The ability to
study hard diffraction in bins of momentum transfer is another crucial
advantage provided by
the FPD. The momentum transfer to the proton is
equal to the momentum transfer of the pomeron, and there is a simple
relation between the momentum transfer and the
angle 
of the scattered proton
.
Current phenomenology assumes that the slope
of 
is the same as for soft diffraction, but this
requires verification.
It is quite possible that a phase transition in
the behavior of the pomeron occurs above some |t| threshold.
At low |t|, the pomeron structure may be significantly softer (that is,
peaked at lower 
) than at higher |t|, where it
may have a hard two gluon or two quark structure which results
in intermediate , or a super-hard structure
(like a single gluon) which results in a distribution
peaked near one.