Neutrino oscillations in dense neutrino gas
Neutrino oscillations in dense neutrino gas
Neutrino flavor oscillations observed by various experiments have led to
the discovery that neutrinos are massive and their vacuum
mass eigenstates are distinct from the flavor states
[1] .
At present, nearly all the mixing parameters have
been measured [2]. However, there remain many unknowns of neutrinos
such as the mass hierarchy, the CP-violating phase(s),
the absolute masses, its Dirac or Majorana nature,
and the possibility of sterile neutrinos (Standard Model singlet)
that may not be easily accessed in terrestrial experiments.
Neutrinos play important roles in the early Universe,
core-collapse supernovae,
and in neutron star-neutron star
or neutron star-black hole mergers. Enormous amount of neutrinos are present
in these environments influencing the physical processes.
Moreover, we may use these
"cosmological and astrophysical laboratories"
to help constrain the fundamental properties of neutrinos.
In order to fully understand the role of neutrinos
in these environments, it is essential to know how
neutrinos change their flavor when large neutrino
fluxes gives rise to the non-linear couplings between
neutrinos with different momenta
[3].
This is a challenging task as it is an intrinsic
many-particle, multi-dimensional, non-equilibrium
quantum problem. Intensive studies of different
groups all over the world has been done in the past decades
(e.g. see
[3]
[4] and the refereces therein).
In our group, we have been working together with our collaborators
to improve the
modelling and understanding of neutrino oscillations in supernovae
and in mergers for the following aspects:
- More consistent inputs from astrophysical simulations:
The collective neutrino flavor oscillations can very
sensitively depend on (i) the competition between the neutrino-neutrino
forward scattering potential and the neutrino-electron potential,
and (ii) the neutrino phase-space distribution functions of all flavors.
In a realistic astrophysical environment, all those quantities
evolve with time. Thus, it is important to perform calculations
with consistent inputs from astrophysical simulations such as
done in [5].
- Coupling flavor oscillations with composition and hydrodynamical
evolution:
If neutrino flavor oscillations happen close enough to their
emission surface, the change of the energy spectra of electron
neutrinos and antineutrinos can cause the change of the composition
and the hydrodynamical qunatities of the surrounding. Interesting
feedbacks/interplays may appear such as shown in [6].
- Physical mechanism governing the flavor oscillations:
Aside from the numerical calculations of neutrino oscillations,
we are also investigating the underlying mechanism that governing
the complicated flavor evolution in these environments. For example,
see [7] for our most recent effort to account for the
"matter neutrino resonances".
All those efforts are toward our final goal of understanding
the role of neutrinos in nucleosynthesis of
heavy elements
and the
supernova explosions.
On top of that, we are also interested in topics
such as exploring the possibility of using neutrino signals to
probe the fundamental properties of neutrinos and
constraining exotic neutrino properties such
as sterile neutrinos, non-standard neutrino interactions
with astrophysical/cosmological models.
References
- [1] 2015 Nobel Prize of physics
- [2] Wiki page of neutrino oscillations
- [3] H. Duan, G. M. Fuller and Y.-Z. Qian, Ann.Rev.Nucl.Part.Sci. 60, 569 (2010), arXiv:1001.2799
- [4] H. Duan, Int. J. Mod. Phys. E24, 1541008 (2015), arXiv:1506.08629
- [5] M.-R. Wu, Y.-Z. Qian, G. Martinez-Pinedo, T. Fischer, L. Huther, Phys. Rev. D91, 065016 (2015), arXiv:1412.8587
- [6] M.-R. Wu, T. Fischer, L. Huther, G. Martinez-Pinedo and Y.-Z. Qian, Phys. Rev. D89, 061303 (2014), arXiv:1305.2382
- [7] M.-R. Wu, H. Duan, and Y.-Z. Qian, arXiv:1509.08975