content_image/356678.jpg content_image/356684.jpg content_image/356685.jpg content_image/356683.jpg
gluon D -form factor as 

<img src='content_image/356678.jpg'>

Thus the maximal amount of information on gluon GPDs which can be extracted from the leading order gluon amplitude of hard exclusive electroproduction of J PC = 1 −− mesons can be quantified in terms of gluon GPD quintessence functions N g ( E,M ) and the value of gluon D - form factor D g or, equivalently, in terms of N g ( E, M ) and G ( E ) 0 . The method of the Abel transform tomography for the dual parametrization of GPDs suggested in [16] allows to invert the integral convolutions for the imaginary parts of the elementary amplitudes in order to recover GPD quintessence functions. The generalization of this method for the case of gluon GPDs is straightforward. The expressions for gluon electric and magnetic GPD quintessence functions through the imaginary parts of the corresponding elementary amplitudes (41) read: 

<img src='content_image/356684.jpg'>

<img src='content_image/356685.jpg'>

It is also extremely instructive to consider the small- ξ asymptotic behavior of Im A g ( E,M $^{)}$( ξ ) in the framework of the dual parametrization. Assuming the power law behav- ior N ( E, M $^{)}$( x ) ∼ 1 x α for gluon electric and magnetic GPD quintessence functions for small x we obtain for ξ ∼ 0: 

<img src='content_image/356683.jpg'>

The case of particular importance is the so-called minimalist dual model in which only the contributions of the forward like functions G ( E,M ) 0 ( x ) (36) are taken into account. Let 

