D. H. Brown | Searcharxiv

arXiv1996

A Scintillating Fiber Hodoscope for a Bremstrahlung Luminosity Monitor at an Electron$-$Positron Collider

The performance of a scintillating fiber (2mm diameter) position sensitive detector ($4.8 \times 4.8$ cm$^2$ active area) for the single bremstrahlung luminosity monitor at the VEPP-2M electron-positron collider in Novosibirsk, Russia is described. Custom electronics is triggered by coincident hits in the X and Y planes of 24 fibers each, and reduces 64 PMT signals to a 10 bit (X,Y) address. Hits are accumulated (10 kHz) in memory and display (few Hz) the VEPP-2M collision vertex. Fitting the strongly peaked distribution ( $\sim$ 3-4 mm at 1.6m from the collision vertex of VEPP-2M ) to the expected QED angular distribution yields a background in agreement with an independent determination of the VEPP-2M luminosity.

acc-phys↗

arXiv1996

The Lowest Order Hadronic Contribution to the Muon $g-2$ Value with Systematic Error Correlations

We have performed a new evaluation of the hadronic contribution to $a_μ=(g-2)/2$ of the muon with explicit correlations of systematic errors among the experimental data on $σ( e^+e^- \to hadrons )$. Our result for the lowest order hadronic vacuum polarization contribution is $ a_μ^{had} = 702.6(7.8)(14.0) \times 10^{-10}$ where the the first error is statistical and the second is systematic. The total systematic error contributions from below and above $\sqrt{s} = 1.4$ GeV are $(13.1) \times 10^{-10}$ and $(5.1) \times 10^{-10}$ respectively, and are hence dominated by the low energy region. Therefore, new measurements on $σ( e^+e^- \to hadrons )$ below 1.4 GeV can significantly reduce the total error on $a_μ^{had}$. In particular, the effect on the total errors of new hypothetical data with 3 \% statistical and 0.5 - 1.0 \% systematic errors is presented.

hep-ph↗