Neutrinos penetration of neutron stars or white drawfs

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Discussion Overview

The discussion centers on the penetration of neutrinos through dense astrophysical objects such as neutron stars and white dwarfs. Participants explore the implications of density on neutrino flux reduction and the differences between neutrinos and anti-neutrinos in this context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note that neutrinos can pass through solid objects like Earth with minimal interaction, suggesting a similar behavior in neutron stars and white dwarfs.
  • One participant estimates that neutrinos might penetrate a neutron star by about 10 meters based on the density difference between nuclear and ordinary matter.
  • Another participant references a source indicating that the mean free path of neutrinos in lead is about 22 light years, questioning the linear relationship between density and penetration.
  • There is a query regarding whether neutrinos and anti-neutrinos have the same penetration characteristics.
  • One participant suggests that the interaction rates for neutrinos and anti-neutrinos may differ due to the allowable final states in interactions with nucleons.
  • A later reply challenges the introduction of complexities regarding neutrino and anti-neutrino interactions, emphasizing that the cross-section should account for the density of material without additional complications.

Areas of Agreement / Disagreement

Participants express differing views on the extent of neutrino penetration in neutron stars and the relevance of density in determining this. There is no consensus on the relationship between density and neutrino flux reduction, nor on the implications of neutrino versus anti-neutrino interactions.

Contextual Notes

Participants reference various estimates and sources, but there are unresolved assumptions regarding the linearity of density and penetration, as well as the specifics of neutrino interactions with nucleons.

ensabah6
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Neutrinos can pass through solid objects like the Earth easily, and a light-year of lead would only stop half of them from passing through.

What about something very dense like a white drawf or neutron star? How readily can neutrinos penetrate that? What % flux reduction would be achievable if neutrinos passed through a neutron star?
 
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The density of nuclear matter is greater than the density of ordinary matter by about a factor of 10^15. So I would guess the answer would be that neutrinos would penetrate into a neutron star by roughly (1 light-year)*10^-15=10 m.
 
bcrowell said:
The density of nuclear matter is greater than the density of ordinary matter by about a factor of 10^15. So I would guess the answer would be that neutrinos would penetrate into a neutron star by roughly (1 light-year)*10^-15=10 m.
Is it the same for neutrinos and anti-neutrinos?

Bob S
 
bcrowell said:
The density of nuclear matter is greater than the density of ordinary matter by about a factor of 10^15. So I would guess the answer would be that neutrinos would penetrate into a neutron star by roughly (1 light-year)*10^-15=10 m.

thanks, according to this link it's 22 light years.

Neutrinos
This was an expected result, since the mean free path of a neutrino in matter is about 22 lightyears in lead and having the Earth in the path makes little ...
hyperphysics.phy-astr.gsu.edu/Hbase/particles/neutrino.html

I'm not sure there's a linear proportion of density and penetration.
 
From bcrowell:
The density of nuclear matter is greater than the density of ordinary matter by about a factor of 10^15. So I would guess the answer would be that neutrinos would penetrate into a neutron star by roughly (1 light-year)*10^-15=10 m.

From Bob S
Is it the same for neutrinos and anti-neutrinos?

ensabah6 said:
thanks, according to this link it's 22 light years.

Neutrinos
This was an expected result, since the mean free path of a neutrino in matter is about 22 lightyears in lead and having the Earth in the path makes little ...
hyperphysics.phy-astr.gsu.edu/Hbase/particles/neutrino.html

I'm not sure there's a linear proportion of density and penetration.
I think that a neutrino incident on a neutron has an allowable final state (proton plus electron), while the anti-neutrino incident on a neutron has none. This should be reflected in the total cross section.

Bob S
 
Last edited:
Bob, Bob, Bob...<sigh>

Again, you are adding complications that are unnecessary and confusing.

The cross-section is what it is. If I have 1015 times as much material, the interaction rate goes up by this factor. This is all wrapped into the definition of a cross-section. Talking about the differences between neutrino-on-nucleon and antineutrino-on-nucelon is just muddying the waters.
 

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