Rapidity dependence of large-p_t hadron production at RHIC

We study the dependence of parton energy loss (quenching) on rapidity in ultra-relativistic nuclear collisions at RHIC. This can provides invaluable information on the density of the medium, which should be more dilute going away from mid-rapidity, thereby reducing the effect of quenching. We predict a clear effect at moderate transverse momenta $\sim$ 3 GeV.Comment: 4 pages, latex, 3 eps figure

Excitation of Color Degrees of Freedom of Nuclear Matter and J/ψJ/\psi Suppression

In high energy nuclear collisions, the conventional Glauber model is commonly used to evaluate the contribution to $J/\psi$ suppression originating from the inelastic interaction with colorless bound nucleons. This requires an effective value for the $J/\psi$-nucleon absorption cross section which is larger than theoretically expected. On the other hand, multiple nucleon-nucleon collisions mediated by color exchange interactions, excite their color degrees of freedom. We investigate the importance of this effect and find that these excited states provide a larger cross section for $J/\psi$ absorption. We conclude that the related corrections are important to explain the effective value extrapolated from experiment.Comment: 21 pages Latex, 8 postscript figure

Radioactive Governance: The Politics of Expertise after Fukushima

This dissertation focuses on Japanese public and state responses to the release of radioactive contamination after the 2011 Fukushima nuclear disaster. I argue that the Fukushima nuclear disaster has led to the emergence of new forms of expertise in governing radioactive risks. These include techniques of governance that attempt to normalize peoples relationships with nuclear matter as an everyday concern. They also include decentralized strategies that empower victims of the disaster by providing access to technoscientifc practices of radiation monitoring and delegating radiation protection from the state to the citizens. My findings uncover a major shift in how societies have formerly organized responses to radioactive risks. In the aftermath of nuclear accidents, scholars have criticized central authoritarian decisions, in which state management of radioactive hazards was associated with politics of secrecy, victimhood, or public knowledge deficit. At stake in Fukushima is an increased normalization of citizens relationship with residual radioactivity, which is transformed into an everyday concern, rather than being represented as something exceptional. This is not only done by state experts, but equally via the increased activity of citizen scientists that collectively monitor residual radioactivity. My research is a significant departure from traditional sociocultural works that predominantly focus on micro-scale studies, such as how prior sociocultural factors influence a group understanding of radioactive risks. By highlighting major shifts in the structure of expertise and the regulation of life amidst toxic exposure, my research highlights how the management of contamination risks is evolving in an era where the impacts of modernization represent permanent marks on the planet

Effects of collective expansion on light cluster spectra in relativistic heavy ion collisions

We discuss the interplay between collective flow and density profiles, describing light cluster production in heavy ion collisions at very high energies. Calculations are performed within the coalescence model. We show how collective flow can explain some qualitative features of the measured deuteron spectra, provided a proper parametrization of the spatial dependence of the single particle phase space distribution is chosen.Comment: 11 pages Latex, 2 figures, to be published in Phys. Lett.

Production of Stable and Unstable Nuclei and Hyperfragments in 11.5 A GeV/c Au+Pb collisions

We present measurements of the production of stable light nuclei for mass number A<=7, of strongly decaying states He(5) and Li(5) and of the hypernucleus H(3,lambda). We also examine trends in the production of these multibaryon states as a function of kinematic variables and properties of these states including strangeness content.Comment: Quark Matter '99 Conferenc

Rho meson properties in the Nambu-Jona-Lasinio model

Some properties of the rho vector meson are calculated within the Nambu-Jona-Lasinio model, including processes that go beyond the random phase approximation. To classify the higher order contributions, we adopt $1/N_c$ as expansion parameter. In particular, we evaluate the leading order contributions to the $\rho \rightarrow \pi \pi$ decay width, obtaining the value $\Gamma = 118$ MeV, and to the shift of the rho mass which turns out to be lowered by 64 MeV with respect to its RPA value. A set of model parameters is determined accordingly.Comment: 21 pages Latex, 4 figures, to be published in Z. Phys.

The Transverse Structure of the Baryon Source in Relativistic Heavy Ion Collisions

A direct method to reconstruct the transverse structure of the baryon source formed in a relativistic heavy ion collision is presented. The procedure makes use of experimentally measured proton and deuteron spectra and assumes that deuterons are formed via two-nucleon coalescence. The transverse density shape and flow profile are reconstructed for Pb+Pb collisions at the CERN-SPS. The ambiguity with respect to the source temperature is demonstrated and possible ways to resolve it are discussed.Comment: 15 pages LaTeX, 4 postscript figures, uses psfig.sty - Revised version, few minor change