Distinguishing between R^2-inflation and Higgs-inflation
  We present three features which can be used to distinguish the R^2-inflation Higgs-inflation from with ongoing, upcoming and planned experiments, assuming no new physics (apart form sterile neutrinos) up to inflationary scale. (i) Slightly different tilt of the scalar perturbation spectrum n_s and ratio r of scalar-to-tensor perturbation amplitudes. (ii) Gravity waves produced within R^2-model by collapsing, merging and evaporating scalaron clumps formed in the post-inflationary Universe. (iii) Different ranges of the possible Standard Model Higgs boson masses, where the electroweak vacuum remains stable while the Universe evolves after inflation. Specifically, in the R^2-model Higgs boson can be as light as 116 GeV. These effects mainly rely on the lower reheating temperature in the R^2-inflation. 
Fedor Bezrukov, Dmitry Gorbunov
hep-ph astro-ph.CO