Do Neutrinos Need to be Their Own Antiparticle for Majorana Masses to Exist?

In summary, the conversation discusses the possibility of the seesaw mechanism as a potential explanation for neutrino masses. It is noted that Majorana mass terms violate lepton number conservation and can only exist for neutral particles like neutrinos. However, it is still unclear if neutrinos are their own antiparticles and thus have Majorana masses. The conversation also mentions that Majorana masses could still explain neutrino masses, but at a small scale that is difficult to measure currently. The best search for Majorana masses is through neutrinoless double beta decay searches, but the current experimental constraints are still limited.
  • #1
Trixie Mattel
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So we are not yet sure exactly what mechanism accounts for the neutrino masses. One possible mechanism is the seesaw mechanism.

Am I correct in thinking:

Majorana mass terms are born from couplings between particles and antiparticles. This violates lepton number conservation and charge conservation. Therefore only neutral particles can have Majorana mass terms, i.e neutrinos. However that still does not account for lepton number. Is it therefore a requirement that neutrinos be there own antiparticle (i.e Majorana particles) for Majorana terms to exist so as to conserve lepton number?
 
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  • #2
Lepton number is not conserved if neutrinos are Majorana particles.
 
  • #3
Orodruin said:
Lepton number is not conserved if neutrinos are Majorana particles.
So, if Majorana mass terms violate lepton number conservation, why is it thought that it can be a method to explain the mass of a neutrino?
 
  • #4
The logic is the other way round.

Majorana masses are possible - consistent with observations so far and without theoretical issues.
Majorana masses would lead to lepton number violation, but too small to be found by current measurements. Future measurements are more sensitive, they might find it.

The best searches for Majorana masses are neutrinoless double beta decay searches. From neutrino oscillations, the most likely masses are <5 meV, 7-10 meV and 50 meV, although slightly higher masses have not been ruled out and there is still the option of an inverted order where one neutrino is light and two are relatively heavy (50-80 meV). Here is a recent review, figure 6 summarized the current experimental constraints from mixture measurements. Figure 17 shows the current upper limits of neutrinoless double beta decay searches. Figure 21 does some combinations.
 
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  • #5
mfb said:
The logic is the other way round.

Majorana masses are possible - consistent with observations so far and without theoretical issues.
Majorana masses would lead to lepton number conservation, but too small to be found by current measurements. Future measurements are more sensitive, they might find it.
thank you! But I thought the Majorana masses didn't conserve lepton number? As it allows coupling of particle and antiparticle pairs??
 
  • #6
Oops, I meant violation of course. Fixed.
 
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  • #7
mfb said:
Oops, I meant violation of course. Fixed.

Oh right, perfect. Thank you very much!
 

1. What are neutrinos and how are they related to Majorana mass?

Neutrinos are subatomic particles that have no electric charge and interact only weakly with other particles. Majorana mass refers to a theoretical property of neutrinos that would allow them to be their own antiparticles.

2. How do we detect neutrinos and study their mass?

Neutrinos are detected using specialized detectors that can identify the tiny signals produced when a neutrino interacts with matter. The study of neutrino mass involves experiments that measure the properties of neutrinos, such as their energy and momentum, and infer their mass based on theoretical models.

3. What is the significance of Majorana mass in particle physics?

The existence of Majorana mass in neutrinos would have important implications for our understanding of the fundamental particles and forces in the universe. It would also provide insight into the nature of dark matter, as neutrinos are a potential candidate for this elusive substance.

4. Are there any confirmed observations of Majorana neutrinos?

While there have been several experiments that have observed possible signs of Majorana mass in neutrinos, there is currently no definitive evidence for its existence. The search for Majorana neutrinos is ongoing and will require more precise experiments and data analysis.

5. How does the discovery of Majorana neutrinos impact our understanding of the Standard Model of particle physics?

If Majorana mass is confirmed in neutrinos, it would require modifications to the Standard Model, which is the current theoretical framework for understanding the fundamental particles and forces in the universe. It would also open up new avenues for research and potentially lead to a more complete understanding of the universe.

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