Is natural inflation in agreement with CMB data?

Natural inflation is a well -motivated model for the early universe in which an inflaton potential of the pseudo-Nambu-Goldstone form, V (0) = Lambda 4[1 + cos (0/f)], can naturally drive a cosmic accelerated epoch. This paper investigates the observational viability of the minimally and non -minimally coupled natural inflation scenarios in light of current Cosmic Microwave Background (CMB) observations. We find that a small and negative coupling of the field with gravity can alleviate the well-known observational discrepancies of the minimally coupled model. We perform a Monte Carlo Markov Chain analysis of the Planck 2018 CMB and BICEP/Keck Array B-mo de polarization data to estimate how strong the coupling xi should be to achieve concordance with data. We also briefly discuss the impact of these results on the physical interpretation of the natural inflation scenario.