x, y, and Q2

x : in the parton model is the fraction of the nucleon or nucleus momentum carried by the struck parton.

y : is the fraction of the lepton's energy lost in the nucleon rest frame. It it thus also the fraction of the incoming lepton energy (also known as inelasticity) carried by the exchange boson in the rest frame of the nucleon.

Q2 : is the negative square of the momentum transfer q and denotes the virtuality of the exchanged gauge boson. The momentum transfer q determines the size of the wavelength of the virtual boson and therefore the object size which can be resolved in the scattering process. Better resolution requires smaller wave lengths of the virtual boson and therefore larger momentum transfers. Q2 can be interpreted as the resolution power of the scatter.

x, y, and Q2 are related via:

Note that when neglecting the lepton and the proton mass the equation simplifies to Q2=xys. In eDISK we use the complete formula above.