Calibrating 3-body nuclear forces

  Sergiu Lupu  ,  Doron Gazit  ,  Nir Barnea  
Hebrew University

Is there an elegant, symmetry based theory that can capture the diversity of nuclear phenomena? The underlying structure of the nucleus is described by QCD in terms of quarks and glouns. However, nuclear processes take place at the low energy regime where the non-perturbative nature of QCD makes predictions a very difficult task. Instead, an effective field theory approach called Chiral-EFT is taken, identifying nucleons and pions as the relevant degrees of freedom and writing the most general Lagrangian invariant under the symmetries of QCD. Chiral-EFT, as a low momentum theory, prescribes a scheme for ordering the terms of the Lagrangian according to their importance and so the precision of the calculation is controlled. 3-body forces first appear at next-to-next-to-leading order (N2LO) with unconstrained coefficients called Low Energy Constants (LEC). Here we present constraints on these LECs by calculating Triton’s binding energy and beta decay. The calculations were done using N3LO 2-body potential [Machleidt & Entem,2011] or Vlowk, a soft version of this potential [Bogner et al.,2003] with N2LO 3-body potential [van Klock,1996]. As a first test case we present predictions, without free parameters, for 4He binding energy and its first resonance.