Min-Bias at the Tevatron

As illustrated in Fig. 1, the total proton-antiproton cross section is the sum of the elastic and inelastic components, σ_tot = σ_EL + σ_IN. The inelastic cross section consists of three terms; single diffraction, double-diffraction, and everything else (referred to as the 'hard core'), σ_IN = σ_SD + σ_DD + σ_HC. For elastic scattering neither of the beam particles breaks apart (i.e. color singlet exchange). For single and double diffraction one or both of the beam particles are excited into a high mass color singlet state (i.e. N* states) which then decays. Single and double diffraction also corresponds to color singlet exchange between the beam hadrons. When color is exchanged the outgoing remnants are no longer color singlets and one has a separation of color resulting in a multitude of quark-antiquark pairs being pulled out of the vacuum. The 'hard core' component, σ_HC, involves color exchange and the separation of color. However, the 'hard core' contribution has both a 'soft' and 'hard' component. Most of the time the color exchange between partons in the beam hadrons occurs through a soft interaction (i.e. no high transverse momentum) and the two beam hadrons 'ooze' through each other producing lots of soft particles with a uniform distribution in rapidity and many particles flying down the beam pipe. Occasionally there is a hard scattering among the constituent partons producing outgoing particles and 'jets' with high transverse momentum