New Method for a Continuous Determination of the Spin Tune in Storage Rings and Implications for Precision Experiments.

A new method to determine the spin tune is described and tested. In an ideal planar magnetic ring, the spin tune-defined as the number of spin precessions per turn-is given by ν(s)=γG (γ is the Lorentz factor, G the gyromagnetic anomaly). At 970  MeV/c, the deuteron spins coherently precess at a frequency of ≈120  kHz in the Cooler Synchrotron COSY.

Abashian-Booth-Crowe effect in basic double-pionic fusion: a new resonance?

We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction pn→dπ(0)π(0) over the full energy region of the ABC effect, a pronounced low-mass enhancement in the ππ-invariant mass spectrum. The measurements, which cover also the transition region to the conventional t-channel ΔΔ process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section.

Casimir interaction among objects immersed in a fermionic environment.

Using ensembles of two, three, and four spheres immersed in a fermionic background we evaluate the (integrated) density of states and the Casimir energy. We thus infer that for sufficiently smooth objects, whose various geometric characteristic lengths are larger then the Fermi wave length one can use the simplest semiclassical approximation (the contribution due shortest periodic orbits only) to evaluate the Casimir energy. We also show that the Casimir energy for several objects can be represented fairly accurately as a sum of pairwise Casimir interactions between pairs of objects.