following way: W 0 = 1 12 π 2 ( m$_{π}$ F$_{π}$ ) 4 g 2 $_{A}$m 2 π W D 0 = 1 12 π 2 ( m$_{π}$ F$_{π}$ ) $^{4}$( m$_{π}$ Λ$_{x}$ ) g$_{A}$m$_{π}$ 8 W E 0 = 1 12 π 2 ( m$_{π}$ F$_{π}$ ) $^{4}$( m$_{π}$ Λ$_{x}$ ) m$_{π}$ (12) with a = c 1 m 2 $_{π}$, b = c 3 / 2, d = c 4 / 4, and c 1 = − 0 . 00081 MeV − $^{1}$, c 3 = − 0 . 0032 MeV − $^{1}$, c 4 = − 0 . 0054 MeV − 1 taken from Ref. [15]. The other two constants, c$_{D}$ = 1 . 0 and c$_{E}$ = − 0 . 029, have been determined in Ref. [10] from a fit to B ( $^{3}$H) and B ( $^{4}$He) using the N3LO- Idaho+N2LOL potential model. The numerical values of the constant entering in W 0 , W D 0 and W E 0 are m$_{π}$ = 138 MeV, F$_{π}$ = 92 . 4 MeV, g$_{A}$ = 1 . 29, and the chiral symmetry breaking scale Λ$_{x}$ = 700 MeV. In order to analyze the different short range structure of the TNF models, in Fig. 1 we compare the dimensionless functions Z 0 ( r ), y ( r ) and T ( r ) for the three models under consideration. In the TM’ model using the definition of Eq.(10) and using the corresponding cutoff function we can define: This function is showed in the first panel of Fig. 1 as a dashed line. From the figure we can see that, in the case of the URIX model, the functions Z 0 ( r ) and y ( r ) go to zero as r → 0. This is not the case for the other two models and is a consequence of the regularization choice of the Y and T functions adopted in the URIX. In this section we study possible variations to the parametrization of the TNF models in order to describe the A = 3 , 4 binding energies and $^{2}$a$_{nd}$ . We first study the TM’ potential and we would like to see whether, using the AV18+TM’ interaction, it is possible to reproduce simultaneously the triton binding energy and the A. Tucson-Melbourne Force III. PARAMETRIZATION STUDY OF THE THREE NUCLEON FORCES 8 Z T M 0 ( r ) = 12 π m 3 π 1 2 π 2 ∫ ∞ 0 dqq $^{2}$j 0 ( qr ) ( Λ 2 − m 2 π Λ 2 + q 2 ) 2 = 3 2 ( m$_{π}$ Λ ) ( Λ 2 m 2 π − 1 ) 2 e − Λ r . (13)