Smoking Guns for On-Shell New Physics at the LHC

Abstract

Using Tevatron bounds we derive upper limits on the LHC Higgs production rate under the assumption that no beyond the Standard Model (BSM) particles are being produced near their mass shell. A violation of these limits would constitute a smoking gun for light BSM particles. Furthermore, we demonstrate how R_T, the ratio of the partially integrated Higgs transverse momentum distribution to the inclusive rate, can also be used as a probe of light BSM particles. This ratio is insensitive to heavy virtual effects and can be well-approximated by its SM value, i.e. it is model independent. The perturbative expansion for R_T has reduced renormalization scale dependence, at the order of 5% at next-to-leading order in QCD, due to a cancellation of Wilson coefficients. A deviation from the SM value implies that light BSM particles are being produced near their mass shell. We discuss a possible loophole to this conclusion, namely the existence of a non-perturbative, CP violating sector that couples to the Higgs. We use a toy model with colored scalars to demonstrate how the model independent prediction for R_T is approached as the mass of the scalar becomes large.