[btilly]

Every one of those parameters is associated with a field that does symmetry breaking. Every one of those fields has a particle associated. Every one of those particles has been observed, studied, and found to have properties in line with what would be required for the fields to have the values that we measure.

So yes, that's a lot of free parameters. But they are intrinsic to the theory. And we have considerable experimental evidence that they represent something real.

For those who don't know what symmetry breaking is, the Standard Model has a lot more symmetries than the observed universe. For example the theory does not specify that electromagnetism is long range while the strong nuclear force is short range. Or that the muon weighs more than the electron. But for each symmetry in the theory that we don't see in practice, there is a field that specifies the value of the observed asymmetry. Each field is carried by a particle. Each particle has properties that reflect the value of all of the fields. Every particle has been found and almost all have the predicted properties (to within measurement error).

The last particle found was the Higgs boson. The Higgs field determines the relative masses of different particles.

The "almost all" is the fact that the neutrino has 3 versions and oscillates between them in flight. Also the neutrino is not massless. While the Standard Theory can adapt to match this, this isn't what was originally predicted.

[kelseyfrog]

Right, and some physicists have a nagging feeling that the addition of another symmetry would result in the reduction in free parameters. "We've done it before, so why shouldn't it work again?" is their thought process. So they devise a model which replicates the standard model in observable ranges and to make it testable, doesn't replicate the standard model outside of the observable range. This is an attempt to make the model falsifiable and thus scientific. Then they advocate for expensive accelerators to falsify the model.