  The collective observables play critical roles in probing the properties of
quark-gluon-plasma created in relativistic heavy-ion collisions, in which the
information on initial collision geometry is crucial. However, the initial
collision geometry, e.g., the reaction plane, cannot be directly extracted in
the experiment. In this paper, we demonstrate the idea of determining the
reaction plane via the feature of linear polarization of the coherent
photoproduction process and discuss the advantages of the proposed approach in
comparison with traditional methods.
