If the $z$-parameterization is defined with $t_0=0$, then $z(q^2=0)=0$ and the kinematic constraint f+(0)=f0(0) translates into $a_0^0=a_0^+$. This special case has not been covered by the BCL implementation so far, which is fixed in this PR.
In addition, an optional chiral logarithm factor (as e.g. used in arXiv:2207.12468) is introduced.
If the $z$-parameterization is defined with $t_0=0$, then $z(q^2=0)=0$ and the kinematic constraint f+(0)=f0(0) translates into $a_0^0=a_0^+$. This special case has not been covered by the BCL implementation so far, which is fixed in this PR. In addition, an optional chiral logarithm factor (as e.g. used in arXiv:2207.12468) is introduced.