Investigating cosmic origin and evolution with CMB-S4

The red-hot glow of the primordial universe, after 13.8 billion years of redshift, is observed today by our telescopes as the Cosmic Microwave Background (CMB). Spatial variations of CMB intensity and polarization across the sky provide a record of conditions in the early universe, possibly encoding signatures from cosmic inflation and traces of undiscovered relic particles. Additionally, the CMB ‘backlights’ the universe’s large-scale structure and picks up the influence of all matter, including neutrinos, on its way to us. Ground-based CMB imaging instrumentation has made generational leaps in sensitivity over the past few decades, while our understanding and mitigation of systematic errors in CMB measurements has advanced. CMB-S4 is the largest conceived ground-based CMB experiment that will map over 40% of the Southern sky from Chile and Antarctica in the 2030s. It will conduct the most sensitive search yet for inflation, complement DESI and LSST in aiding our understanding of cosmic acceleration, and enhance studies of neutrinos and dark matter from other experimental efforts. CMB-S4 has garnered broad support from the physics and astronomy communities as indicated by endorsements from the Astro2020 Decadal Survey, and most recently as the top-ranked DOE HEP project in the 2023 P5 report. I will discuss the motivation and design for the CMB-S4 experiment, highlighting current R&D effort at SLAC and KIPAC. In particular, ongoing research and findings from contemporary experiments such as BICEP, South Pole Telescope and Simons Observatory play a critical role in informing prototypes and optimizing design and methods for CMB-S4 to achieve its ambitious science goals.

Speaker: Zeeshan Ahmed, SLAC National Accelerator Laboratory

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