What is proton decay and will matter disappear?

Proton decay is a hypothetical particle physics process where a proton breaks down into lighter non-quark particles, testing the fundamental stability of matter and baryon number conservation. While the Standard Model treats the proton as stable, Grand Unified Theories predict that protons can decay with half-lives ranging from 10 to the 31st to 10 to the 36th years. Despite extensive experimental monitoring in facilities like Super-Kamiokande, proton decay has never been observed.

What we know

Proton decay is the hypothetical decay process of a nucleon into non-nucleons. [1]
In the Standard Model, the proton is considered stable because baryon number conservation prevents it from decaying on its own. [2]
Grand Unified Theories predict that protons can decay via the Higgs particle, magnetic monopoles, or new X bosons with a half-life between 10^31 and 10^36 years. [2]
Despite significant experimental efforts, including monitoring vast amounts of water in facilities like Super-Kamiokande, proton decay has never been observed. [2]

Still open

The exact proton lifetime remains unknown, with theoretical models predicting half-lives ranging anywhere from 10^31 to 10^36 years.

Where to go next

Sources

[1]proton decay (Wikidata Q1065997) · CC0 1.0
[2]Proton decay · CC BY-SA 4.0
[3]Proton emission · CC BY-SA 4.0
[4]Proton · CC BY-SA 4.0
[5]Positron emission · CC BY-SA 4.0