scholarly journals THE νμ↔νs INTERPRETATION OF THE ATMOSPHERIC NEUTRINO DATA AND COSMOLOGICAL CONSTRAINTS

2000 ◽  
Vol 15 (15) ◽  
pp. 2289-2328 ◽  
Author(s):  
PASQUALE DI BARI ◽  
PAOLO LIPARI ◽  
MAURIZIO LUSIGNOLI
Keyword(s):  
Atmospheric Neutrino ◽  
Big Bang ◽  
Large Contribution ◽  
Atmospheric Neutrinos ◽  
Big Bang Nucleosynthesis ◽  
Potential Conflict ◽  
Lepton Asymmetry ◽  
Cosmological Constraints ◽  
Physical Insight ◽  
Boltzmann Method

The data on atmospheric neutrinos can be explained assuming the existence of oscillations between νμ's and a light sterile neutrino with mixing close to maximal, and δm2~3×10-3 eV 2. This interpretation of the data is in potential conflict with the successes of big bang nucleosynthesis (BBN), since oscillations can result in a too large contribution of the sterile state to the energy density of the universe at the epoch of nucleosynthesis. The possibility to evade these cosmological constraints has been recently the object of some controversy. In this work we rediscuss this problem and find that the inclusion of a small mixing of the sterile state with ντ can result in the generation of a large lepton asymmetry that strongly suppress the νμ↔νs oscillations eliminating the possible conflict with BBN bounds. In this scheme the mass of the tau neutrino must be larger than few eV's and is compatible with cosmological bounds. Our calculations are performed using a Pauli–Boltzmann method. In this approach it is also possible to develop analytic calculations that allow physical insight in the processes considered and give support to the numerical results.

scholarly journals Neutrino oscillations and the early universe

Open Physics ◽  
2004 ◽  
Vol 2 (3) ◽  
Author(s):  
Daniela Kirilova
Keyword(s):  
Early Universe ◽  
Neutrino Oscillation ◽  
Neutrino Oscillations ◽  
Atmospheric Neutrino ◽  
Short Review ◽  
Big Bang ◽  
Big Bang Nucleosynthesis ◽  
Cosmological Constraints ◽  
Theoretical Status

AbstractThe observational and theoretical status of neutrino oscillations in connection with solar and atmospheric neutrino anomalies is presented briefly. The effect of neutrino oscillations on the evolution of the early Universe is discussed in detail. A short review is given of the standard Big Bang Nucleosynthesis (BBN) and the influence of resonant and non-resonant neutrino oscillations on active neutrinos and on primordial synthesis of He-4. BBN cosmological constraints on neutrino oscillation parameters are discussed.

scholarly journals Lepton asymmetry, neutrino spectral distortions, and big bang nucleosynthesis

2017 ◽  
Vol 95 (6) ◽  
Author(s):  
E. Grohs ◽  
George M. Fuller ◽  
C. T. Kishimoto ◽  
Mark W. Paris
Keyword(s):  
Big Bang ◽  
Big Bang Nucleosynthesis ◽  
Lepton Asymmetry

scholarly journals NEUTRINO SPECTRUM DISTORTION DUE TO OSCILLATIONS AND ITS BBN EFFECT

2004 ◽  
Vol 13 (05) ◽  
pp. 831-841 ◽  
Author(s):  
DANIELA KIRILOVA
Keyword(s):  
Sterile Neutrino ◽  
Big Bang ◽  
Neutrino Energy ◽  
Electron Neutrino ◽  
Initial Population ◽  
Neutrino Mixing ◽  
Big Bang Nucleosynthesis ◽  
Cosmological Constraints ◽  
Neutrino Spectrum ◽  
Primordial Abundance

We study the distortion of electron neutrino energy spectrum due to oscillations with the sterile neutrino νe↔νs, for different initial populations of the sterile state δNs at the onset of oscillations. The influence of this spectrum distortion on Big Bang Nucleosynthesis is analyzed. Only the case of an initially empty sterile state was studied in previous publications. The primordial abundance of 4He is calculated for all possible δNs:0≤δNs≤1 in the model of oscillations, effective after electron neutrino decoupling, for which the spectrum distortion effects on the neutron–proton transitions are the strongest. It is found that the spectrum distortion effect may be dominant, not only in the case of small δNs, but also in the case of large initial population of νs. For example, in the resonant case it may play a considerable role even for very large δNs~0.8. Cosmological constraints on neutrino mixing for small δNs are discussed.

