Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1841462 | Nuclear Physics B | 2010 | 21 Pages |
Abstract
We describe non-standard contributions to semileptonic processes in a model independent way in terms of an SU(2)LÃU(1)Y invariant effective lagrangian at the weak scale, from which we derive the low-energy effective lagrangian governing muon and beta decays. We find that the deviation from Cabibbo universality, ÎCKMâ¡|Vud|2+|Vus|2+|Vub|2â1, receives contributions from four effective operators. The phenomenological bound ÎCKM=(â1±6)Ã10â4 provides strong constraints on all four operators, corresponding to an effective scale Î>11 TeV (90% CL). Depending on the operator, this constraint is at the same level or better then the Z pole observables. Conversely, precision electroweak constraints alone would allow universality violations as large as ÎCKM=â0.01 (90% CL). An observed ÎCKMâ 0 at this level could be explained in terms of a single four-fermion operator which is relatively poorly constrained by electroweak precision measurements.
Related Topics
Physical Sciences and Engineering
Mathematics
Mathematical Physics
Authors
Vincenzo Cirigliano, James P. Jenkins, MartÃn González-Alonso,