Electron-Proton Scattering. Deep Inelastic Region

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 q 2 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 q 2 the behavior depends theoretically on the angular momentum of the state and starts as an appropriate power of Q (Q 2 = -q 2 ).