Speaker
Description
The strong electromagnetic fields accompaning heavy ions accelerated at BNL and LHC leads to vector meson photoproduction in the ultra-peripheral collisions (UPC), where there is no overlap between the colliding nuclei.
We point out the importance of ultra-peripheral photoproduction of vector meson
in the Coulomb field of nuclei as a means of measuring the radius of the neutral vector
meson due to possibility of two photon exchange. This new contribution to the
production amplitude is small compared to the conventional diffractive amplitude,
but because of large impact parameters inherent to the ultra-peripheral Coulomb
mechanism its impact on the slope in the transfer momenta distribution is substantial.
We predict appreciable and strongly energy dependent increase of the slope
in the vector meson distribution towards very small momentum transfer.The magnitude
of the effect is proportional to the mean radius squared of the vector meson
and is within the reach of high precision photoproduction experiments, which gives
a unique experimental handle on the size of vector mesons.
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