Nuclear Physics Seminars

ics Nuclear
Tuesday, May 3, 2016
3:30 PM
Physics Building, Room 204
Charlie Glaser
UVA-Department of Physics
" Precise Determination of the Pion Electronic Decay Branching Ratio"
 Slideshow (PDF)

The ratio of decay rates \(\Gamma(\pi{\to}ev^{-}(\gamma))/\Gamma(\pi{\to}{\mu}v^-(\gamma))\) provides a key confirmation of the V−A nature of the electroweak interaction. Currently, the experimenally determined value of this ratio is\(R^{exp}_{e/\mu} = (1.230\pm0.004)\times10^{-4}\), whereas the theoretically determined value according to Standard Model physics is \(R^{SM}_{e/\mu} = (1.2356\pm0.0001)\times10^{-4}\). This \(\pi_{2e}\) branching ratio proves one of the most sensitive tests for lepton universality. The branching ratio can also be used to give mass bounds on “new” , or non V−A, particles e/µ and interactions. It is for this reason the PEN group, an international collaboration led by University of Virginia, has undertaken to measure \(R^{exp}_{e/\mu}\) to a precision of 5 × \(10^{-4}\) or better. I will discuss the challenges and analysis techniques to extract \(\pi_{2e}\) branching ratio with more emphasis on the Monte Carlo simulation that aids in determining necessary quantities for branching ratio extraction.



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