|V_{cd}|, |V_{cs}| and f_{D_s} from (semi) leptonic $D_{(s)}$-decays : signals of New Physics ?

Stéphan Narison (1)

1 LPTA - Laboratoire de Physique Théorique et Astroparticules

We confront the recent improved measurements of the D_{(s)} (semi) leptonicdecays with lattice QCD (LQCD) with n_f=3 flavours and QCD spectral sum rules(QSSR) predictions. D\to\mu\nu_\mu leptonic width data compared withtheoretical determinations of f_D, leads to the value of the CKM mixing angle :|V_cd|= 0.230 (10)_exp (9)_th. Measured ratio of the D semi-leptonic widthscombined with LQCD and QSSR predictions leads to the average |V_cd|/|V_cs|=0.2175(88), and then to |V_cs|= 1.068(47). We consider the previousdeterminations as improvements of the existing estimates. Using the averagedata of the D_s\to \mu\nu_\mu (resp. D_s\to \tau\nu_\tau) branching ratios, oneobtains : |V_cs|f_{D_s}^\mu= (259 +- 12) {MeV} (resp) |V_cs|f_{D_s}^\tau= (274+- 13) {MeV}, which can be compared with the average of the Standard Model (SM)values from LQCD and QSSR f_{D_s}=(240 +- 7) MeV. If one uses the presentdetermination of |V_cs|, there is an agreement with the SM prediction within1\sigma. If instead, we impose the unitarity constraint |V_cs|< 1, or assume(as frequently done) |V_cs|=|V_ud|, we would obtain a deviation from the SMexpectations ranging from 1.5 to 3 \sigma, eventually signaling some NewPhysics beyond the SM.

Domaines: Physique des Hautes Energies - Phénoménologie [hep-ph]; Physique des Hautes Energies - Expérience [hep-ex]; Physique des Hautes Energies - Réseau [hep-lat]

Stéphan Narison. |V_{cd}|, |V_{cs}| and f_{D_s} from (semi) leptonic $D_{(s)}$-decays : signals of New Physics ?. Physics Letters B, 2008, 668 (4), pp.308-311. ⟨10.1016/j.physletb.2008.08.060⟩. ⟨hal-00378072⟩