Probing new physics in B→Dℓ+ℓ−B \to D \ell^+ \ell^- decays by using angular asymmetries

We present the fully general, model independent study of a few rare semileptonic $B$ decays that get dominant contributions from $W$-annihilation and $W$-exchange diagrams, in particular $B^0 \to \bar{D}^0 \ell^+\ell^-$, where $\ell = e,\mu$. We consider the most general Lagrangian for the decay, and define three angular asymmetries in the Gottfried-Jackson frame, which are sensitive to new physics. We show how these angular asymmetries can be easily extracted from the distribution of events in the Dalitz plot for $B \to D \ell^+ \ell^-$ decays. Especially a non-zero forward-backward asymmetry within the frame would give the very first hint of possible new physics. These observations are also true for related decay modes, such as $B^+ \to D^+ \ell^+ \ell^-$ and $B^0 \to D^0 \ell^+ \ell^-$. Moreover, these asymmetry signatures are not affected by either $B^0$-$\bar{B}^0$ or $D^0$-$\bar{D}^0$ mixings. Then, this implies that both $B^0 \to \bar{D}^0 \ell^+ \ell^-$ and $B^0 \to D^0 \ell^+ \ell^-$ as well as their CP conjugate modes can all be considered together in our search for signature of new physics. Hence, it would be of great importance to look for and study these decays in the laboratory, LHCb and Belle II in particular.Comment: 5 pages, 2 figure

Probing the non-standard neutrino interactions using quantum statistics

Using the well established principles of Lorentz invariance, CP and CPT symmetry, and quantum statistics we do a model-independent study of effects of possible non-standard couplings of (Dirac and Majorana) neutrinos. The study is sensitive to the different quantum statistical properties of the Dirac and Majorana neutrinos which, contrary to neutrino-mediated processes of lepton number violation, could lead to observable effects not suppressed by the small ratios of neutrino and heavier particle masses. For processes with a neutrino-antineutrino pair of the same flavor in the final state, we formulate the ``Dirac Majorana confusion theorem (DMCT)'' showing why it is normally very difficult to observe the different behaviour of both kinds of neutrinos in experiments if they have only the standard model (SM)-like left-handed vector couplings to gauge bosons. We discuss deviations from the confusion theorem in the presence of non-standard neutrino interactions, allowing to discover or constrain such novel couplings. We illustrate the general results with two chosen examples of neutral current processes, $Z \to \nu \, \overline{\nu}$ and $\mathcal{P}_i \to \mathcal{P}_f \, \nu \, \overline{\nu}$ (with $\mathcal{P}_{i,f}$ denoting pseudoscalar mesons, such as $B,K,\pi$). Our analysis shows that using 3-body decays the presence of non-standard interactions can not only be constrained but one can also distinguish between Dirac and Majorana neutrino possibilities.Comment: 15 pages, 6 figures, for the published version visit the DO