How to Reach a Thousand-Second in-Plane Polarization Lifetime with 0.97-GeV/c Deuterons in a Storage Ring

We observe a deuteron beam polarization lifetime near 1000 s in the horizontal plane of a magnetic storage ring (COSY). This long spin coherence time is maintained through a combination of beam bunching, electron cooling, sextupole field corrections, and the suppression of collective effects through beam current limits. This record lifetime is required for a storage ring search for an intrinsic electric dipole moment on the deuteron at a statistical sensitivity level approaching 10^{-29}  e cm.

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. The spin tune is deduced from the up-down asymmetry of deuteron-carbon scattering. In a time interval of 2.6 s, the spin tune was determined with a precision of the order 10^{-8}, and to 1×10^{-10} for a continuous 100 s accelerator cycle. This renders the presented method a new precision tool for accelerator physics; controlling the spin motion of particles to high precision is mandatory, in particular, for the measurement of electric dipole moments of charged particles in a storage ring.

Self-consistent calculations of the electric giant dipole resonances in light and heavy nuclei

While bulk properties of stable nuclei are successfully reproduced by mean-field theories employing effective interactions, the dependence of the centroid energy of the electric giant dipole resonance on the nucleon number A is not. This problem is cured by considering many-particle correlations beyond mean-field theory, which we do within the quasiparticle time blocking approximation. The electric giant dipole resonances in 16O, 40Ca, and 208Pb are calculated using two new Skyrme interactions.

Evidence for an excited hyperon state in pp --> pK+Y0*

Indications for the production of a neutral excited hyperon in the reaction pp --> pK+Y0* are observed in an experiment performed with the ANKE spectrometer at COSY-Jülich at p(beam) = 3.65 GeV/c. Two final states were investigated simultaneously, viz. Y0* --> pi+X- and pi-X+, and consistent results were obtained in spite of the quite different experimental conditions. The parameters of the hyperon state are M(Y0*) = (1480 +/-15) MeV/c2 and gamma(Y0*) = (60 +/- 15) MeV/c2. The production cross section for Y0* decaying through these channels is of the order of few hundred nanobarns. Since the isospin of the Y0* has not been determined here, it could either be an observation of the sigma(1480), a one-star resonance of the Particle Data Group tables, or, alternatively, a lambda hyperon. Relativistic quark models for the baryon spectrum do not predict any excited hyperon in this mass range and so the Y0* may be of exotic nature.