is the signature factor for Regge pole $i$ with trajectory $\alpha_i(t)$ and signature $\sigma_i = \pm1$. The vertex factors $g_{13}(t_1)$ and $g_{24}(t_2)$ describe the $13-\alpha_i$ and $24-\alpha_k$ couplings respectively, while $g_{ik}^h$ describes the transition $\alpha_i\alpha_k\to h$. Note that $g_{ik}^h$ depends, in general, on all the scalars that can be formed from the vectors which enter the vertex. Moreover, in the case of Reggeons, the longitudinal and transverse components of their momenta act as two different vectors [@a10]. In our case, where the mass of the boson $h$ is fixed, it is enough to keep the transverse momenta $\vec p_{3\perp}$ and $\vec p_{4\perp}$, and the unit vector $\vec n_0$ in the direction of the colliding hadrons. Unlike $g_{13}$ and $g_{24}$, the function $g_{ik}^h$ may be complex. In the Regge domain [(\[eq:bear\])]{}, s\_1s\_2 = s(m\_h\^2 + p\_[h]{}\^2), \[eq:elephant\] where $s = (p_1 + p_2)^2$.

When spin is included, the process is described by helicity amplitudes, each of which has a double-Regge behaviour as in [(\[eq:cat\])]{} [@a11]. T\_[\_1\_2]{}\^[\_3\_h\_4]{}(s\_1,s\_2,t\_1,t\_2,) = \_[i,k]{}g\_[\_1\_3]{}(t\_1)g\_[\_2\_4]{}(t\_2) ()\^[\_i(t\_1)]{}()\^[\_k(t\_2)]{} (\_i(t\_1))(\_k(t\_2))g\_[ik]{}\^[\_h]{}(t\_1,t\_2,) \[eq:fox\] The relations between the vertex couplings for different helicities, due to conservation of parity and other quantum numbers, are the same as for $2\to2$ reaction [@a12]. For example, g\_[\_1\_3]{}(t) = 