At 3:55 pm on November 22, Belle accumulated the electron-positron collision data of 500 inverse femto barn (fb-1). This is a landmark integrated luminosity since the beginning of the KEKB accelerator and the Belle experiment in 1999.
 
Integrated luminosity is a measure of the number of particle collisions. The record is equivalent to achieve 5 times 10 to the 41st crossings of electrons and positrons per square centimeter. More than 500 millions of pairs of B- and anti B-mesons are generated in the collisions.
 
Original goal of the KEKB was to achieve 100 inverse femto barn in 3 years. 500 inverse femto barn in 6 and a half years surpasses the original goal, and the group aims to achieve yet higher goals with various types of upgrades to the machine.
 
Belle experiment, consists of about 400 physicists from 15 countries and regions, is trying to study the standard model of the particle physics and the beyond, with the electron and positron collisions generated by KEKB accelerator.