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Constraints on Muon Decay Parameters from Neutrino Mass. Rebecca J. Erwin Jennifer E. Kile M. Ramsey-Musolf Peng Wang California Institute of Technology. The Big Picture. Neutrinos have mass: new physics! Approaches: number of flavors, mass scale, mixing, Dirac vs. Majorana, . . .
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Constraints on Muon Decay Parameters from Neutrino Mass Rebecca J. Erwin Jennifer E. Kile M. Ramsey-Musolf Peng Wang California Institute of Technology Rebecca Erwin, Panic05, October 24-28, Santa Fe, NM
The Big Picture • Neutrinos have mass: new physics! • Approaches: • number of flavors, mass scale, mixing, Dirac vs. Majorana, . . . • effects on astrophysical and particle physics processes. For example . . . • Can relate ν mass to muon decay • experimental limits on νmass → interesting constraints on μ decay parameters Rebecca Erwin, Panic05, October 24-28, Santa Fe, NM
Outline • μ-decay: Michel parameters • parameterize contributions to μ-decay from beyond the Standard Model • Connecting μ-decay and ν mass* • “chirality-changing” operators that contribute to both processes • operator mixing • Implications for the TWIST experiment • ν mass puts strong constraints on some contributions to the MPs *Prézeau and Kurylov, PRL 95 (2005) Rebecca Erwin, Panic05, October 24-28, Santa Fe, NM
μ-decay: Michel Parameters , … , ... • Michel parameters (ρ, η, δ, ξ, . . . ) are bilinear combinations of the coupling constants g • Standard Model: • Other gs nonzero in many beyond-the-SM models Rebecca Erwin, Panic05, October 24-28, Santa Fe, NM
Connecting μ-decay and ν Mass Rebecca Erwin, Panic05, October 24-28, Santa Fe, NM
What Goes In: Our Calculation • Different operators contribute to different Michel parameters • Combined with . . . • Lots of operator mixings → lots of diagrams Rebecca Erwin, Panic05, October 24-28, Santa Fe, NM
What Comes Out: Implications for TWIST • At current experimental limits, any deviation from SM values will not come from ν mass! * Gagliardi, Tribble, Williams, hep-ph/0509069 Rebecca Erwin, Panic05, October 24-28, Santa Fe, NM
Summary • Michel parameters describe contributions to μ-decay from beyond SM • Can use experimental limits on neutrino mass to constrain the Michel parameters • Resulting constraints much smaller than current experimental limits • Future research: • Majorana case, β-decay, . . . Rebecca Erwin, Panic05, October 24-28, Santa Fe, NM