[Triumf-seminars] TRIUMF Seminar today at 14:00

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Date/Time: Wed 2006-01-25 at 14:00

Location:  Auditorium          

Speaker:   Akram Mukhamedzhanov (Texas A & M)

Title:     Asymptotic normalization coefficients in nuclear reactions and nuclear astrophysics

Abstract: Asymptotic normalization coefficients (ANCs) are fundamental nuclear constants. They determine the amplitude of the tail of the projection of the bound state wave function of nucleus (a) onto the two-body channel (b+c). There is another model independent definition of the ANCs:  they determine the residue in the poles of the S matrix corresponding to a bound or resonance state. Thus for the resonant state the ANC is proportional to the width of the resonance.  In my talk I will address application of the ANC in nuclear reactions and nuclear astrophysics.  In particularly, I will present definitions of the ANC, different reactions which can be used to determine the ANC. I will show the Coulomb renormalization of the ANC and discuss how mirror symmetry can be used to determine the ANCs for radioactive nuclei using stable beams.

     After that I will address the application of the ANC method for determination of the astrophysical factors for different key reactions of the CNO and Ne-Na cycles. Important part of my talk is application of the ANC method for astrophysical processes proceeding through the subthreshold states. In particular, I will present the results for the slowest reaction of the CNO cycle ^14N(p,gamma)^15), which controls the energy production in the CNO cycle. The reaction rates for this reaction provide limitation on a lower bound of the age of the universe.

      I will demonstrate how to use the ANC method to determine the interference sign of direct and resonant capture amplitudes, and, hence, the astrophysical factor at astrophysically relevant energies for another important astrophysical reaction ^13N(p,gamma)^16O. I will address also the very recent results for the astrophysical factors for ^13N(alpha,n)^16O and ^20Ne(p,gamma)^21Na. The first reaction is a neutron generator for s processes and it proceeds through the subthreshold state ^17O(s^{+}_{1/2}, 6.356 MeV). The ANC for this state has just been determined by G. Rogachev et al. (Florida State University) using the subCoulomb transfer reaction ^13C(^6Li,d)^17O performed in the inverse kinematics.  The second reaction, ^20Ne(p,gamma)^21Na, is the first reaction of the Ne-Na cycle. Its proceeds through the ^21Na(s^{+}_{1/2}, 2.425 MeV). Its ANC has been determined using the ^20Ne(^3He,d)^21Na transfer reaction.


Please note the unusual day. Stimulants will be available 15 minutes before the talk.

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