scholarly journals THE STATUS OF NEUTRINO MASS

1998 ◽  
Vol 13 (25) ◽  
pp. 4409-4423 ◽  
Author(s):  
DAVID O. CALDWELL
Keyword(s):  
Dark Matter ◽  
Neutrino Mass ◽  
Heavy Element ◽  
Sterile Neutrino ◽  
Big Bang ◽  
Atmospheric Neutrinos ◽  
Big Bang Nucleosynthesis ◽  
Robust Solution ◽  
The Status ◽  
Mass Pattern

New experimental results, if correct, require at least one light sterile neutrino, in addition to the three active ones, to accommodate the mass differences required to explain the solar νe deficit, the anomalous μ/e ratio produced by atmospheric neutrinos, and either the candidate events for νμ→ νe (or [Formula: see text]) from the LSND experiment, or the possible need for a hot component of dark matter. This neutrino mass pattern can not only accommodate all these four requirements, but also provide a robust solution to a problem presently making heavy-element synthesis by supernovae impossible and resolve a possible discrepancy between big bang nucleosynthesis theory and observations.

scholarly journals Big Bang Nucleosynthesis and Lepton Number Asymmetry in the Universe

1999 ◽  
Vol 183 ◽  
pp. 312-312
Author(s):  
K. Kohri ◽  
M. Kawasaki ◽  
Katsuhiko Sato
Keyword(s):  
Chemical Potential ◽  
High Redshift ◽  
Big Bang ◽  
Electron Neutrino ◽  
Light Elements ◽  
Big Bang Nucleosynthesis ◽  
Lepton Asymmetry ◽  
Stringent Constraint ◽  
Likelihood Analysis ◽  
The Universe

Recently it has been reported that there may be a discrepancy between big bang nucleosynthesis theory and observations (BBN crisis) (Hata et al., 1995). One way to solve the discrepancy might be to adopt some modifications of standard physics used in SBBN (Kawasaki et al, 1997). We show that BBN predictions agree with the primordial abundances of light elements, 4He, D, 3He and 7Li inferred from the observational data if the electron neutrino has a net chemical potential ξve due to lepton asymmetry (Kohri et al., 1997). We study BBN with the effects of the neutrino degeneracy in details using Monte Carlo simulation and make a likelihood analysis using the most recent data. We estimate that (95% C.L.) and (95% C.L.) adopting the presolar Deuterium abundance as the primordial values. If we adopted the low D abundance which is obtained by the observation of the high redshift QSO absorption systems, (95% C.L.) and The estimated chemical potential of ve is about 10−5 eV which is much smaller than experiments can detect (≃ 1 eV). In other words, BBN gives the most stringent constraint on the chemical potential of ve.

scholarly journals Big bang nucleosynthesis constraints on sterile neutrino and lepton asymmetry of the Universe

2020 ◽  
Vol 2020 (09) ◽  
pp. 051-051 ◽  
Author(s):  
Graciela B. Gelmini ◽  
Masahiro Kawasaki ◽  
Alexander Kusenko ◽  
Kai Murai ◽  
Volodymyr Takhistov
Keyword(s):  
Sterile Neutrino ◽  
Big Bang ◽  
Big Bang Nucleosynthesis ◽  
Lepton Asymmetry ◽  
The Universe

scholarly journals Neutrinos and Big Bang Nucleosynthesis

2012 ◽  
Vol 2012 ◽  
pp. 1-24 ◽  
Author(s):  
Gary Steigman
Keyword(s):  
Particle Physics ◽  
Weak Interactions ◽  
Big Bang ◽  
Baryon Density ◽  
Big Bang Nucleosynthesis ◽  
Lepton Asymmetry ◽  
Lithium Abundance ◽  
Dark Radiation ◽  
Cosmic Neutrino Background ◽  
Neutrino Background

