ABSTRACT
Electron beams permit to study reactions such as e p → e x where x is some hadron final state. In addition, very energetic (high mass) states x can be excited in the high energy machines. A great deal of information is becoming available, and there are many theoretical questions especially for the new large q2 and high mass states x. The simplest experiments to do are those which do not require studying the x states at all but just study the electron beam – its deflection and energy determines the momentum transfer and its energy loss determines the energy of x above the proton mass. At very low q2 the behavior depends theoretically on the angular momentum of the state and starts as an appropriate power of Q (Q2 = -q2).
