Baryon asymmetry of the universe

[Kajagoogooooooo]

I don't understand why CP violation is insufficient to explain the observed baryon asymmetry?
in every article I find it says: "we know its insufficient..." without an explanation.
I will be glad for an explanation and for articles that deal with this issue.
And how do you solve it using the lepton sector?
Again articles that are talking about this issue will be great in addition to an explanation :)

 

[mfb]

As usual, Wikipedia gives an overview that is easy to find.

CP violation alone doesn't give you a process that would change the baryon number.
CP violation and baryon number in thermal equilibrium would change the baryon number only randomly, i.e. it would stay extremely close to zero.

You need all three - CP violation to make a difference between baryons and antibaryons, a process that can change the baryon number, and conditions that favor one direction over the other, to get a baryon asymmetry.

 

[PeterDonis]

I don't understand why CP violation is insufficient to explain the observed baryon asymmetry?

As a simpler way of saying what @mfb said: all of the CP violating processes in the Standard Model are weak interactions, and the weak interaction conserves baryon number.

 

[Kajagoogooooooo]

As I have read you need to satisfy Sakharov conditions in order to make matter-antimatter asymmetry:
https://physics.stackexchange.com/questions/24042/baryon-asymmetry
1. CP violation has been approved in the Cronin and Fitch experiment.
2. Interactions out of thermal equilibrium - Our universe in out of thermal equilibrium due to the growth in entropy so it satisfies this too.
3. I understand that the problem lies in: Baryon B violation
I just don`t understand what it means Baryon B violation, and why it is not happening?
Because if 3. happens too, there is no problem to explain the matter-antimatter asymmetry.

 

[PeterDonis]

I just don`t understand what it means Baryon B violation, and why it is not happening?

"Baryon B violation" just means interactions that do not conserve baryon number. All of the Standard Model interactions do conserve baryon number, and those are the only interactions we know of (other than gravity, which obviously conserves baryon number). That's why the question of where matter-antimatter asymmetry comes from is a question.

 

[Buzz Bloom]

That's why the question of where matter-antimatter asymmetry comes from is a question.

Hi Peter:

I wonder if the question about the origin of asymmetry have some hypotheses that attract a majority of professionals to think they are more likely to be correct than others. For example, during the earliest era when particles are created randomly, might a statistical excess of matter particles rather than antimatter particles exist, and when that period ends, the excess would survive during the annihilation of pairs. Might it be possible to estimate the number of paired particles that annihilate each other compared with the number of surviving matter particles? Might this ratio have some surviving characteristic that could me measured today?

Regards,
Buzz

 

[PeterDonis]

might a statistical excess of matter particles rather than antimatter particles exist, and when that period ends, the excess would survive during the annihilation of pairs

There's no "might" about it; this is what we believe happened. The question is, where does the "statistical excess" come from? There would have to be some process that can affect baryons and anti-baryons differently (or quarks and anti-quarks), and we know of no such process. In the absence of such a process, there is no way to ever have a different number of baryons and anti-baryons; they have to balance.

Might it be possible to estimate the number of paired particles that annihilate each other compared with the number of surviving matter particles?

Again, there is no "might" about it; we have estimated this. The key parameter is the ratio of photons to baryons in the universe, which is estimated to be about a billion photons per baryon; this means, heuristically, that the excess of baryons over anti-baryons before annihilation was about one in a billion.

https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis#Baryon–photon_ratio

 

[Kajagoogooooooo]

There's no "might" about it; this is what we believe happened. The question is, where does the "statistical excess" come from? There would have to be some process that can affect baryons and anti-baryons differently (or quarks and anti-quarks), and we know of no such process. In the absence of such a process, there is no way to ever have a different number of baryons and anti-baryons; they have to balance.
Again, there is no "might" about it; we have estimated this. The key parameter is the ratio of photons to baryons in the universe, which is estimated to be about a billion photons per baryon; this means, heuristically, that the excess of baryons over anti-baryons before annihilation was about one in a billion.

https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis#Baryon–photon_ratio

I heard about some who believe the answer lies in the lepton sector or in the neutrino sector, can you expand on this issue?

 

[PeterDonis]

I heard about some

Can you give a reference?

 

[Kajagoogooooooo]

Can you give a reference?

from an article written by yanagida and peccei.
I can put a link if you wish.

 

[George Jones]

View attachment 223751
from an article written by yanagida and peccei.
I can put a link if you wish.

When asked for a reference, as a minimum, you also should give the title of the article, and the name of the journal, article, text, or proceedings. A link would be nice.

 

[Kajagoogooooooo]

When asked for a reference, as a minimum, you should give the title of the article, and the name of the journal, article, text, or proceedings. A link would be nice.

Leptogenesis as the Origin of Matter
Buchmuller Peccei and Yanagida

 

[George Jones]

When asked for a reference, as a minimum, you also should give the title of the article, and the name of the journal, article, text, or proceedings. A link would be nice.

Leptogenesis as the Origin of Matter
Buchmuller Peccei and Yanagida

You didn't meet my minimum.

 

[George Jones]

For articles on the arXiv, perhaps the best method of reference is a link, e.g.,

https://arxiv.org/abs/hep-ph/0502169

The linked page contains a lot of information: article title; article authors; journal reference; abstract; link to pdf version of the full article.

This would have required less effort than your original response to the request for a reference.

It may seem like nitpicking, but communication is important. I have a friend who worked for a large, well-known multinational company for more than 25 years. This company, call it A, has other large, well-known multinational companies as clients. Employees at A were not allowed to be in positions that interacted with important clients if the communications skills of said employees were below a suitable level.

 

[PeterDonis]

I can put a link if you wish.

If you read the PF rules on references, you will know that we do wish. Telling people to Google is not acceptable. Posting a PDF is not acceptable (partly because of copyright issues; we have no way of verifying that you have the right to post it).

It may seem like nitpicking

It's not. The reasons you give for linking are perfectly valid. Other reasons include the one I mentioned above.

 

[mfb]

All of the Standard Model interactions do conserve baryon number, and those are the only interactions we know of (other than gravity, which obviously conserves baryon number).

The SM conserves baryon numbers only at low energies. At high energies sphalerons can convert baryons to antileptons and vice versa.
Gravity does not care about baryon number, and therefore does not conserve it. You can feed a small black hole with baryons only and get an equal amount of baryons and antibaryons out (if it is small enough for Hawking radiation of baryons).

Because if 3. happens too, there is no problem to explain the matter-antimatter asymmetry.

It is not sufficient to find a mechanism - you also have to get the numbers right. In particular, the CP violation we found so far is way too small to explain the observed baryon to photon ratio.

I heard about some who believe the answer lies in the lepton sector or in the neutrino sector, can you expand on this issue?

This is related to the sphaleron process I mentioned before. An asymmetry in the lepton sector can lead to an asymmetry in the baryon sector. But where does the asymmetry in the lepton sector come from? Large CP violation with neutrinos has not been ruled out, and in general neutrino mixing is very interesting.