content_image/342986.jpg content_image/342989.jpg content_image/342990.jpg content_image/342991.jpg content_image/342992.jpg
the following general TNF 

a generic term can be put in the following form: 

<img src='content_image/342986.jpg'>

<img src='content_image/342989.jpg'>

Each term corresponds to a different mechanism and has a different operatorial structure. The first three terms arise from the exchange of two pions between three nucleons. The a -term comes from πN S -wave scattering whereas the b -term and d -term, which are the most important, come from πN P -wave scattering. The specific form of these three terms in configuration space is the following: 

<img src='content_image/342990.jpg'>

with W 0 an overall strength. The b - and d -terms are present in the three models whereas the a -term is present in the TM’ and N2LOL and not in URIX. In the first two models, the radial functions y ( r ) and t ( r ) are obtained from the following function 

where m$_{π}$ is the pion mass and 

<img src='content_image/342991.jpg'>

<img src='content_image/342992.jpg'>

The cutoff function F Λ in the TM’ or Brazil models is taken as F Λ = [(Λ 2 − m 2 $_{π}$) / (Λ $^{2}$+ q $^{2}$)]$^{2}$. In the N2LOL model it is taken as F Λ = exp( − q $^{4}$/ Λ $^{4}$). The momentum cutoff Λ is a 

