Hadron form factors from sum rules for vacuum-to-hadron correlators

摘要

We analyse the extraction of the bound-state form factor from vacuum-to-hadron correlator, which is thebasic object for the calculation of hadron form factors in the method of light-cone sum rules in QCD.We study this correlator in quantum mechanics, calculate it exactly, and derive the corresponding OPE.We then apply the standard procedures of QCD sum rules to isolate the ground-state form factor fromthis correlator. We demonstrate that fixing the effective continuum threshold, one of the key ingredientsof the sum-rule calculation of bound-state parameters, poses a serious problem for sum rules based onvacuum-to-hadron correlators.