Relativistic and Binding Energy Corrections to Direct Photon Production In Upsilon Decay

A systematic gauge-invariant method is used to calculate the rate for an upsilon meson to decay inclusively into a prompt photon. An expansion is made in the quark relative velocity v, which is a small natural parameter for heavy quark systems. Inclusion of these O(v^2) corrections tends to increase the photon rate in the middle z range and to lower it for larger z, a feature supported by the data.Comment: 13 pages, LateX, One figure (to be published in Phys. Rev. D, Sept. 1, 1996

DETC2005-84855 VIBRATION LOCALIZATION IN NEAR-PERIODIC COUPLED TWO-DIMENSIONAL RESONATOR ARRAYS

ABSTRACT The effects of small deviations from periodicity on the vibration behavior of coupled arrays of mechanical resonators are investigated, and the consequences for energy propagation across such arrays are described. Existing localization theory is applied to demonstrate that one-dimensional arrays designed as bandpass filters are particularly sensitive to aperiodicity when narrow passband requirements dictate weak interresonator coupling. A novel two-dimensional array of resonators is proposed that is less sensitive to disorder than one-dimensional arrays, improving filter performance without the need for improved manufacturing tolerances. Numerical simulations of a simple model are employed to demonstrate the effects of disorder on one-and two-dimensional arrays, and a case study design is discussed that includes statistical investigation using finite-element analysis and experimental measurements of a prototype two-dimensional array

Acoustic cavities in 2D heterostructures

Two-dimensional (2D) materials offer unique opportunities in engineering the ultrafast spatiotemporal response of composite nanomechanical structures. In this work, we report on high frequency, high quality factor (Q) 2D acoustic cavities operating in the 50–600 GHz frequency (f) range with f × Q up to 1 × 10(14). Monolayer steps and material interfaces expand cavity functionality, as demonstrated by building adjacent cavities that are isolated or strongly-coupled, as well as a frequency comb generator in MoS(2)/h-BN systems. Energy dissipation measurements in 2D cavities are compared with attenuation derived from phonon-phonon scattering rates calculated using a fully microscopic ab initio approach. Phonon lifetime calculations extended to low frequencies (<1 THz) and combined with sound propagation analysis in ultrathin plates provide a framework for designing acoustic cavities that approach their fundamental performance limit. These results provide a pathway for developing platforms employing phonon-based signal processing and for exploring the quantum nature of phonons