Following Philcox et al. [Phys. Rev. D 111, 103523 (2025)], we investigate a scenario with a massive partner to the inflaton ($\mathcal{O}(100)$ times the inflationary Hubble scale), in which particles are produced during a narrow time period, leaving characteristic hot or cold spots in the cosmic microwave background (CMB). Using tools developed for thermal Sunyaev-Zel’dovich cluster-finding, we search component-separated Planck PR4 $E$-mode maps for these hot spots, and compare to analogous results in $T$. Our analysis pipeline is validated on simulated observations and gives unbiased constraints for sufficiently large and bright hot spots. At Planck sensitivities, the temperature data are more sensitive to small hot spots, but for sufficiently large hot spots the polarization data are more sensitive. We improve upon earlier work by building a full Poissonian likelihood for the hot spot abundance. We find no strong evidence for primordial hot spots and thereby place novel bounds on the marginal and relevant couplings between the inflaton and massive scalars during inflation, probing physics at energies many orders of magnitude above any feasible terrestrial collider. The bounds derived from our new likelihood improve upon those of the above-mentioned paper by more than an order of magnitude for sufficiently light particles ($M_0\lesssim 100H_I$). We also forecast the inferred bounds on inflationary physics for a search using Atacama Cosmology Telescope (ACT) data, and from an optimistic cosmic-variance-limited experiment (CV), for which $E$-mode data provide stronger constraints than $T$ on nearly all scales. ACT should improve on the Planck constraints by $\gtrsim 10\%$, nearing the CV limit allowed by its sky coverage. Finally, we compare the constraining power of localized searches to that of a power spectrum analysis, and demonstrate that for sufficiently few produced particles the localized search performed herein is dominant.

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• Cosmic microwave background
• Inflation