# Semileptonic B decays into charmed D( **) mesons from Lattice QCD.

1 Laboratoire de Physique Corpusculaire (Aubière, Puy-de-Dôme)
LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand
Abstract : Semileptonic decays of $B$ mesons provide a rich source of knowledge for determining fundamental parameters of the Standard Model. This work reports mainly on the study of two semileptonic decay channels: the $B_s \to D_s \ell \bar\nu_\ell$ and $B\to D^{**} \ell \bar\nu_\ell$ (where the $D^{**}$ are the first orbitally excited states of the $D$ mesons having a positive parity). The theoretical framework is Lattice QCD which is considered as the only satisfying approach which calculates in a non perturbative way the transition amplitudes from first principles. By using the twisted mass QCD on the lattice with $N_f = 2$ dynamical flavors we studied, first, the spectroscopy of the scalar $D_0^*$ and the tensor $D_2^*$ states. Then, we determined the normalization $\mathscr G_s(1)$ of the form factor dominating $B_s \to D_s \ell \bar\nu_\ell$ in the Standard Model which provides a means of extracting the CKM matrix element $V_{cb}$. Next, we make the first lattice determination of $F_0(q^2)/F_+(q^2)$ and $F_T(q^2)/F_+(q^2)$ near the zero recoil. The obtained results are important for the discussion of this decay in various scenarios of physics beyond the Standard Model. Finally, we did a preliminary study of $B\to D^{**}$ where we have obtained a non vanishing matrix element corresponding to the decay of $B$ into the $D_0^*$ at zero recoil contrary to what was known in the heavy quark limit. Moreover, the computations corresponding to $B\to D_2^*$ show a signal indicating a difference with respect to the infinite mass limit prediction. These results are important to draw a firm conclusion on the ''1/2 vs 3/2 puzzle''
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Cited literature [134 references]

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Submitted on : Friday, February 7, 2014 - 1:49:46 PM
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• HAL Id : tel-00933976, version 2

### Citation

Mariam Atoui. Semileptonic B decays into charmed D( **) mesons from Lattice QCD.. High Energy Physics - Phenomenology [hep-ph]. Université Blaise Pascal - Clermont-Ferrand II, 2013. English. ⟨tel-00933976v2⟩

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