study as has been done previously for the other TNF models. Fixing the constant c 1 to its original value c 0 $_{1}$, c 3 , c 4 , c$_{D}$ and c$_{E}$ have been varied. The analysis is shown in Fig. 6 at the following four values of c$_{E}$ = 0 , 0 . 1 , − 0 . 03 , − 0 . 5 and for the indicated values of c$_{D}$ chosen to reproduce $^{2}$a$_{nd}$ (left panels). The predictions for B ( $^{4}$He) are given in the right panels for those values of the parameters that give a value of $^{2}$a$_{nd}$ inside the box. At each point of the curves in the left panels and at the points in the right panels, c 4 has been chosen to reproduce the triton binding energy. Due to the ( $^{τ}$i · τ $_{j}$) operator in the E -term of the N2LOL potential, positive values of c$_{E}$ makes this term attractive. Conversely, negative values of c$_{E}$ makes this term repulsive. We have considered only one positive case, c$_{E}$ = 0 . 1. Increasing further c$_{E}$ we found it difficult to describe correctly B ( $^{4}$He). For negatives values of c$_{E}$ we have considered two cases, c$_{E}$ = − 0 . 03, which corresponds to the value given in Ref. [10], and c$_{E}$ = − 0 . 5. From the figure we observe an almost linear behavior of $^{2}$a$_{nd}$ . There is a slight curvature for negative values of c$_{D}$ in the upper three panels. The analysis of B ( $^{4}$He) selects the values of c$_{D}$ . We have found that the experimental value is well reproduced for the pairs ( c$_{D}$ = − 0 . 5 , c$_{E}$ = 0 . 1), ( c$_{D}$ = − 1 , c$_{E}$ = 0), ( c$_{D}$ = − 1 , c$_{E}$ = − 0 . 03), and ( c$_{D}$ = − 2 , c$_{E}$ = − 0 . 5). In Table IV we report the mean values of the kinetic energy, the two-nucleon potential energy as well as the mean values of the attractive part of the TNF, V$_{A}$ (3 N ), and its repulsive part V$_{R}$ (3 N ) for the selected values of the parameters that correspond to the best description of the three quantities under study. In the last two columns of the table, B ( $^{4}$He) and $^{2}$a$_{nd}$ are given. The contributions to V$_{A}$ (3 N ) come from the a -, b -, d and D -terms, which are always attractive in the cases considered, and from the E -term in the first case. This term contributes to the repulsive part V$_{R}$ (3 N ) in the last two cases. From the table we may observe that c 3 and c 4 results to be larger and smaller than their original values, respectively. This is a consequence of the simultaneous description of B ( $^{3}$H) and $^{2}$a$_{nd}$ . Furthermore, in the first three cases, the ratio c 4 /c 3 ≈ 0 . 46, is much smaller than the original ratio. IV. ANALYSIS OF THE POLARIZATION OBSERVABLES In the previous section we have studied different parametrizations of the TM’, URIX and N2LOL TNF models in conjunction with the AV18 NN potential. The analysis has been done varying the parameters in order first to reproduce B ( $^{3}$H) and then looking at 13