NEGATIVE MOMENTUM COMPACTION AT KEKB

Abstract KEKB [1] is a high luminosity e + e - collider for studying B mesons and has achieved the design luminosity of 10 34 cm -2 s -1 in 2003. In order to get higher luminosity, we tested negative momentum compaction optics 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 compaction optics. INTRODUCTION KEKB is an e + e - collider for the B meson physics 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 luminosity in the world. KEKB achieved 10.57 /nb/s on May 13th, 2003. Figure 3 shows the integrated luminosity of KEKB. We logged more than 150 /fb luminosity by 2003 summer. Figure 1: KEKB Accelerator. Table 1 compares the major machine parameters between design value and the value when the best peak luminosity was achieved in 2003 summer. In order to get higher luminosity, β