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Abstract:

The status of R&D on hardware components of fast beam-based feedback systems is described. The main developments are being pursued by the Feedback On Nanosecond Timescales (FONT) and Feedback at High Energy Requirements (FEATHER) groups based in the UK/SLAC and in Japan, respectively. The FONT2 and FONT3 experimental results are summarised, and plans are outlined for FONT4.

Abstract:

We report preliminary results of beam tests of the FONT3 Linear Collider intra-train position feedback system prototype at the Accelerator Test Facility at KEK. The feedback system incorporates a novel beam position monitor (BPM) processor with a latency below 5 nanoseconds, and a kicker driver amplifier with similar low latency. The 56 nanosecond-long bunchtrain in the ATF extraction line was used to test the prototype BPM processor. The achieved latency will allow a demonstration of intra-train feedback on timescales relevant even for the CLIC Linear Collider design. © 2005 IEEE.

Abstract:

We measure the hadronic branching ratios of the Z0 boson into heavy quarks: Rb=ΓZ0→bb̄/ΓZ0→hadrons and Rc= ΓZ0→cc̄/ΓZ0→hadrons using a multitag technique. The measurement was performed using about 400000 hadronic Z0 events recorded in the SLC Large Detector experiment at SLAC between 1996 and 1998. The small and stable SLAC Linear Collider beam spot and the CCD-based vertex detector were used to reconstruct bottom and charm hadron decay vertices with high efficiency and purity, which enables us to measure most efficiencies from data. We obtain, Rb=0.21604±0.00098(stat.)±0.00073(syst.)0.00012(Rc) and, Rc=0.1744±0.0031(stat.)±0.0020(syst.)0.0006(Rb). © 2005 The American Physical Society.