text: This quantity can be estimated using 12 parameters by the Ramsauer model, and in a different context, it is given by the Rosenbluth formula.
full_question: This quantity can be estimated using 12 parameters by the Ramsauer model, and in a different context, it is given by the Rosenbluth formula. Its value due to the presence of a charge distribution equals its value due to an equivalent point charge times the square of the form factor. The formula for this quantity is modified by two "structure functions" which are functions of the square of the momentum transfer and the energy transfer in a phenomenon called Bjorken scaling. This quantity equals 4 pi divided by the wave vector times the imaginary part of "f of zero" according to the optical theorem. The mean free path is the inverse of the "macroscopic" form of this quantity, which equals the number of particles per unit volume times its "microscopic" form. This quantity is equal to the square of the scattering amplitude, and for a sphere it equals pi times the radius of the sphere squared. It is often given in units of barns. For 10 points, name this quantity denoted sigma which represents an effective area characterizing a particle interaction.
first_sentence: This quantity can be estimated using 12 parameters by the Ramsauer model, and in a different context, it is given by the Rosenbluth formula.
raw_answer: cross section [or differential cross section; or total cross section; or macroscopic cross section; or microscopic cross section; or scattering cross section; prompt on "effective area"]