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How far ahead are we in Grand Unified Theory? Are we still searching for proton decay?
The Super-Kamiokande Experiment has used an independent method to exclude proton decay and related di-nucleon decays involving protons to charged leptons, neutrinos, photons and neutral and invisible to the experiment's detector's X particles, up to very large mean lifetimes on the order of 1031 to 1032 years.
So, over the life of the universe, the fraction of protons that decay as measured by these methods is less than one per 1021protons (in words, less than one hundred per gram of protons, and probably less than ten per gram of protons).
Previous studies using other methods have set a minimum proton lifetime on the order of 1033 to 1034 years, i.e. 1.0 to 0.1 such decays per gram of protons over the entire lifetime of the universe, or put another way, less than 1 such decay per 10 kilotons of protons per year (a measurement of truly stunningly great precision). A kiloton of protons is pretty much indistinguishable in mass from a kiloton of hydrogen at this level of precision in measurement.
The Grand Unified Theory is a theoretical framework in physics that aims to unify the three fundamental forces of nature - electromagnetism, strong nuclear force, and weak nuclear force - into a single, all-encompassing theory.
GUT attempts to extend the Standard Model by unifying the forces and particles described within it. It also seeks to explain the origin of particle masses and provide a deeper understanding of the fundamental nature of matter and energy.
Proton decay is a hypothetical process in which a proton, one of the building blocks of atoms, decays into lighter particles. It is important in GUT because some GUT models predict that protons can decay, providing a way to test and possibly validate these theories.
As of now, there is no experimental evidence for proton decay. However, various experiments, such as the Super-Kamiokande detector, have set limits on the proton decay rate, ruling out certain GUT models.
If proton decay is confirmed, it would have significant implications for our current understanding of the universe. It would provide evidence for the unification of forces and potentially explain the matter-antimatter asymmetry in the universe. It could also have implications for the stability of atoms and the long-term fate of the universe.