G.J. Lolos et al.: Medium Modifications of Vector Mesons i 
Abstract 
We propose to investigate the subthreshold photoproduction of the three lowest 
mass vector mesons, V = ae 0 , !, and OE mesons. In the subthreshold energy region, 
defined here as the energy region belowthefl+N ! V +N reaction threshold on the 
free nucleon, VMD­driven vector meson production is suppressed and the influence 
of hadronic matter on the masses of the vector mesons is emphasized. This method 
is the optimum vehicle for the study of in­medium modifications and, specifically for 
the ae 0 meson, experimental evidence already exists for a dramatic reduction in m ae o , 
which is dependent on the incident photon energy or the ae 0 
s a means to separate nucleonic from nuclear (mean field) 
effects. This assertion will be tested for the ae 0 
! ß + ß 
explored. 
An attractive nuclear target for this investigation is 3 He. The minimum trigger 
requirement is the detection of twocharged particles (with an open neutral trigger). 
We request 420 hours of nominal tagger photon beam ( 10 7 fl=s ) in Hall B, in the 
tagged photon region between 320 MeV and 1520 MeV, of which 150 hours can be 
collected in the already approved g3 period. 
This is a Hall B Collaboration experiment.