Wednesday, February 9, 2022 from 04:00 PM to 05:00 PM 

Where By Zoom (details below) 

Contact Name Michael Lubell 

Contact Phone 212-650-5610 mlubell@ccny.cuny.edu

Physics Colloquium 

Stellar Evolution in the Light of Gamma Beams

Moshe Gai

Professor

Department of Physics

University of Connecticut, Storrs, CT

Abstract 

Stellar evolution theory is a mature science that led to the standard solar model. It allows us to use the sun as the best well understood neutrino source with an accuracy of 1%. But in this theory the Carbon-Oxygen (C/O) ratio at the end of helium burning remains elusive. It was dubbed by Willie Fowler in his 1984 Nobel speech as a problem of "paramount importance", and it remains so today. For example, Type II supernova progenitor stars with C/O < 1, leaves behind a black hole and for C/O > 1, a neutron star. The C/O ratio also plays an important role in the light curve of Type Ia supernova that are used today as cosmological candles leading to the discovery of “Dark Energy”.

We developed a new method to approach this problem [1] using a gamma-beam from the Duke FEL light source and a time projection chamber (TPC) detector, also serving as the target. We measure new data with quality that surpass efforts of the last four decades. For example, we resolve a nagging disagreement of measured data with unitarity.

I will present for the non-expert, an introduction to stellar evolution theory [2,3], define the​ problem, and review our new method. Light source gamma-beam facilities in the USA (Duke) and constructed in the EU (ELI-NP in Romania), allow us to anticipate a solution to this four-decade problem of stellar evolution theory.

[1] Robin Smith, Moshe Gai, Sarah R. Stern, Deran K. Schweitzer, Mohammad W. Ahmed, Nature Communications 12, 5920 (2021), https://www.nature.com/articles/s41467-021-26179-x

[2] Moshe Gai and Robin Smith, The Innovation Platform, 8, 208 (2021), https://www.innovationnewsnetwork.com/shining-light-nuclear-astrophysics/15139/

[3] Hans A. Bethe and Gerald Brown, Scientific American, 252,#5, 60 (1985)

Biography

Moshe Gai is a Professor of Physics at the University of Connecticut and Director of the Laboratory for Nuclear Science at Avery Point, aka the Astrophysics Laboratory. He graduated Magna cum Laude from the Hebrew University of Jerusalem, and received his Ph.D. from Stony Brook University in 1980. At Yale University, he was a post doc of D. Allan-Bromley from 1980 to 1984, an Assistant Professor and Associate Professor of Physics from 1984 to 1994, and an adjunct Professor from 1995 to 2015. He joined the faculty of the University of Connecticut in 1994. Previously he served as a Lieutenant of the Israeli Commando (Sayeret). He was severely wounded but after two years, partially recovered from paralyses. He specializes in experimental nuclear astrophysics and nuclear structure and has been a fellow of the American Physical Society since 1998. His 1989 work provided the strongest refutation of “cold fusion.” It was reviewed in Time Magazine and in numerous books, and its conclusions were reported to the White House by D. Allan Bromley, President George H.W. Bush’s science adviser. Professor Gai is a fellow of the American Physical Society, and he has received a number of awards, including the 2016 Best Research award at the University of Connecticut, Best Lecturer award of the 2016 Carpathian Summer School, the 2013 most valued referee of the Nuclear Physics journal publication. He was named an Invited Eminent Professor of RIKEN, by Japan in 1995.