# Testability of GUTs at the LHC

## Main Question or Discussion Point

Hello,

my understanding of particle physics is very limited. I know that several GUTs involving various symmetries have been proposed. My question is, wether experiments at the LHC can help to rule out or even verify some of the proposed GUTs? Maybe someone has some specific answers. Thank you!

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Haelfix
Doubtful, the usual hypothetical GUT scale is at very high energies, near the Planck scale, many orders of magnitude away from what the LHC probes. The best you can do is get better experimental precision on the standard coupling constants (Electroweak, Strong) that way we can refine the interpolation when we run them down to that scale to see if they unify. Right now, they nearly hit but not quite (with Supersymmetry its even closer).

Barring that, we need better precision on the bounds of potential proton decay (a typical prediction of GuTs is that indeed protons do decay after a very long time) but the LHC won't help us there directly either.

Still sometimes there are roundabout ways of getting there, depending on which physics we see or don't see but I wouldn't count on it.

I respectfully disagree with the post above. Many GUTs include decompositions such as (and as a very simple example):

$$SO(10) \to SU(5) \otimes U(1)_{GUT} \to SU(3) \otimes SU(2) \otimes U(1)_{Y} \otimes U(1)_{GUT}$$

The new U(1) would exhibit itself as a new neutral current process (so called Z primes). There are further decompositions where one finds new SU(2) x U(1), implying W primes as well as Z primes.

There are people actively looking for these things in various channels of potential interest, and some models provide striking signatures. Now, we will either make some exceedingly exciting discoveries or rule out certain models and model parameters.

Haelfix