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The relation obtained in Eq. (7.9) illustrates two important findings. First, it shows
that for low missing momenta (small δω) the degree of off-shellness wil be smaller
than for the higher missing momentum range. Second, it indicates that the ambiguities
decrease as q and ω increase, thereby making the ratio equal to one.
An interesting physical observable in the context of off-shell effects is the left-right
asymmetry, whose Q 2 evolution also confirms the above behaviour. This particular
observable is interesting in that it reflects the behaviour of the R T L response
function. Fig. 7.8 shows the left-right asymmetry for the 12 C(e, e ′ p) 11 B(1p −1
3/2 ) reaction
at four different energies under quasielastic conditions. Indeed, the ambiguities
decrease with increasing momentum transfers, and are more significant for higher
missing momenta. This concurs with the findings of Ref. [42]. The left-right asymmetry
does not depend on spectroscopic factors and has frequently been illustrated
to be extremely sensitive to the various ingredients that enter the model calculations.
As such it is an interesting variable for discriminating for example between
the different gauge choices. Fig. 7.9 shows our predictions for A LT at Q 2 = 0.8
(GeV/c) 2 . We have performed optical potential and Glauber calculations, considering
both the CC1 and CC2 current operator. At first sight, it appears that the
data favor the calculations using the CC2 current operator. The CC1 calculations
tend to overestimate the measured left-right asymmetry. For the 1p 1/2 knockout the
overall agreement is satisfactory. It is remarkable that for a particular choice for the
current operator, the Glauber and optical potential model produce A LT ’s that are
close at missing momenta below the Fermi momentum. Once again, it emerges that
the optical potential and the Glauber model, despite their very different starting
points, yield results that are remarkably similar.