Speaker: Vladimir Braun (Regensburg University)

Title: Exclusive Processes in Position Space and the Pion 
	Distribution Amplitude

Abstract:
 We suggest to carry out  lattice calculations of current
correlators in position space, sandwiched between the vacuum and a
hadron state (e.g.~pion), in order to access hadronic light-cone
distribution amplitudes (DAs). In this way the renormalization
problem for composite lattice operators is avoided altogether, and
the connection to the DA is done using perturbation theory in the
continuum. As an example, the correlation function of two
electromagnetic currents is calculated to the
next-to-next-to-leading order accuracy in perturbation theory and
including the twist-4 corrections. We argue that this strategy is
fully competitive with direct lattice measurements of the moments
of the DA, defined as matrix elements of local operators, and
offers new insight in the space-time picture of hard exclusive
reactions.