IAS-PHYS Fundamental Physics Seminar Series - Searching for Cosmological Collider Signals in the CMB Data

Abstract
Inflation provides a compelling framework for the generation of primordial fluctuations and offers a unique opportunity to probe particle physics at energy scales far beyond those accessible to terrestrial experiments. Recent developments in the cosmological collider program have highlighted the possibility of probing new particle species present during inflation. In these scenarios, the inflaton couples to additional massive fields whose exchange leaves distinctive imprints in primordial correlation functions. In particular, the bispectrum exhibits characteristic momentum dependence controlled by the particle mass and angular dependence determined by its spin. These signatures open the possibility of using the primordial Universe as a particle collider capable of probing energies inaccessible to laboratory experiments.
In this talk, the speaker will review recent developments in cosmological collider physics and describe how primordial bispectrum templates can be derived in a model-independent way using the boostless bootstrap. He will discuss the properties of these templates, in particular the distinction between the unique oscillatory part of the template and the single field EFT background. Next, he will summarize current observational efforts to detect cosmological collider signals, mostly in the cosmic microwave background (CMB). Particular emphasis will be placed on two complementary CMB bispectrum estimators employed in his analysis of Planck data. He will present current constraints on a range of cosmological collider scenarios and, time permitting, discuss the treatment of the look-elsewhere effect and future prospects for detecting cosmological collider signals.