## Nuclear Physics Seminars

 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) ABSTRACT: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. SLIDESHOW:

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