38257375
Prospects for detection of a cosmologically significant neutrino mass from a galactic supernova neutrino burst using a neutral-current-based detector.
Author(s): Cline, DB; Fuller, GM; Hong, WP; Meyer, B; Wilson, J | Abstract: We discuss how proposed supernova neutrino detectors could measure masses for or neutrinos in the range of 15 to 50 eV. The range for measurable masses might be extended down to 5 eV, depending on our confidence in some of the predicted features of the supernova-neutrino-burst signal. We discuss the expected characteristics of supernova neutrino signals in proposed neutral-current-based detectors. © 1994 The American Physical Society.
14018179
Evolution of massive stars up to the end of central oxygen burning
We present a detailed study of the evolution of massive stars of masses 15, 20, 25, and 30 M☉ assuming solar-like initial chemical composition. The stellar sequences were evolved through the advanced burning phases up to the end of core oxygen burning. We present a careful analysis of the physical characteristics of the stellar models. In particular, we investigate the effect of the still-unsettled reaction 12C(α,γ)16O on the advanced evolution by using recent compilations of this rate. We find that this rate has a significant impact on the evolution not only during the core helium burning phase but also during the late burning phases, especially the shell carbon burning. We have also considered the effect of different treatments of convective instability based on the Ledoux criterion in regions of varying molecular weight gradient during the hydrogen- and helium-burning phases. We compare our results with other investigations whenever available. Finally, our present study constitutes the basis of analyzing the nucleosynthesis processes in massive stars. In particular, we will present a detailed analysis of the s-process in a forthcoming paper.
53066200
Source of the Rare-Earth Element Peak in r-Process Nucleosynthesis
We use network calculations of r -process nucleosynthesis to pin down the origin of the peak in the solar r -process abundance distribution near nuclear mass number A{approx}160 . The peak is due to a subtle interplay of nuclear deformation and {beta} decay, and forms not in the steady phase of the r process, but only just prior to freeze-out, as the free neutrons rapidly disappear. Its existence should therefore help constrain the conditions under which the r process freezes out. {copyright} {ital 1997} {ital The American Physical Society}
121834079
General constraints on the age and chemical evolution of the Galaxy
The formalism of Schramm and Wasserburg (1970) for determining the mean age of the elements is extended. Model-independent constraints (constraints that are independent of a specific form for the effective nucleosynthesis rate and Galactic chemical evolution over time) are derived on the first four terms in the expansion giving the mean age of the elements, and from these constraints limits are derived on the total duration of nucleosynthesis. These limits require only input of the Schramm-Wasserburg parameter ..delta../sup max/ and of the ratio of the mean time for formation of the elements to the total duration of nucleosynthesis, t/sub nu//T. The former quantity is a function of nuclear input parameters. Limits on the latter are obtained from constraints on the relative rate of nucleosynthesis derived from the /sup 232/Th//sup 238/U, /sup 235/U//sup 238/U, and shorter-lived chronometric pairs. 65 refs.
120235748
Neutrino capture and r-process nucleosynthesis
Neutrino capture effects on free nucleons and heavy nuclei in r-process nucleosynthesis are discussed. Neutrino capture on heavy nuclei can “accelerate” the r-process; however, the dominant role neutrino capture plays is to set the neutron-to-proton ratio. In fact, network calculations indicate that neutrino capture on heavy nuclei is unlikely to be significant for r-process components that produce nuclei with mass number A near 195. The reason is that if the neutrino flux is sufficiently large to cause neutrino capture on heavy nuclei to be important, it was even larger in a earlier phase when 4He and neutrons dominated the abundances and capture on the free neutrons drastically reduced the neutron-to-seed-nucleus ratio.
121296909
MUONS PRODUCED BY ATMOSPHERIC NEUTRINOS: EXPERIMENT.
46004879
Experimental study of muon bundles observed in the Fréjus detector.
The present study is based on a sample of 407 775 single muons and 12 559 muon bundles with zenith angles smaller than 60{degree}, observed in the 12.3 m{times}6 m{times}6 m Frejus proton-decay detector, at a depth of 4850 hg/cm{sup 2}. The variation of the vertical muon intensity with depth is given. Using a maximum-likelihood method, the muon lateral distribution of underground bundles is investigated as a function of muon multiplicity and zenith angle. The same method yields the true multiplicity distribution at the site depth, corrected for all detection effects.
2491512
Space-time as a causal set.
We propose that space-time at the smallest scales is in reality a causal set: a locally finite set of elements endowed with a partial order corresponding to the macroscopic relation that defines past and future. We explore how a Lorentzian manifold can approximate a causal set, noting in particular that the thereby defined effective dimensionality of a given causal set can vary with length scale. Finally, we speculate briefly on the quantum dynamics of causal sets, indicating why an appropriate choice of action can reproduce general relativity in the classical limit.