[l33tman]

The paper describing the theoretical steps necessary to compute g for the muon is hundreds of pages of condensed math, theorems and approximations etc.

The SM Lagrangian is not computable, so a big part of theoretical physics is about finding tricks to actually compute it.

Incidentally this is why there is disagreement on the muon g-2 discrepancy, at least two theory groups have calculated different values using different approximations.

[sigmoid10]

It should be noted that the anomalous electron g-2 is computable analytically (at least to very good approximation) which makes the theoretical value much less controversial. The anomalous muon g-2 however depends more heavily on interactions of quantum chromodynamics, which can only be computed using numerical lattice QCD simulations. This is notoriously hard and has only become practical in recent years, hence why theorists don't yet fully agree on the value.

Also, computing even just one part of this value is basically on the level of a theoretical particle physics dissertation. Don't expect to be able to do this without several years of research experience in this specific field.