Three-Nucleon Force Effects in p-H(3) and n-He(3) scattering

We present a preliminary study of the effect of a three-nucleon force (3NF) in p-H(3) and n-He(3) scattering at low energies. The used 3NF is derived from effective field theory at next-to-next-to-leading order. The four-nucleon scattering observables are calculated using the Kohn variational principle and the hyperspherical harmonics technique and the results are compared with available experimental data. We have found that the effect of introducing this type of 3NF is tiny, and sometimes worsens the agreement with the experimental data