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During the collapse of a massive star{close_quote}s stellar core Coulomb effects maintain the ions in a highly correlated state. This has an important consequence: Neutrino-nucleus elastic scattering, which dominates the neutrino opacity, is substantially reduced for low-energy neutrinos. This results from phase interference effects that occur when the neutrino wavelength becomes larger than the interion spacing, and is analogous to a crystal becoming transparent to x rays when the change in wave number from scattering is smaller than the reciprocal lattice spacing. This reduction in the neutrino-nucleus elastic scattering cross section, referred to as {open_quotes}ion screening,{close_quotes} has been calculated most recently by Horowitz. Using his correction, we investigate its effect on stellar core collapse. Our numerical results show that {nu}{sub e} downscattering with electrons is sufficiently rapid to fill the low-energy neutrino window created by ion screening, but the window width is insufficient for ion screening to have a significant effect on core deleptonization. In particular, inclusion of ion screening lowers the trapped lepton fraction by only 0.015 in both our 15M{sub {circle_dot}} and a 25M{sub {circle_dot}} models. We confirm this with an analytic model that elucidates ion screening{close_quote}s essential effect. For the sake of comparison, we also investigate the effect on core deleptonization of turning neutrino-nucleus elastic scattering off completely, and of turning off all semileptonic neutral-current neutrino scattering. These latter neutrino opacity modifications have substantially greater effects on core deleptonization than the ion-screening correction. {copyright} {ital 1997} {ital The American Physical Society}
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| Authors: |
Bruenn, S.W. [Department of Physics, Florida Atlantic University, Boca Raton, Florida 33431-0991 (United States)];
Mezzacappa, A. [Theoretical and Computational Physics Group, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6354 (United States)]
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| Publication Date: | 1997 Dec 01 |
| OSTI Identifier: | 554428 |
| DOE Contract Number: | AC05-96OR22464 |
| Resource Type: | Journal Article |
| Resource Relation: | Journal Name: Physical Review, D; Journal Volume: 56; Journal Issue: 12; Other Information: PBD: Dec 1997 |
| Research Org: | Oak Ridge National Laboratory |
| Country of Publication: | United States |
| Language: | English |
| Format: | Size: pp. 7529-7547 |
| Other Number(s): | Journal ID: PRVDAQ; ISSN 0556-2821; TRN: 98:002046 |
| Subject: | 66 PHYSICS; GRAVITATIONAL COLLAPSE; STELLAR ACTIVITY; IONS; SCREENING; NEUTRINOS; OPACITY; NEUTRINO REACTIONS; ELASTIC SCATTERING; INTERFERENCE; WAVELENGTHS; CROSS SECTIONS; NEUTRAL CURRENTS |
| Update Date: | 2009 Dec 16 |
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