According to the standard models of particle physics and cosmology, there should be a background of cosmic neutrinos in the present Universe, similar to the cosmic microwave photon background. The weakness of the weak interactions renders this neutrino background undetectable with current technology. The cosmic neutrino background can, however, be probed indirectly through its cosmological effects on big bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) radiation. In this BBN review, focused on neutrinos and more generally on dark radiation, the BBN constraints on the number of “equivalent neutrinos” (dark radiation), on the baryon asymmetry (baryon density), and on a possible lepton asymmetry (neutrino degeneracy) are reviewed and updated. The BBN constraints on dark radiation and on the baryon density following from considerations of the primordial abundances of deuterium and helium-4 are in excellent agreement with the complementary results from the CMB, providing a suggestive, but currently inconclusive, hint of the presence of dark radiation, and they constrain any lepton asymmetry. For all the cases considered here there is a “lithium problem”: the BBN-predicted lithium abundance exceeds the observationally inferred primordial value by a factor of~3.

scholarly journals BBN CONSTRAINTS ON NEUTRINO OSCILLATIONS PARAMETERS RELAXED OR STRENGTHENED

2007 ◽  
Vol 16 (07) ◽  
pp. 1197-1210 ◽  
Author(s):  
DANIELA KIRILOVA
Keyword(s):  
Energy Spectrum ◽  
Energy Density ◽  
Sterile Neutrino ◽  
Full Range ◽  
Big Bang ◽  
The Other ◽  
Big Bang Nucleosynthesis ◽  
Cosmic Expansion ◽  
Cosmological Constraints ◽  
Kinetic Effects

Big Bang Nucleosynthesis (BBN) with nonequilibrium νe ↔ νs oscillations, in the more general case of non-zero population of νs before oscillations δNs ≠ 0, is discussed. 4 He primordial production Yp(δNs) in the presence of νe ↔ νs oscillations for different initial populations of the sterile neutrino state 0 ≤ δ Ns ≤ 1 and the full range of oscillation parameters is calculated. Non-zero δNs has a two-fold effect on 4 He : (i) it enhances the energy density and hence increases the cosmic expansion rate, leading to Ypoverproduction, and (ii) it suppresses the kinetic effects of oscillations on BBN, namely, the effects on pre-BBN nucleon kinetics, caused by the νe energy spectrum distortion and the [Formula: see text] asymmetry generation by oscillations, leading to decreased Yp production. Depending on oscillation parameters one or the other effect may dominate, causing, correspondingly, either a relaxation of the cosmological constraints or their strengthening with the increase of δNs. More general BBN constraints on νe ↔ νs oscillation parameters, corresponding to 3% Yp overproduction, for different initial populations of the sterile state are calculated. Previous BBN constraints were derived assuming empty sterile state before oscillations. It is shown that the cosmological constraints strengthen with the increase of δNs value, the change being more considerable for nonresonant oscillations.

scholarly journals MeV-scale seesaw and leptogenesis

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Valerie Domcke ◽  
Marco Drewes ◽  
Marco Hufnagel ◽  
Michele Lucente
Keyword(s):  
Parameter Space ◽  
Pion Mass ◽  
Mass Range ◽  
Big Bang ◽  
Neutrino Masses ◽  
Type I ◽  
Big Bang Nucleosynthesis ◽  
Cosmological Constraints ◽  
The Universe ◽  
Rule Out

Abstract We study the type-I seesaw model with three right-handed neutrinos and Majorana masses below the pion mass. In this mass range, the model parameter space is not only strongly constrained by the requirement to explain the light neutrino masses, but also by experimental searches and cosmological considerations. In the existing literature, three disjoint regions of potentially viable parameter space have been identified. In one of them, all heavy neutrinos decay shortly before big bang nucleosynthesis. In the other two regions, one of the heavy neutrinos either decays between BBN and the CMB decoupling or is quasi-stable. We show that previously unaccounted constraints from photodisintegration of nuclei practically rule out all relevant decays that happen between BBN and the CMB decoupling. Quite remarkably, if all heavy neutrinos decay before BBN, the baryon asymmetry of the universe can be quite generically explained by low-scale leptogenesis, i.e. without further tuning in addition to what is needed to avoid experimental and cosmological constraints. This motivates searches for heavy neutrinos in pion decay experiments.

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