this post was submitted on 09 Jun 2024
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You’re not alone; matter-antimatter asymmetry is one of the big open questions in physics. Most particle processes treat matter and antimatter identically, but there are a few areas where matter and antimatter have slightly different interactions. These occurrences are violations of Charge Parity symmetry aka CP Violation.
There must have been a certain amount of CP violation during the early phases of the Big Bang to explain our matter-dominated universe. But the known amounts of CP Violation are nowhere near enough to explain the asymmetry in matter and antimatter. There are some proposed mechanisms that would violate CP symmetry in sufficient quantities, but these haven’t been experimentally observed. There are ongoing searches to detect these processes, or related processes that would be possible if these existed. Neutrinoless double beta decay searches are one example of these detection efforts.
In summary, there’s a guaranteed Nobel Prize to whoever can answer your question.
I never thought I'd read the words "CP violation" and actually be interested and intrigued instead of disgusted.
Yeah it’s one of those terms that’s unfortunately been co-opted for another definition. Definitely made some of my google searches in grad school feel icky… The physics terminology came first though!
I work on a 0nuBB search doing detector R&D, this is spot on, but has 2 extra components. The three elements needed for explaining the asymmetry are:
These are the Sakharov conditions for Baryogenesis/Leptogenesis. #1 has been observed via the weak interaction but not in large enough quantities and is not observed via strong interactions, #2 is what proton decay and 0nuBB searches look for, and #3 can be, at least partially, explained by the expansion of the universe as a non-equilibrium interaction.
To get from leptogenesis to baryogenesis requires theretical physics I only barely understand using particles call sphaelerons that convert leptons to baryons.
I heard the subway guy got in trouble for a CP Violation
Are there other theoretical interactions or consequences of interest if neutrinos turn out to be their own antiparticle? That idea is blowing my mind.
There absolutely are, but I’m not super familiar with all of the consequences of majorana neutrinos. /u/[email protected] might be able to provide a better answer. My background is experimental nuclear physics, so I’m familiar a lot of experiments searching for beyond the standard model physics, but less so with the theory motivation.
One consequence of neutrinos being their own antiparticles is that it breaks lepton number conservation. This also breaks chiral symmetry, since all neutrinos are right-handed and anti-neutrinos are left-handed. This observation would also imply that neutrinos have mass - which is assumed but would be a really big deal to prove.