3:30–5:00 pm ERC 161
Title: New He4 observations and their impact on Big Bang Nucleosynthesis and Physics Beyond the Standard Model
Abstract: Big bang nucleosynthesis provides a window to the physics of the universe just seconds after the big bang. Its predictions of the light element abundances of D, He4, and Li7 can be compared with observational determinations. To do so, we make use of measurements of the microwave background which provide precise values for the baryon density of the universe, a key input used in abundance predictions. The abundance of D is measured to a accuracy of ~1%, far more precise than theoretical calculations. In contrast, the He4 abundance is predicted with an accuracy of better than 0.1%. The LBT Yp Project's new measurement of the primordial He4 mass fraction is the most precise measurement to date with an observational uncertainty of 1/2%. By combining the new helium abundane with the latest primordial deuterium measurements, I will assess the consequences for standard BBN with three neutrino flavors. When N_nu is allowed to vary, the new He4 measurement sets strong constraints on the physics beyond the Standard model, with N_nu-3 < 0.125.
Zoom: https://uchicago.zoom.us/j/95272936732?pwd=HXVM29KzFU5yU8WvLcXKsxa9HlSTLE.1
