<p>From Wikipedia, <a href="https://en.wikipedia.org/wiki/Sterile_neutrino" rel="nofollow noreferrer">Sterile neutrino</a></p>
<blockquote>
<p>Particles that possess the quantum numbers of sterile neutrinos and masses great enough such that they do not interfere with the current theory of Big Bang Nucleosynthesis are often called neutral heavy leptons (NHLs) or heavy neutral leptons (HNLs).</p>
</blockquote>
<p>Neutrinos were not expected to possess mass at all, let alone 'great' ones...</p>
<p>The following might provide a clue:</p>
<p>From Wikipedia: <a href="https://en.wikipedia.org/wiki/Liquid_Scintillator_Neutrino_Detector" rel="nofollow noreferrer">Liquid Scintillator Neutrino Detector</a></p>
<blockquote>
<p>Cosmological data bound the mass of the sterile neutrino to ms &lt; 0.26eV (0.44eV) at 95% (99.9%) confidence limit, excluding at high significance the sterile neutrino hypothesis as an explanation of the LSND anomaly.</p>
</blockquote>
<p>Huh?    I am confused...</p>

CC BY-SA 4.0
2021-08-25T07:09:27.740Z
Big bang nucleosynthesis doesn't require sterile neutrinos at all. I am confused by your question. Nor do I follow where you get "neutrinos were not expected to have mass".
ProfRob
CC BY-SA 4.0
2021-08-25T10:33:33.653Z
Neutrinos are required to have non-zero rest-mass, because we observe oscillations between neutrino types and we know that this is only possible with a non-zero rest-mass. Ofc this type of observations doesn't exist for sterile neutrinos, so maybe you want to specify this?
AtmosphericPrisonEscape
CC BY-SA 4.0
2021-08-25T11:10:55.127Z
You should reread the wikipedia article on sterile neutrinos. They are "hypothetical particles" -- in other words, they are beyond the standard model physics. Physicists, astronomers, and cosmologists would love for some indication that the standard model is incomplete, but so far nothing definitive has shown up.
David Hammen
CC BY-SA 4.0
2021-08-25T13:05:12.703Z
@ProfRob - to be fair, neutrinos were considered essentially massless when I was in grad school, before the various measurements of oscillations occurred.
Jon Custer
CC BY-SA 4.0
2021-08-25T13:50:36.450Z
@JohnCuster perhaps true, but oscillation of massive neutrinos were proposed in **1957**, put forward as a solution to the solar neutrino problem in the 70s and experimentally confirmed some 20 years ago.
ProfRob
<observational-astronomy><astrophysics><cosmology><cosmic-microwave-background><neutrinos>
Why does the 'Big Bang Nucleosynthesis' theory require that neutrinos, or at least sterile neutrinos, have a LARGE mass rather than a tiny one?
Kurt Hikes
# Why does the 'Big Bang Nucleosynthesis' theory require that neutrinos, or at least sterile neutrinos, have a LARGE mass rather than a tiny one?

(Asked by: username_0 on 2021-08-25)

From Wikipedia, [Sterile neutrino](https://en.wikipedia.org/wiki/Sterile_neutrino)

> Particles that possess the quantum numbers of sterile neutrinos and masses great enough such that they do not interfere with the current theory of Big Bang Nucleosynthesis are often called neutral heavy leptons (NHLs) or heavy neutral leptons (HNLs).

Neutrinos were not expected to possess mass at all, let alone 'great' ones...

The following might provide a clue:

From Wikipedia: [Liquid Scintillator Neutrino Detector](https://en.wikipedia.org/wiki/Liquid_Scintillator_Neutrino_Detector)

> Cosmological data bound the mass of the sterile neutrino to ms < 0.26eV (0.44eV) at 95% (99.9%) confidence limit, excluding at high significance the sterile neutrino hypothesis as an explanation of the LSND anomaly.

Huh? I am confused...

**Tags:** observational-astronomy, astrophysics, cosmology, cosmic-microwave-background, neutrinos

> **Comments:**
> **username_1**: Big bang nucleosynthesis doesn't require sterile neutrinos at all. I am confused by your question. Nor do I follow where you get "neutrinos were not expected to have mass".  
> **username_2**: Neutrinos are required to have non-zero rest-mass, because we observe oscillations between neutrino types and we know that this is only possible with a non-zero rest-mass. Ofc this type of observations doesn't exist for sterile neutrinos, so maybe you want to specify this?  
> **username_3**: You should reread the wikipedia article on sterile neutrinos. They are "hypothetical particles" -- in other words, they are beyond the standard model physics. Physicists, astronomers, and cosmologists would love for some indication that the standard model is incomplete, but so far nothing definitive has shown up.  
> **username_4**: @username_1 - to be fair, neutrinos were considered essentially massless when I was in grad school, before the various measurements of oscillations occurred.  
> **username_1**: @JohnCuster perhaps true, but oscillation of massive neutrinos were proposed in **1957**, put forward as a solution to the solar neutrino problem in the 70s and experimentally confirmed some 20 years ago.  

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## 0 answers

