Consequences of a fourth neutrino type

In summary, if there was a fourth neutrino type, it would have affected the universe's development in a way that more photons and He-4 were produced, less photons and He-4 were produced, more neutrons and He-4 were produced, or more protons and He-4 were produced.
  • #1
szcsongor
3
0
Homework Statement
If there was a fourth neutrino type it would have affected Universe's development the following way...
Relevant Equations
none
Hi,

I got this question on a recent astronomy course but can't really find the right answer (rough translation from Swedish):

If there was a fourth neutrino type it would have affected Universe's development the following way:
a. more photons and more He-4 generated
b. less photons and less He-4
c. more neutrons and more He-4
d. more protons and more He-4

My guess would be answer (a) but I'm not sure.
 
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  • #2
Relevant Equations
none
Are you sure you don't have equations describing the evolution of the early universe? How does its temperature change over time? How does that depend on neutrinos?
szcsongor said:
My guess would be answer (a) but I'm not sure.
Why do you guess (a)?
 
  • #3
Hi,

Thanks for the quick reply. I was on holiday, so couldn't answer sooner.
I was thinking about this question but unfortunately I don't know how to start solving it. I guess there are some relations (equations?) to use here but I'm unable to see it :(

The temperature of the universe is decreasing constantly, but I don't see the relation with neutrinos.
My guess was a) because I was thinking that neutrinos are produced in the process of H-1 -> He-4 alongside with photons, so another type of neutrinos could be a consequence of more He-4 and photons produced. But it might be true only in stars... Or might be that I'm wrong completely :)
 
  • #4
Think earlier. How did neutrinos influence the temperature evolution?
Electron neutrinos were important for the neutron to proton ratio, but a fourth generation neutrino shouldn't affect that directly as it doesn't couple to electrons.

If you prefer you can also look up how Planck measured the number of neutrino generations in the early universe. Their result was 3...
 
  • #5
Thanks for trying to help.
I think I see now how I should proceed with this. I also found clues in the course material now when I read through it:

If we "put in" an other type of neutrino into the universe there should be less baryonic matter to comply with the principle of conservation of mass. But since neutrinos do not interact with matter (and also almost massless), the universe would have expanded faster. The consequence would have been more neutrons (higher neutron / proton ratio) because there would have been less time for the n -> p + e + v reaction. And more neutrons mean more He-4 generated. Therefore answer (c) seem to be the right one.
Am I right? :)
 
  • #6
Sounds plausible.
 

1. What is a fourth neutrino type?

A neutrino is a subatomic particle that has very little mass and no electric charge. It is one of the fundamental particles that make up the universe. Currently, there are three known types of neutrinos: electron, muon, and tau. A fourth neutrino type refers to a hypothetical fourth type of neutrino that has not yet been discovered.

2. What are the potential consequences of a fourth neutrino type?

If a fourth neutrino type is discovered, it could have significant implications for our understanding of particle physics and the Standard Model. It could also help explain some of the mysteries of the universe, such as the origin of dark matter and the matter-antimatter asymmetry problem.

3. How would a fourth neutrino type be detected?

Scientists are currently using various methods to search for evidence of a fourth neutrino type. These include experiments at particle accelerators, underground detectors, and studying the behavior of neutrinos from cosmic sources. If a fourth neutrino type exists, it is expected to interact differently with matter and have a unique signature that can be detected.

4. What are the challenges in proving the existence of a fourth neutrino type?

The biggest challenge in proving the existence of a fourth neutrino type is that it is a very elusive particle and interacts very weakly with matter. This makes it difficult to detect and study. Additionally, the current data from experiments has not yet shown conclusive evidence for a fourth neutrino type, making it a subject of ongoing research and debate among scientists.

5. How would the discovery of a fourth neutrino type impact the scientific community?

If a fourth neutrino type is discovered, it would be a groundbreaking discovery in the field of particle physics. It would not only expand our understanding of the universe but also open up new avenues for research and potentially lead to new technologies. It would also require scientists to revise and update the Standard Model, which is the current framework for understanding the fundamental particles and forces of nature.

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