The longitudinal and transverse spin response functions which Alberico, et al. [AEM82] predicted would be modified by an enhancement in the nuclear pion field, are given by [Bro95]
and
respectively, where 
and 
are the initial (final) wavefunctions and energy of the nucleons,
respectively.
The spin response functions describe the response of the nucleus to the
various spin operators,
where 
is the spin of the nucleon and 
is the
momentum transfer.
In terms of these response functions the nucleon-nucleus (nA) cross section
can be written as
where 
are the free nn partial differential cross sections and
0, i, j, and k are a complete basis for describing the nucleon
polarization.
Equation 
illustrates the meaning of the nuclear response
function as a quantitative measure of the effect that the collective action
of the nucleus has on scattering. The response functions describe how the
free nn scattering is altered in nA scattering.
To obtain these response functions experimentally it is necessary to
make a polarization transfer measurement of a target, which requires
knowing the polarization of both the incident and ejected nucleon to
determine how the spin is affected by interaction with the nucleus. Once
the polarization transfer observables are measured it is possible to use
them to
determine the spin-response functions [IcK92]. This procedure will
be elaborated upon in chapter .
