Scattering amplitudes at multi TeV energies

Abstract

We show that a generalized Regge behaviour, $$Im F(s,t)\simeq \Phi(t)(\log s/\hat{s})^{\nu(t)}(s/\hat{s})^{\alpha_P(t)},\quad{\rm for} |t|<|t_0|, s\to\infty$$ where $\Phi(t)\simeq e^{bt}$, $\alpha_P(t)\simeq \alpha_P(0)+\alpha'_P(0)t$, and $t_0$ is the first zero of $\alpha_P(t)$, $\alpha_P(t_0)=0$, implies that the corresponding cross section is bounded by $$\sigma_{\rm tot}(s)<({\rm Const.})\times\log s/\hat{s}.$$ This growth, however, is not sufficient to fit the experimental cross sections. If, instead of this, we assume saturation of the improved Froissart bound, i.e., a behaviour $$Im F(s,0)\simeq A(s/\hat{s})\log^2{{s}\over{s_1\log^{7/2} s/s_2}}, $$ a good fit is obtained to $\pi\pi$, $\pi N$, $KN$ and $NN$ cross sections from c.m. kinetic energy $E_{\rm kin}\simeq1 $ GeV to 30 TeV (producing a cross section of $108\pm6$ mb at LHC energy). This suggests that the Regge-type behaviour only holds for values of the momentum transfer very near zero.