AION/Magis

Abstract:

We have simulated the evaporative cooling of a dilute gas of Bose particles including quantum statistics using a Monte Carlo method. This approach can model situations which are far away from quasiequilibrium such as occur during forced evaporative cooling. We have also simulated the dynamical formation of Bose-Einstein condensate for homogeneous and inhomogeneous Bose gases under the random-phase approximation. It was found that the rate of accumulation of Bose particles into low-energy states through collisions is increased by forced evaporation; and a macroscopic population at ground state can be reached at a time scale characterized by classical collision time for an inhomogeneous gas in a harmonic potential. We present the results of simulations for the evaporative cooling and formation of a Bose-Einstein condensate in one-, two-, and three-dimensional position cuts and energy cuts. © 1997 The American Physical Society.

Abstract:

An investigation focusing on the nonequilibrium evolution of a trapped Bose gas revealed that the formation of a Bose gas can be classified into three stages, namely: kinetic evolution; the formation of short range order; and the off-diagonal long-range order. Using a homogeneous gas consisting of sodium atoms. The evolution of non-Gaussian velocity distribution was observed. This indicates the accumulation of Bose particles at low energy states, but not necessarily the signature of the appearance of a macroscopic Bose-Einstein condensate. The condensate fraction will be very small when the ensemble of sodium atoms magnetically trapped in a harmonic potential is considered.

Abstract:

A search for the lepton-family-number-violating decays [Formula presented] and [Formula presented] has been performed using CLEO II data. No evidence of a signal has been found and the corresponding upper limits are [Formula presented] and [Formula presented] at 90% C.L. © 1997 The American Physical Society.