Gluon Bremsstrahlung and Double Parton Scattering in pp Collisions at Sqrt S=63 GeV

摘要

We study 3-jet and 4-jet events in pp collisions at sqrt s=63 GeV. From the observed 3-jet/2-jet yield ratio the strong coupling is determined to lowest order alpha /sub S/=0.18 +- 0.03 +- 0.04 (syst). The 4-jet events are found to be dominantly due to double parton scattering (DPS) rather than double bremsstrahlung. From the observed DPS/2-jet yield ratio and a simple model for the multi-parton structure of the proton, we deduce the proton radius r=0.3 fm, characterising the average transverse separation of partons at x=0.2-0.3. (ERA citation 12:027742)