NEGATIVE MOMENTUM COMPACTION AT KEKB

Abstract KEKB[1] is a high luminositye + e - collider for studying B mesonsand has achieved the design luminosityof 10 34 cm -2 s -1 in 2003. In order to get higher luminosity, we tested negative momentum compactionoptics in the summer of 2003. We measured the bunch length using three methods at 0.7mA to 1.17mA bunch current and confirmed the length was shortened with the negative momentum compactionoptics. INTRODUCTION KEKBis an e + e - collider for the B mesonphysics consisting of an electron ring of 8 GeV (HER) and a positron ring of 3.5 GeV (LER) as shown in Figure1. Figure 2 shows the trend of peak luminosityin the world. KEKBachieved 10.57 /nb/s on May 13th, 2003. Figure 3 shows the integrated luminosityof KEKB. We logged more than 150 /fb luminosityby 2003 summer. Figure 1: KEKBAccelerator. Table 1 compares the major machine parameters between design value and the value when the best peak luminositywas achieved in 2003 summer. In order to get higher luminosity, β