Observational signatures of Higgs inflation

We investigate the dependency of Higgs inflation on the non-renormalisable matching between the low energy Standard Model limit and the inflationary regime at high energies. We show that for the top mass range m t ≳ 171.8 GeV the scenario robustly predicts the spectral index n s ≃ 0.97 and the tensor-to-scalar ratio r ≃ 0.003. The matching is however non-trivial, even the best-fit values m h = 125.09 GeV and m t = 173.21 GeV require a jump δλ ∼ 0.01 in the Higgs coupling below the inflationary scale. For m t ≲ 171.8 GeV, the matching may generate a feature in the inflationary potential. In this case the predicted values of n s and r vary but the model is still falsifiable. For example, a detection of negative running of spectral index at level α s ≲ −0.01 would rule out Higgs inflation.