First Search for Kaluza-Klein Gravitons and Radion Using Planck Data
Alexander P. Cassem, Soubhik Kumar
astro-ph.CO, hep-ph, hep-th
Submitted: 2026-07-02
Comments: 20 pages, 12 figures
License: http://creativecommons.org/licenses/by/4.0/
The gist: Heavy moduli and Kaluza-Klein (KK) gravitons from extra dimensions may evade terrestrial probes but can be produced during inflation, generating primordial non-Gaussianity (NG) through unavoidable
Terminology
Abstract
Heavy moduli and Kaluza-Klein (KK) gravitons from extra dimensions may evade terrestrial probes but can be produced during inflation, generating primordial non-Gaussianity (NG) through unavoidable couplings to density perturbations. In a warped five-dimensional (5D) model, we compute the full radion- and KK-graviton-mediated bispectra and perform the first search for these signals using Planck 2018 temperature and polarization data. We find no significant evidence for NG, with the maximum significance being 1.8 sigma for m KK about 1.6H. We also identify a 5D setup which naturally generates NG with f NL about 1-50, within the reach of future surveys.
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