Is the proton lifetime to $e+ \pi0$ below $10^{35}\,\mathrm{years}$?
In plain words
Grand unified theories predict a proton can decay into a positron and a neutral pion. Huge water detectors watch for this rare event.
Precise statement
Measure or bound $\tau(p \to e+ \pi0)/B$, currently $> 2.4 \times 10^{34}\,\mathrm{yr}$ (Super-Kamiokande, 2020, 90 percent CL). Non-supersymmetric $\mathrm{SO}(10)$ models with intermediate scales typically predict $10^{34}\text{ to }10^{36}\,\mathrm{yr}$. An answer is a detection or a limit near $10^{35}\,\mathrm{yr}$.
What would settle it
Hyper-Kamiokande exposure of about 1 to 2 Mt-yr reaching $\sim 10^{35}\,\mathrm{yr}$ sensitivity.
Status in the literature
Hyper-Kamiokande construction is under way, with data expected late in the 2020s.
Parent problems
- Special case of Do the SM gauge forces unify into a single group? · open · from revision 1 The parent was revised since revision 1: it now states another question.
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