How the First Stars Regulated Star Formation. II. Enrichment by Nearby Supernovae

Metals from Population III (Pop III) supernovae led to the formation of less massive Pop II stars in the early universe, altering the course of evolution of primeval galaxies and cosmological reionization. There are a variety of scenarios in which heavy elements from the first supernovae were taken up into second-generation stars, but cosmological simulations only model them on the largest scales. We present small-scale, high-resolution simulations of the chemical enrichment of a primordial halo by a nearby supernova after partial evaporation by the progenitor star. We find that ejecta from the explosion crash into and mix violently with ablative flows driven off the halo by the star, creating dense, enriched clumps capable of collapsing into Pop II stars. Metals may mix less efficiently with the partially exposed core of the halo, so it might form either Pop III or Pop II stars. Both Pop II and III stars may thus form after the collision if the ejecta do not strip all the gas from the halo. The partial evaporation of the halo prior to the explosion is crucial to its later enrichment by the supernova.Comment: Accepted to Ap

New measurement of charge asymmetry xF3x{F}_3 from HERA

After presenting the recent measurements of neutral current cross section in DIS at HERA, we explain the effect of the $\gamma-Z_0$ interference at the electro-weak scale, visible on these data. Then, the beam charge difference $x{F}_3$ is measured and the interference itself is extracted. Results are discussed in the context of perturbative QCD.Comment: 4 pages, 3 figures, proceedings of the International Workshop on Positrons at Jefferson Lab (March 25-27, 2009), Thomas Jefferson National Accelerator Facility, Newport News, V

Have we seen anything beyond (N)NLO DGLAP at HERA?

The evidence from HERA for parton saturation, and other low-$x$ effects beyond the conventional DGLAP formalism, is recalled and critically reviewed in the light of new data and analyses presented at the conference.Comment: 4 pages, 5 figures, Contribution to the discussion session at Intenrational Symposium on Multiparticle Dynamics, ISMD08, Hambur

ZEUS Results

Several results from the ZEUS Collaboration were presented at this Workshop. The highlights are presented in this summary, and include results from NLO QCD fits and determination of alphas, from forward jets and diffractive final states, from pentaquarks and searches and from heavy flavour production. Also the first results from the analysis of the HERA II e+p/e-p data are shown.Comment: 12 pages, Proceedings of the DIS05 Workshop, Madison, 200