Analyse du canal $B^0 _s \to J/\psi {\overline{k}}^{*0}$ et contraintes sur les processus pingouins dans les désintégrations $B^0 _s \to J/\psi\phi$ auprès du détecteur LHCb

Within the Standard Model, the decay $B^0_s\to J/\psi \phi$, can occur via two main processes: the predominant tree and the sub-leading penguin. Penguin contributions have been so far ignored. Controlling them is crucial in order to disentangle Standard Model effects from possible New Physics in the measurement of $\phi_s$. We studied the $B^0_s\to J / \psi