  We consider a QED scattering ($AB\rightarrow AB$), in which $B$ is initially
entangled with a third particle ($C$) that does not participate directly in the
scattering. The effect of the scattering over $C$'s final state is evaluated
and we note coherence (off-diagonal) terms are created, which lead to non null
values for $\langle \sigma_x\rangle$ and $\langle \sigma_y\rangle$ that are, in
principle, measurable in a Stern-Gerlach apparatus. We chose a particular QED
scattering ($e^+e^-\rightarrow\mu^+\mu^-$) and found that $\langle
\sigma_x\rangle$ and $\langle \sigma_y\rangle$ are proportional to the total
cross section ($\sigma_{\text{total}}$) of the $AB$ scattering, besides being
maximal if $BC$'s initial state is taken as a Bell basis. Furthermore, we
calculated the initial and final mutual informations $I_{AC}$ and $I_{BC}$, and
noticed an increase (decrease) in $I_{AC}$ ($I_{BC}$), which indicates that,
after $AB$ interact, the total amount of correlations (quantum $+$ classical)
are distributed among the $3$ subsystems.
