Cosmological Particle Production and Pairwise Hotspots on the CMB

TL;DR

This paper investigates how heavy particles produced during inflation can create localized hot or cold spots on the CMB, potentially revealing new physics beyond current observational sensitivities.

Contribution

It introduces a detailed analysis of pairwise hot spots caused by heavy scalar particles during inflation and assesses their detectability through CMB temperature profiles.

Findings

Heavy particles with masses around 100 times the Hubble scale can produce detectable hot spots.

The PHS signal can be distinguished using simple temperature cut searches.

The effects on CMB power spectra and bispectra are below current detection thresholds.

Abstract

Heavy particles with masses much bigger than the inflationary Hubble scale $H_*$, can get non-adiabatically pair produced during inflation through their couplings to the inflaton. If such couplings give rise to time-dependent masses for the heavy particles, then following their production, the heavy particles modify the curvature perturbation around their locations in a time-dependent and scale non-invariant manner. This results into a non-trivial spatial profile of the curvature perturbation that is preserved on superhorizon scales and eventually generates localized hot or cold spots on the CMB. We explore this phenomenon by studying the inflationary production of heavy scalars and derive the final temperature profile of the spots on the CMB by taking into account the subhorizon evolution, focusing in particular on the parameter space where pairwise hot spots (PHS) arise. When the heavy scalar has an $\mathcal{O}(1)$ coupling to the inflaton, we show that for an idealized situation where the dominant background to the PHS signal comes from the standard CMB fluctuations themselves, a simple position space search based on applying a temperature cut, can be sensitive to heavy particle masses $M_0/H_*\sim\mathcal{O}(100)$. The corresponding PHS signal also modifies the CMB power spectra and bispectra, although the corrections are below (outside) the sensitivity of current measurements (searches).