Proton Decay Modes

Question

May I know the proton decay mode predicted by Theoretical Physics?

These are the decay mode I've found:

1: $p^+\rightarrow e^++\pi^0$

2: $p^+\rightarrow \mu^++\pi^0$

Answer 1

Possible decay channels could be \begin{eqnarray} p & \rightarrow & e^{+} + \eta \\ p & \rightarrow & \mu^{+} + K^{0} \\ p & \rightarrow & \bar{\nu_{e}} + \pi^{+} \\ \end{eqnarray} There could be many more. Thing we should remember is none of these processes ever observed. Proton decay is one of the prediction of grand unified theories. Where quarks are leptons placed in a same multiplet like [16] in $SO(10)$ or [5] in $SU(5)$. There are gauge bosons, which carries both $SU(2)_{L}$ weak isospin and $SU(3)_{C}$ color charges. Which can transform quarks into leptons consequently can trigger the proton decay. Mass of these gauge bosons in $SU(5)$ GUT is around $10^{15}GeV$ (remember the Planck energy $10^{19}GeV$). Till date no signature of these gauge bosons observed. Besides proton is highly stable, it has life time longer than the age of the universe! That is why GUT model like $SU(5), SO(10)$ has been ruled out by experiment. Nevertheless their supersymmetric extensions are still in the market, crying to be tested in the lab.

Answer 2

None of them are predicted by theoretical physics(standard model), however it is a major component of beyond the standard model physics. This is used to explain why there is any matter in the universe and why antimatter did not annihilate all the matter. It goes along the lines that proton decay happened once to the antiprotons and that this might happen to the regular protons. Of course the reaction is going to be opposite to regular proton decay because of charge but it is going to be similar. It proves that antiprotons are more unstable than protons. However if this was the case even if protons did not decay, any antiprotons would have decayed in the LHC.(probably long before the annihilation with regular old protons.)

There are a lot of correct ways in which protons could decay. Though there is a really popular one. This is where the two up quarks in the proton fuse to give us a boson called the X boson which decays into the anti-down quark and a positron. The positron is ejected and the antidown quark and the down quark that remained merge to create the pion. So the end products are one pion, and a positron. The pion decays into photons after a certain period of time.

Of course all of this is beyond the standard model physics and there is no proof of these things as far as experiments(maybe even as far as theories) are concerned.