: Talk presented at the 1st Meeting of the APS Topical Group on
Hadronic Physics (Fermilab, Oct 24-26, 2004). 4 pages uses jpcon
Multigrid for hypersonic viscous two- and three-dimensional flows
The use of a multigrid method with central differencing to solve the Navier-Stokes equations for hypersonic flows is considered. The time dependent form of the equations is integrated with an explicit Runge-Kutta scheme accelerated by local time stepping and implicit residual smoothing. Variable coefficients are developed for the implicit process that removes the diffusion limit on the time step, producing significant improvement in convergence. A numerical dissipation formulation that provides good shock capturing capability for hypersonic flows is presented. This formulation is shown to be a crucial aspect of the multigrid method. Solutions are given for two-dimensional viscous flow over a NACA 0012 airfoil and three-dimensional flow over a blunt biconic
A Coulomb Gauge Model of Mesons
A model of mesons which is based on the QCD Hamiltonian in Coulomb gauge is
presented. The model relies on a novel quasiparticle basis to improve the
reliability of the Fock space expansion. It is also relativistic, yields chiral
pions, and is tightly constrained by QCD (quark masses are the only
parameters). Applications to hidden flavor mesons yield results which are
comparable to phenomenological constituent quark models while revealing the
limitations of such models.Comment: 13 pages, 1 eps figure, 5 table
Design Analysis of the Ares 1 Pogo Accumulator
Several accumulator designs and gas charge systems are considered in order to suppress POGO within the Ares I vehicle Upper Stage Liquid Ox ygen System. The thermodynamic and flow analysis completed to evaluat e candidate designs are presented and the results are used to evaluat e the ability of each concept to meet the levied suppression requirements. One annular accumulator design meets all suppression requirement s while also providing manufacturability and operability advantages. Of the two proposed charge systems to provide and maintain gas within the accumulator, a passive level control design meets the charge req uirements and maximizes reliability
Friction factors for smooth pipe flow
Friction factor data from two recent pipe flow experiments are combined to provide a comprehensive picture of the friction factor variation for Reynolds numbers from 10 to 36,000,000
Targeting unconventional host components for vaccination-induced protection against TB
The current tuberculosis (TB) vaccine, Bacille Calmette-Guerin (BCG), is effective in preventing TB in young children but was developed without a basic understanding of human immunology. Most modern TB vaccine candidates have targeted CD
Quantum Dissipation and Decoherence via Interaction with Low-Dimensional Chaos: a Feynman-Vernon Approach
We study the effects of dissipation and decoherence induced on a harmonic
oscillator by the coupling to a chaotic system with two degrees of freedom.
Using the Feynman-Vernon approach and treating the chaotic system
semiclassically we show that the effects of the low dimensional chaotic
environment are in many ways similar to those produced by thermal baths. The
classical correlation and response functions play important roles in both
classical and quantum formulations. Our results are qualitatively similar to
the high temperature regime of the Caldeira-Leggett model.Comment: 31 pages, 4 figure
Preliminary design characteristics of a subsonic business jet concept employing an aspect ratio 25 strut braced wing
The advantages of replacing the conventional wing on a transatlantic business jet with a larger, strut braced wing of aspect ratio 25 were evaluated. The lifting struts reduce both the induced drag and structural weight of the heavier, high aspect ratio wing. Compared to the conventional airplane, the strut braced wing design offers significantly higher lift to drag ratios achieved at higher lift coefficients and, consequently, a combination of lower speeds and higher altitudes. The strut braced wing airplane provides fuel savings with an attendant increase in construction costs
Magnetic moment non-conservation in magnetohydrodynamic turbulence models
The fundamental assumptions of the adiabatic theory do not apply in presence
of sharp field gradients as well as in presence of well developed
magnetohydrodynamic turbulence. For this reason in such conditions the magnetic
moment is no longer expected to be constant. This can influence particle
acceleration and have considerable implications in many astrophysical problems.
Starting with the resonant interaction between ions and a single parallel
propagating electromagnetic wave, we derive expressions for the magnetic moment
trapping width (defined as the half peak-to-peak difference in the
particle magnetic moment) and the bounce frequency . We perform
test-particle simulations to investigate magnetic moment behavior when
resonances overlapping occurs and during the interaction of a ring-beam
particle distribution with a broad-band slab spectrum.
We find that magnetic moment dynamics is strictly related to pitch angle
for a low level of magnetic fluctuation, , where is the constant and uniform background magnetic field.
Stochasticity arises for intermediate fluctuation values and its effect on
pitch angle is the isotropization of the distribution function .
This is a transient regime during which magnetic moment distribution
exhibits a characteristic one-sided long tail and starts to be influenced by
the onset of spatial parallel diffusion, i.e., the variance
grows linearly in time as in normal diffusion. With strong fluctuations
isotropizes completely, spatial diffusion sets in and
behavior is closely related to the sampling of the varying magnetic field
associated with that spatial diffusion.Comment: 13 pages, 10 figures, submitted to PR
Electron-capture branch of 100Tc and tests of nuclear wave functions for double-beta decays
We present a measurement of the electron-capture branch of Tc. Our
value, , implies that the
Mo neutrino absorption cross section to the ground state of Tc
is roughly one third larger than previously thought. Compared to previous
measurements, our value of prevents a smaller disagreement with
QRPA calculations relevant to double- decay matrix elements
- …