PT Journal
AU Cirigliano, V
   Jenkins, JP
   Gonzalez-Alonso, M
TI Semileptonic decays of light quarks beyond the Standard Model
SO Nuclear Physics B
JI Nucl. Phys. B
PY 2010
BP 95
EP 115
VL 830
IS 1-2
DI 10.1016/j.nuclphysb.2009.12.020
LA English
DE Semileptonic decays; CKM unitarity; Effective theory; Beyond the Standard Model
AB We describe non-standard contributions to semileptonic processes in a model independent way in terms of in SU(2)(L) x U(1)(Y) invariant effective lagrangian at the weak scale, front which we derive the low-energy effective lagrangian governing muon and beta decays. We find that the deviation from Cabibbo universality, Delta(CKM) equivalent to vertical bar V-ud vertical bar(2) + vertical bar V-us vertical bar(2) + vertical bar V-ub vertical bar(2) – 1, receives contributions from four effective operators. The phenomenological bound Delta(CKM) = (-1 +/- 6) x 10(-4) provides strong constraints on all four operators, corresponding to art effective scale Lambda > 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 Delta(CKM) = -0.01 (90% CL). An observed Delta(CKM) not equal 0 at this level Could be explained in terms of a single four-fermion operator which is relatively poorly constrained by electroweak precision measurements.
ER