Final answer:
Proton decay is significant in testing GUTs indirectly. Although no decay has been detected, extending proton lifetime constraints, it doesn't disprove GUTs but adds constraints for theoretical refinement.
Correct option is; c) It provides indirect evidence for GUTs
Step-by-step explanation:
In the search for Grand Unified Theories (GUTs), proton decay plays a critical role. It offers an indirect means of testing these theories, which aim to merge the electromagnetic, weak, and strong nuclear forces into a single force.
According to current GUT models, the decay of protons should occur, even if over an immensely long timescale (about 1031 years). Such decay would violate the conservation of baryon number and electron family number.
Advanced experiments, such as those conducted at the Super-Kamiokande in Japan, search for evidence of this decay to validate GUT predictions.
However, the absence of observed proton decay so far has not confirmed many GUTs; instead, it has extended the experimental lifetime of protons beyond current expectations to greater than 5 × 1032 years, thereby placing additional constraints on these theories but not disproving them outright.
This illustrates the iterative nature of scientific theories and the complex challenges in the field of particle physics.