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Medium modification of the charged-current neutrino opacity and its implications

Roberts, L. F. and Reddy, Sanjay and Shen, Gang (2012) Medium modification of the charged-current neutrino opacity and its implications. Physical Review C, 86 (6). Art. No. 065803. ISSN 0556-2813.

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Previous work on neutrino emission from proto-neutron stars which employed full solutions of the Boltzmann equation showed that the average energies of emitted electron neutrinos and antineutrinos are closer to one another than predicted by older, more approximate work. This in turn implied that the neutrino driven wind is proton rich during its entire life, precluding r-process nucleosynthesis and the synthesis of Sr, Y, and Zr. This work relied on charged-current neutrino interaction rates that are appropriate for a free nucleon gas. Here, it is shown in detail that the inclusion of the nucleon potential energies and collisional broadening of the response significantly alters this conclusion. Isovector interactions, which give rise to the nuclear symmetry energy, produce a difference between the neutron and proton single-particle energies ΔU=U_n−U_p and alter the kinematics of the charged-current reactions. In neutron-rich matter, and for a given neutrino/antineutrino energy, the rate for ν_e + n → e^− + p is enhanced while ν_e + p → n + e^+ is suppressed because the Q value for these reactions is altered by ±ΔU, respectively. In the neutrino decoupling region, collisional broadening acts to enhance both νe and ν_e cross sections, and random-phase approximation (RPA) corrections decrease the νe cross section and increase the ν_e cross section, but mean field shifts have a larger effect. Therefore, electron neutrinos decouple at lower temperature than when the nucleons are assumed to be free and have lower average energies. The change is large enough to allow for a reasonable period of time when the neutrino driven wind is predicted to be neutron rich. It is also shown that the electron fraction in the wind is influenced by the nuclear symmetry energy.

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Roberts, L. F.0000-0001-7364-7946
Additional Information:© 2012 American Physical Society. Received 18 September 2012; published 14 December 2012. We gratefully acknowledge George Bertsch, Vincenzo Cirigliano, and Stan Woosley for useful discussions concerning this work. We also thank Georg Raffelt for stimulating conversations about neutrino rates in current supernova simulations. L.R. acknowledges support from the University of California Office of the President (09-IR-07-117968-WOOS). His research has also been supported at UCSC by the National Science Foundation (AST-0909129). The work of S.R. was supported by the DOE Grant No. DE-FG02-00ER41132 and by the Topical Collaboration to study Neutrinos and nucleosynthesis in hot dense matter.
Funding AgencyGrant Number
University of California Office of the President09-IR-07-117968-WOOS
Department of Energy (DOE)DE-FG02-00ER41132
Topical CollaborationUNSPECIFIED
Issue or Number:6
Classification Code:PACS: 26.50.+x, 26.60.-c, 21.65.Mn, 95.85.Ry
Record Number:CaltechAUTHORS:20130122-103345383
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Official Citation:Medium modification of the charged-current neutrino opacity and its implications L. F. Roberts, Sanjay Reddy, and Gang Shen Published 14 December 2012 (10 pages) 065803
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36503
Deposited By: Ruth Sustaita
Deposited On:22 Jan 2013 18:54
Last Modified:03 Oct 2019 04:38

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