A search for super-imposed oscillations to the primordial power spectrum in Planck and SPT-3G 2018 data

Abstract

We search for super-imposed oscillations linearly or logarithmically spaced in Fourier wavenumbers $k$ in Planck and South Pole Telescope (SPT-3G) 2018 temperature and polarization data. The SPT-3G temperature and polarization data provide a new window to test these oscillations at high multipoles beyond the Planck angular resolution and sensitivity. We consider linear and logarithmic oscillations with a constant amplitude, or with a power-law dependence or a Gaussian modulation, always in $k$. These models correspond to three, four and five additional parameters beyond power-law primordial power spectrum for the templates considered, respectively. We find that each of the five models considered can provide an improved fit to Planck data, consistently with previous findings, and to SPT-3G data, always compared to power-law power spectrum. We find tighter constraints on the amplitude of the super-imposed oscillations from the combined Planck/SPT-3G data set than in each individual data sets. For linear oscillations, with the amplitude allowed to vary as a power-law in $k$, as in the case of EFT, we find that the addition of SPT-3G data sets tighter constraints on the possibility that the amplitude increase at small scales. When the ranges of parameters which provide a better fit to Planck and SPT-3G data overlap, as in the case of Gaussian modulated oscillations, we find a larger $Δχ^2 \sim - 17.5 \, (-14.7)$ for logarithmic (linear) oscillations - in a combined Planck/SPT-3G data set than in each individual data sets. These findings will be further tested with upcoming CMB temperature and polarization measurements at high multipoles provided by ongoing ground experiments.