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

[postmaster at admin.triumf.ca]

Date/Time: Mon 2009-12-07 at 13:00

Location:  Theory Seminar Room 

Speaker:   Johannes Kirscher (George Washington University)

Title:     Universality in Few-Nucleon Systems with a "Pion-less'' Effective Field Theory

Abstract: We present an analysis of bound and scattering properties of three- and four-nucleon systems employing the Effective Field Theory "without pions'' up to next-to-leading order. The focus is on three universal correlations between the triton binding energy and first, the root mean square charge radius of the triton, second, the 4He binding energy, and third, the singlet S-wave 3He-neutron scattering length. Charge symmetry breaking effects are shown in results for the trinucleon binding energy splitting. The results compare favorably with data and values from AV18(+UIX) model calculations and demonstrate the convergence and usefulness of the pionless theory at next-to-leading order in the 4He system, indicating that no four-nucleon force is needed to renormalize the theory at next-to-leading order. We fitted a variety of nucleon-nucleon phase shift equivalent coordinate space potentials with different off-shell behavior for a broad range of cutoff values of the momentum space regulator. In the A=6 system we present results at leading-order in the pionless theory for the binding energy and the average charge radius of 6He for a range of regulator cutoff values. The calculations utilize the Refined Resonating Group Model technique which expands the few-body wave functions in a non-orthogonal basis of Gaussian type. All calculations include a full treatment of the Coulomb interaction and are renormalized with a leading-order three-body contact interaction. We show how the finite variational basis can be utilized as a regulator of the theory and therefore its intertwining with the renormalization of the three- and four-body system through a three-body force. An outlook on future applications of an effective theory with contact interactions only is given. We name big bang nuclear synthesis and cold atom systems as examples apt for a similar investigation presented here for nucleons.



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