45,320 research outputs found

    The prompt lepton cookbook

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    We review the calculation of the prompt lepton flux, produced in the atmosphere by the semileptonic decay of charmed particles. We describe side by side the intermediary ingredients used by different authors, which include not only the charm production model, but also other atmospheric particle showering parameters. After evaluating separately the relevance of each single ingredient, we analyze the effect of different combinations over the final result. We highlight the impact of the prompt lepton flux calculation upon high-energy neutrino telescopes.Comment: 21 pages, 10 figures; revised version, accepted for publication in Astroparticle Physic

    Nucleosynthesis in Fast Expansions of High-Entropy, Proton Rich Matter

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    We demonstrate that nucleosynthesis in rapid, high-entropy expansions of proton-rich matter from high temperature and density can result in a wider variety of abundance patterns than heretofore appreciated. In particular, such expansions can produce iron-group nuclides, p-process nuclei, or even heavy, neutron-rich isotopes. Such diversity arises because the nucleosynthesis enters a little explored regime in which the free nucleons are not in equilibrium with the abundant alpha particles. This allows nuclei significantly heavier than iron to form in t he presence of abundant free nucleons early in the expansion. As the temperature drops, nucleons increasingly assemble into alpha particles and heavier nuclei. If the assembly is efficient, the resulting depletion of free neutrons allows disintegrat ion flows to drive nuclei back down to iron and nickel. If this assembly is inefficient, then the large abundance of free nucleons prevents the disintegration flows and leaves a distribution of heavy nuclei after reaction freezeout. For cases in between, an intermediate abundance distribution, enriched in p-process isotopes, is frozen out. These last expansions may contribute to the solar system's supply of the p-process nuclides if mildly proton-rich, high-entropy matter is ejected from proto-neutron stars winds or other astrophysical sites. Also sign ificant is the fact that, because the nucleosynthesis is primary, the signature of this nucleosyn thesis may be evident in metal poor stars.Comment: 11 pages, 2 tables, 1 figure. Submitted to ApJ Letter

    Reconstruction of Quark Mass Matrices with Weak Basis Texture Zeroes from Experimental Input

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    All quark mass matrices with texture zeroes obtained through weak basis transformations are confronted with the experimental data. The reconstruction of the quark mass matrices M_u and M_d at the electroweak scale is performed in a weak basis where the matrices are Hermitian and have a maximum of three vanishing elements. The same procedure is also accomplished for the Yukawa coupling matrices at the grand unification scale in the context of the Standard Model and its minimal supersymmetric extension as well as of the two Higgs doublet model. The analysis of all viable power structures on the quark Yukawa coupling matrices that could naturally appear from a Froggatt-Nielsen mechanism is also presented.Comment: RevTeX4, 3 tables, 21 pages; misprints corrected and one reference adde
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