Baryonic Objects Research Articles

Dirac Phenomenology and Hyperon-Nucleus Interactions*)

We discuss various aspects of hyperon-nucleus interactions in the relativistic mean field theory. First, characteristics of Λ, Σ and Ξ hypernuclei, as well as multi-strange baryonic objects, are investigated. The spin-orbit splittings and magnetic moments are shown to be very sensitive to the value of the tensor coupling fωY. Second, optical potentials for Λ and Σ scattering off nuclei are developed based on a global nucleon-nucleus Dirac optical potential and SU(3) symmetry. The tensor coupling has a large effect on the predictions for the analyzing power. Third, the Dirac approach is used in the calculations of the non-mesonic decay of Λ hypernuclei. The large discrepancy between the decay rates and data suggests the need for additional meson exchanges.

Large-aperture BVRJK photometry of rich Abell clusters - Constraints on dark matter

This paper presents results of large (arcmin), single-aperture JK photometry and CCD BVR photometry on and near the centers of distant (Z between values of 0.14 and 0.20), rich Abell clusters. The colors of the integrated light of the cores of these clusters are consistent with those of nearby E and S0 galaxies. The absence of anomalous infrared emission provides the strongest constraint to date on the possible stellar make-up of the dark matter in clusters of galaxies, requiring K band (2.2 microns) mass-to-light ratios of the dark matter of (M/L)K not less than 400h. Indeed, no more than 5/h percent of the dark mass can be made of objects with mass greater than 0.1 solar mass. Although these results do not require a contribution of nonbaryonic matter, they provide some constraints on the mass function for baryonic objects which might compose the dark matter. These conclusions do not depend on the detailed distribution of the dark matter in the clusters. 35 refs.

Decrease of Velocity Differences between Baryonic Objects and Cold Dark Matter

It is investigated whether observed large-scale streaming of galaxies represents velocities of dark matter under explosion scenarios. It seeems that, although individual galaxies will not represent motions of dark matter, cluster of galaxies follows the velocity field of dark matter. The origin and upper limits of such field are considered.

Dragging Force on Galaxies Due to Streaming Dark Matter

It has been reported that galaxies in large regions (~102Mpc), including some clusters of galaxies, may be streaming coherently with velocities up to 600km/sec or more with respect to the rest frame determined by the microwave background radiation.) On the other hand, it is suggested that the dominant mass component of the universe is dark matter. Because we can only speculate the motion of dark matter from the galaxy motions, much attention should be paid to the correlation of velocities between the observed galaxies and cold dark matter. So we investigate whether such coherent large-scale streaming velocities are due to dark matter or only to baryonic objects which may be formed by piling up of gases due to some explosive events.