# Collective neutrino oscillations and neutrino wave packets

## Abstract

Effects of decoherence by wave packet separation on collective neutrino oscillations in dense neutrino gases are considered. We estimate the length of the wave packets of neutrinos produced in core collapse supernovae and the expected neutrino coherence length, and then proceed to consider the decoherence effects within the density matrix formalism of neutrino flavour transitions. First, we demonstrate that for neutrino oscillations in vacuum the decoherence effects are described by a damping term in the equation of motion of the density matrix of a neutrino as a whole (as contrasted to that of the fixed-momentum components of the neutrino density matrix). Next, we consider neutrino oscillations in ordinary matter and dense neutrino backgrounds, both in the adiabatic and non-adiabatic regimes. In the latter case we study two specific models of adiabaticity violation—one with short-term and another with extended non-adiabaticity. It is demonstrated that, while in the adiabatic case a damping term is present in the equation of motion of the neutrino density matrix (just like in the vacuum oscillation case), no such term in general appears in the non-adiabatic regime.

- Authors:

- Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)
- PRISMA Cluster of Excellence and Mainz Institute for Theoretical Physics, Johannes Gutenberg University, 55099 Mainz (Germany)

- Publication Date:

- OSTI Identifier:
- 22667693

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2017; Journal Issue: 09; Other Information: Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; COHERENCE LENGTH; DENSITY; DENSITY MATRIX; EQUATIONS OF MOTION; FLAVOR MODEL; NEUTRINO OSCILLATION; NEUTRINOS; OSCILLATIONS; QUANTUM DECOHERENCE; SUPERNOVAE; VIOLATIONS; WAVE PACKETS

### Citation Formats

```
Akhmedov, Evgeny, Lindner, Manfred, and Kopp, Joachim, E-mail: akhmedov@mpi-hd.mpg.de, E-mail: jkopp@uni-mainz.de, E-mail: lindner@mpi-hd.mpg.de.
```*Collective neutrino oscillations and neutrino wave packets*. United States: N. p., 2017.
Web. doi:10.1088/1475-7516/2017/09/017.

```
Akhmedov, Evgeny, Lindner, Manfred, & Kopp, Joachim, E-mail: akhmedov@mpi-hd.mpg.de, E-mail: jkopp@uni-mainz.de, E-mail: lindner@mpi-hd.mpg.de.
```*Collective neutrino oscillations and neutrino wave packets*. United States. doi:10.1088/1475-7516/2017/09/017.

```
Akhmedov, Evgeny, Lindner, Manfred, and Kopp, Joachim, E-mail: akhmedov@mpi-hd.mpg.de, E-mail: jkopp@uni-mainz.de, E-mail: lindner@mpi-hd.mpg.de. Fri .
"Collective neutrino oscillations and neutrino wave packets". United States. doi:10.1088/1475-7516/2017/09/017.
```

```
@article{osti_22667693,
```

title = {Collective neutrino oscillations and neutrino wave packets},

author = {Akhmedov, Evgeny and Lindner, Manfred and Kopp, Joachim, E-mail: akhmedov@mpi-hd.mpg.de, E-mail: jkopp@uni-mainz.de, E-mail: lindner@mpi-hd.mpg.de},

abstractNote = {Effects of decoherence by wave packet separation on collective neutrino oscillations in dense neutrino gases are considered. We estimate the length of the wave packets of neutrinos produced in core collapse supernovae and the expected neutrino coherence length, and then proceed to consider the decoherence effects within the density matrix formalism of neutrino flavour transitions. First, we demonstrate that for neutrino oscillations in vacuum the decoherence effects are described by a damping term in the equation of motion of the density matrix of a neutrino as a whole (as contrasted to that of the fixed-momentum components of the neutrino density matrix). Next, we consider neutrino oscillations in ordinary matter and dense neutrino backgrounds, both in the adiabatic and non-adiabatic regimes. In the latter case we study two specific models of adiabaticity violation—one with short-term and another with extended non-adiabaticity. It is demonstrated that, while in the adiabatic case a damping term is present in the equation of motion of the neutrino density matrix (just like in the vacuum oscillation case), no such term in general appears in the non-adiabatic regime.},

doi = {10.1088/1475-7516/2017/09/017},

journal = {Journal of Cosmology and Astroparticle Physics},

number = 09,

volume = 2017,

place = {United States},

year = {Fri Sep 01 00:00:00 EDT 2017},

month = {Fri Sep 01 00:00:00 EDT 2017}

}