[Triumf-seminars] TRIUMF Theory Seminar today at 13:00

TRIUMF Seminars triumf-seminars at lists.triumf.ca
Tue May 5 05:00:02 PDT 2015


Date/Time: Tue 2015-05-05 at 13:00

Location:  Auditorium          

Speaker:   Xilin Zhang (University of Washington)

Title:     How well do we know about 7Be+p->8B+photon? an Bayesian analysis based on effective field theory

Abstract: The radiative proton capture reaction, 7Be+p->8B+photon, is a subject of long-standing interest for nuclear astrophysics. It needs to be known at very low (around 20 keV) energies, which is too small to be measured directly because of the Coulomb barrier. 
In this talk I will present our studies of this reaction in the so-called Halo-Effective-Field-Theory (Halo-EFT) framework, which provides a systematic expansion for the reaction amplitude. The 8B nucleus is considered as a shallow proton+7Be core (and 7Be excited state) p-wave bound state. In our leading order (LO) calculation, the relevant four EFT couplings were fixed against the 8B bound state properties from ab initio quantum-Monte-Carlo calculations and measurements, and the measured proton+7Be s-wave scattering lengths. The LO results compare favorably with available direct capture data within the estimated theoretical uncertainty. In the next-to-leading order (NLO) calculation, another five EFT parameters need to be calibrated. With the LO+NLO analytical cross section formula in hand, we use Bayesian analysis to infer the EFT parameters from the direct capture data and measured s-wave scattering lengths, and then extend it to study the S factor at low energies. As a result, we get an interesting constraint on the sum of 8B wave function asymptotic normalization coefficient squares, and a stringent constraint on zero energy S factor, S(0)=21.03 (eV b)+0.81-0.86 (eV b). The latter constraint compares with 0.7 eV b error from the capture data and 1.4 eV b theoretical error in a recent evaluation of S(0). In the end of the talk, I will discuss how the improvements of direct capture and s-wave scattering measurements impact the constraint on S(0).



______________________________

General TRIUMF seminar information available at http://www.triumf.ca/home/upcoming-events/about-seminars-lectures



More information about the Triumf-seminars mailing list