Color-Flavor (Un)locking

The structure of the phase diagram of strongly interacting matter at moderate densities is calculated within a 3-flavor NJL-type quark model with realistic quark masses. We focus on the influence of the selfconsistently determined effective strange quark mass on the color-flavor unlocking phase transition.Comment: To appear in the proceedings of the workshop "Ultrarelativistic heavy ion collisions", Hirschegg 2002, 6 page

Color superconductivity in two- and three-flavor systems at moderate densities

Basic features of color superconductivity are reviewed, focusing on the regime of ``moderate densities'', which is not accessible by perturbation theory. We discuss the standard picture of two- and three flavor color superconductors and study the color-flavor unlocking phase transition within an NJL-type model.Comment: 12 pages, 7 figures, to appear in: Proceedings of the NATO Advanced Research Workshop on Confinement, Topology, and other Non-Perturbative Aspects of QCD, Stara Lesna, Slovakia, Jan 21-27, 2002, references adde

Color-Flavor Unlocking and Phase Diagram with Self-Consistently Determined Strange Quark Masses

The phase diagram of strongly interacting matter at non-zero temperature and baryon chemical potential is calculated within a 3-flavor NJL-type quark model with realistic quark masses. The model exhibits spontaneous chiral symmetry breaking as well as diquark condensation in the two-flavor color-superconducting phase and in the color-flavor locked phase. We investigate the color-flavor unlocking phase transition, taking into account self-consistently calculated effective quark masses. We find that it is mainly triggered by a first order phase transition with respect to the strange quark mass. It takes place at much higher values of the chemical potential than the transition to the hadronic phase such that we find a relatively large region in the phase diagram where the two-flavor color-superconductor seems to be the most favored state.Comment: 16 pages, 5 figures; v2: figure 2 of v1 removed, some changes in the discussion, references adde

A consistent approximation scheme beyond RPA for bosons

In this paper, we develop a consistent extension of RPA for bosonic systems. In order to illustrate the method, we consider the case of the anharmonic oscillator. We compare our results with those obtained in mean-field and standard RPA approaches, with the exact ones and show that they are very close to the exact ones.Comment: 19 pages, Latex, 1 figure, accepted version in EPJ

Measurement of time differences between luminous events Patent

Mechanism for measuring nanosecond time differences between luminous events using streak camer

Thermodynamics of baryonic matter with strangeness within non-relativistic energy density functional model

We study the thermodynamical properties of compressed baryonic matter with strangeness within non-relativistic energy density functional models with a particular emphasis on possible phase transitions found earlier for a simple $n,p,e,\Lambda$-mixture. The aim of the paper is twofold: I) examining the phase structure of the complete system, including the full baryonic octet and II) testing the sensitivity of the results to the model parameters. We find that, associated to the onset of the different hyperonic families, up to three separate strangeness-driven phase transitions may occur. Consequently, a large fraction of the baryonic density domain is covered by phase coexistence with potential relevance for (proto)-neutron star evolution. It is shown that the presence of a phase transition is compatible both with the observational constraint on the maximal neutron star mass, and with the present experimental information on hypernuclei. In particular we show that two solar mass neutron stars are compatible with important hyperon content. Still, the parameter space is too large to give a definitive conclusion of the possible occurrence of a strangeness driven phase transition, and further constraints from multiple-hyperon nuclei and/or hyperon diffusion data are needed.Comment: 11 pages, 7 figure

Modification of magicity towards the dripline and its impact on electron-capture rates for stellar core-collapse

The importance of microphysical inputs from laboratory nuclear experiments and theoretical nuclear structure calculations in the understanding of the core collapse dynamics, and the subsequent supernova explosion, is largely recognized in the recent literature. In this work, we analyze the impact of the masses of very neutron rich nuclei on the matter composition during collapse, and the corresponding electron capture rate. To this aim, we introduce an empirical modification of the popular Duflo-Zuker mass model to account for possible shell quenching far from stability, and study the effect of the quenching on the average electron capture rate. We show that the preeminence of the $N=50$ and $N=82$ closed shells in the collapse dynamics is considerably decreased if the shell gaps are reduced in the region of $^{78}$Ni and beyond. As a consequence, local modifications of the overall electron capture rate up to 30\% can be expected, with integrated values strongly dependent on the stiffness of magicity quenching and progenitor mass and potential important consequences on the entropy generation, the neutrino emissivity, and the mass of the core at bounce. Our work underlines the importance of new experimental measurements in this region of the nuclear chart, the most crucial information being the nuclear mass and the Gamow-Teller strength. Reliable microscopic calculations of the associated elementary rate, in a wide range of temperatures and electron densities, optimized on these new empirical information, will be additionally needed to get quantitative predictions of the collapse dynamics.Comment: 12 pages, 10 figure

How to preserve symmetries with cut-off regularized integrals?

We present a prescription to calculate the quadratic and logarithmic divergent parts of several integrals employing a cutoff in a coherent way, i.e. in total agreement with symmetry requirements. As examples we consider one-loop Ward identities for QED and a phenomenological chiral model.Comment: 11 pages, 3 graph

Tests of non-standard electroweak couplings of right-handed quarks

The standard model can be interpreted as the leading order of a Low-Energy Effective Theory (LEET) invariant under a higher non linearly realized symmetry $S_{nat}\supset SU(2)_W \times U(1)_Y$ equipped with a systematic power counting. Within the minimal version of this ``not quite decoupling'' LEET, the dominant non-standard effect appears at next-to-leading order (NLO) and is a modification of the couplings of fermions to W and Z. In particular, the coupling of right-handed quarks to Z is modified and a direct coupling of right-handed quarks to W emerges. Charged right-handed lepton currents are forbidden by an additional discrete symmetry in the lepton sector originally designed to suppress Dirac neutrino masses. A complete NLO analysis of experimental constraints on these modified couplings is presented. Concerning couplings of light quarks, the interface of the electroweak tests with QCD aspects is discussed in detail.Comment: 56 pages, 14 figures, v2: references added, minor modifications in the text, accepted for publication in JHE

Particle size distribution of suspended solids in the Chesapeake Bay entrance and adjacent shelf waters

Characteristics of suspended solids, including total suspended matter, total suspended inorganics, total suspended organics, particle size distribution, and the presence of the ten most prominent particle types were determined. Four research vessels simultaneously collected samples along four transects. Samples were collected within a 2-hour period that coincided with the maximum ebb penetration of Chesapeake Bay outwelling. The distribution of primary and secondary particle size modes indicate the presence of a surface or near-surface plume, possibly associated with three sources: (1) runoff, (2) resuspension of material within the Bay, and/or (3) resuspension of material in the area of shoals at the Bay mouth. Additional supportive evidence for this conclusion is illustrated with ocean color scanner data