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Title: Non equilibrium dynamics of mixing, oscillations, and equilibration: A model study

Abstract

The non-equilibrium dynamics of mixing, oscillations and equilibration is studied in a field theory of flavored neutral mesons that effectively models two flavors of mixed neutrinos, in interaction with other mesons that represent a thermal bath of hadrons or quarks and charged leptons. This model describes the general features of neutrino mixing and relaxation via charged currents in a medium. The reduced density matrix and the non-equilibrium effective action that describes the propagation of neutrinos is obtained by integrating out the bath degrees of freedom. We obtain the dispersion relations, mixing angles and relaxation rates of ``neutrino'' quasiparticles. The dispersion relations and mixing angles are of the same form as those of neutrinos in the medium, and the relaxation rates are given by $$\Gamma_1(k) = \Gamma_{ee}(k) \cos^2\theta_m(k)+\Gamma_{\mu\mu}(k)\sin^2\theta_m(k); \Gamma_2(k)= \Gamma_{\mu\mu}(k) \cos^2\theta_m(k)+\Gamma_{ee}(k)\sin^2\theta_m(k) $$ where $$\Gamma_{\alpha\alpha}(k)$$ are the relaxation rates of the flavor fields in \emph{absence} of mixing, and $$\theta_m(k)$$ is the mixing angle in the medium. A Weisskopf-Wigner approximation that describes the asymptotic time evolution in terms of a non-hermitian Hamiltonian is derived. At long time $$>>\Gamma^{-1}_{1,2}$$ ``neutrinos'' equilibrate with the bath. The equilibrium density matrix is nearly diagonal in the basis of eigenstates of an \emph{effective Hamiltonian that includes self-energy corrections in the medium}. The equilibration of ``sterile neutrinos'' via active-sterile mixing is discussed.

Authors:
; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
Physics Division
OSTI Identifier:
934708
Report Number(s):
LBNL-416E
TRN: US0803840
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review D; Journal Volume: 75; Related Information: Journal Publication Date: 12 April 2007
Country of Publication:
United States
Language:
English
Subject:
72; APPROXIMATIONS; CHARGED CURRENTS; DEGREES OF FREEDOM; DENSITY MATRIX; DISPERSION RELATIONS; EIGENSTATES; HADRONS; HAMILTONIANS; LEPTONS; MESONS; NEUTRINOS; OSCILLATIONS; QUARKS; RELAXATION; SELF-ENERGY; neutrino, mixing angle; neutrino, oscillation; meson, interaction; charged current; density matrix, reduced; effective action; dispersion relations; neutrino, quasiparticle; neutrino, width; effective Hamiltonian; Langevin equation, solution; correlation function

Citation Formats

Ho, Chiu Man, Boyanovsky, D., and Ho, C. M. Non equilibrium dynamics of mixing, oscillations, and equilibration: A model study. United States: N. p., 2006. Web.
Ho, Chiu Man, Boyanovsky, D., & Ho, C. M. Non equilibrium dynamics of mixing, oscillations, and equilibration: A model study. United States.
Ho, Chiu Man, Boyanovsky, D., and Ho, C. M. Fri . "Non equilibrium dynamics of mixing, oscillations, and equilibration: A model study". United States. doi:. https://www.osti.gov/servlets/purl/934708.
@article{osti_934708,
title = {Non equilibrium dynamics of mixing, oscillations, and equilibration: A model study},
author = {Ho, Chiu Man and Boyanovsky, D. and Ho, C. M.},
abstractNote = {The non-equilibrium dynamics of mixing, oscillations and equilibration is studied in a field theory of flavored neutral mesons that effectively models two flavors of mixed neutrinos, in interaction with other mesons that represent a thermal bath of hadrons or quarks and charged leptons. This model describes the general features of neutrino mixing and relaxation via charged currents in a medium. The reduced density matrix and the non-equilibrium effective action that describes the propagation of neutrinos is obtained by integrating out the bath degrees of freedom. We obtain the dispersion relations, mixing angles and relaxation rates of ``neutrino'' quasiparticles. The dispersion relations and mixing angles are of the same form as those of neutrinos in the medium, and the relaxation rates are given by $\Gamma_1(k) = \Gamma_{ee}(k) \cos^2\theta_m(k)+\Gamma_{\mu\mu}(k)\sin^2\theta_m(k); \Gamma_2(k)= \Gamma_{\mu\mu}(k) \cos^2\theta_m(k)+\Gamma_{ee}(k)\sin^2\theta_m(k) $ where $\Gamma_{\alpha\alpha}(k)$ are the relaxation rates of the flavor fields in \emph{absence} of mixing, and $\theta_m(k)$ is the mixing angle in the medium. A Weisskopf-Wigner approximation that describes the asymptotic time evolution in terms of a non-hermitian Hamiltonian is derived. At long time $>>\Gamma^{-1}_{1,2}$ ``neutrinos'' equilibrate with the bath. The equilibrium density matrix is nearly diagonal in the basis of eigenstates of an \emph{effective Hamiltonian that includes self-energy corrections in the medium}. The equilibration of ``sterile neutrinos'' via active-sterile mixing is discussed.},
doi = {},
journal = {Physical Review D},
number = ,
volume = 75,
place = {United States},
year = {Fri Dec 22 00:00:00 EST 2006},
month = {Fri Dec 22 00:00:00 EST 2006}
}