Understand
The recently discovered 125 GeV boson appears very similar to a Standard Model Higgs, but with data favoring an enhanced h to gamma gamma rate.
- A number of groups have found that fits would allow (or, less so after the latest updates, prefer) that the h-t-tbar coupling have the opposite sign.
- This can be given meaning in the context of an electroweak chiral Lagrangian, but it might also be interpreted to mean that a new colored and charged particle runs in loops and produces the opposite-sign hGG amplitude to that generated by integrating out the top, as well as a contribution reinforcing the W-loop contribution to hFF.
- In order to not suppress the rate of h to WW and h to ZZ, which appear to be approximately Standard Model-like, one would need the loop to "overshoot," not only canceling the top contribution but producing an opposite-sign hGG vertex of about the same magnitude as that in the SM.