Helicity amplitudes in $B \to D^{*} \bar{\nu} l$ decay

Understand

We use a recent formalism of the weak hadronic reactions that maps the transition matrix elements at the quark level into hadronic matrix elements, evaluated with an elaborate angular momentum algebra that allows finally to write the weak matrix elements in terms of easy analytical formulas.

• In particular they appear explicitly for the different spin third components of the vector mesons involved.
• We extend the formalism to a general case, with the operator $\gamma^\mu -\alpha\gamma^\mu \gamma_5$, that can accommodate different models beyond the standard model and study in detail the $B \to D^{*} \bar{\nu} l$ reaction for the different helicities of the $D^*$.
• The results are shown for each amplitude in terms of the $\alpha$ parameter that is different for each model.