The luminosity measurement at the Belle detector

The processes of e+e−→e+e− and e+e−→γγ are used for the online and offline luminosity measurements at the Belle detector operating at the KEKB collider. The online luminosity is monitored with three independent systems. The obtained statistical accuracy is about 2% for a 10 s measurement with a luminosity of 7×1033 cm−2 s−1. For the offline measurements the events in the barrel part of the detector are used. The total accuracy 1.5% is limited by the theoretical error of the MC simulation.