Art McDonald and Takaaki Kajita won the 2015 Nobel Prize in physics for discovering the oscillations between the 3 flavors of neutrinos; Electron, Muon, and Tau. This discovery showed that neutrinos have mass. It also explained why the underground neutrino detectors were only detecting $1/3$ of the predicted output of neutrinos from the sun. They were only looking for the 'Electron' flavor of neutrino.

In order for nuclear reaction involving the weak nuclear force to occur we need to conserve

  • mass/energy

  • charge

  • lepton number

Do we also need to conserve neutrino flavor?

  • The leptons that carry a $+1$ for lepton conservation purposes are:

    • electron($e^-$), muon ($\mu^-$), tau ($\tau^-$), electron neutrino($\nu_e$), muon neutrino($\nu_\mu$), tau neutrino($\nu_\tau$)
  • The leptons that carry a $-1$ correspondingly are:

    • positron($e^+$), anti-muon ($\mu^+$), anti-tau ($\tau^+$), electron anti-neutrino($\bar{\nu}_e$), muon anti-neutrino($\bar{\nu}_\mu$), tau anti-neutrino($\bar{\nu}_\tau$)

With the conservation rules cited, some significant antimatter creating situations are:

  • $p \rightarrow n + e^+ + \bar{\nu}_e$

  • $\bar{\nu}_e + p \rightarrow e^+ + n$

  • $\bar{\nu}_e + n \rightarrow e^+ +\bar{p}$

Please advise if there are errors in any of the above 3.

Of particular interest is the last one of the 3 because it yields both positrons and anti-protons when a Neutron absorbs an anti-neutrino.

What would be some situations that yield anti-neutrinos for use in the above situation?

While we know that neutrinos oscillate between the flavors of electron, muon, and tau; what are the ramifications when let's say a muon neutrino ends up striking the neutron? Can the oscillations go neutrino to anti-neutrino? This would not conserve lepton number but I still have to understand how conservation of momentum and mass are preserved as the neutrino oscillates flavors.

Update: In order to answer this question, scientists are building apparatus to investigate neutrino-less double beta decay of Xenon-136 atom nuclei. The theory is that neutrino-less double beta decay can only occur if the neutrino is its own anti-particle. This departure from the standard model was theorized by physicist Ettore Majorana.

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    $\begingroup$ Your third suggestion doesn't conserve baryon number. $\endgroup$ Commented Nov 28, 2017 at 3:08
  • $\begingroup$ @PeterShor According to my primitive understanding of baryon count: Neutron provides 1 for baryon count on left side and Anti-Proton provides baryon count of 1 on right side. I didn't know charge effects baryon count. $\endgroup$ Commented Nov 28, 2017 at 18:51
  • 3
    $\begingroup$ Charge doesn't affect baryon count. But being an antiparticle does. An anti-proton has baryon number −1, and a neutron has baryon number 1. See Wikipedia. $\endgroup$ Commented Nov 28, 2017 at 20:05


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