A measurable form of this quantity is given by the convolution of parton (“PAR-tawn”) distribution functions with the “hard” form of it. This quantity is given by the following: “one over the flux factor,” times the integral over Lorentz-invariant phase space of “some delta functions times the squared magnitude of the amplitude, denoted capital M.” In partial wave analysis, this quantity is: “four pi over k squared,” times the sum over L of the expression: “2L plus one,” all times “sine-squared of the Lth phase shift.” This quantity equals “four pi over the wave number,” all times the “imaginary part of the scattering amplitude evaluated at 0” by the optical theorem. This quantity equals the integral over the solid angle of its differential, which is a function of the impact parameter and scattering angle. For 10 points, name this quantity that is the area of the target as seen by the incoming particle in a scattering process. ■END■
ANSWER: cross section [accept total cross section or integrated cross section or scattering cross section; accept partonic cross section, parton-parton cross section, parton collision cross section, or hard-scattering cross section; accept Lorentz-invariant cross section; after “differential” is read, accept differential cross section; until “differential” is read, reject “differential cross section”; reject any other more specific forms of cross section]
<Physics>
= Average correct buzz position