Leptoquark effects on b→sννˉb \to s \nu \bar{\nu} and B→Kl+l−B \to K l^+ l^- decay processes

We study the rare semileptonic decays of $B$ mesons induced by $b \to s \nu \bar{\nu}$ as well as $b \to s l^+ l^-$ transitions in the scalar leptoquark model where the leptoquarks transform as $(3,2,7/6)$ and $(3,2,1/6)$ under the standard model gauge group. The leptoquark parameter space is constrained using the most recent experimental results on ${\rm Br}(B_s \rightarrow \mu^+ \mu^-)$ and ${\rm Br}(B_d \to X_s \mu^+ \mu^-)$ processes. Considering only the baryon number conserving leptoquark interactions, we estimate the branching ratios for the exclusive $\bar{B} \rightarrow \bar{K}^{(*)} \nu \bar{\nu}$ and inclusive $B \rightarrow X_s \nu \bar{\nu}$ decay processes by using the constraint parameters. We also obtain the low recoil (large lepton invariant mass, i.e., $q^2 \sim m^2_b$) predictions for the angular distribution of $\bar B \rightarrow \bar{K} l^+ l^-$ process and several other observables including the flat term and lepton flavour non-universality factor in this model.Comment: 24 pages, 10 figures, version to appear in New J. Phy

New Physics effects in charm meson decays involving c→ul+l−(li∓lj±)c \to u l^+ l^- (l_i^\mp l_j^\pm) transitions

We study the effect of scalar leptoquark and $Z^\prime$ boson on the rare decays of $D$ mesons involving flavour changing transitions $c \to u l^+ l^- (l^\mp_i l^\pm_j)$. We constrain the new physics parameter space using the branching ratio of the rare decay mode $D^0 \to \mu^+ \mu^-$ and the $D^0-\bar D^0$ oscillation data. We compute the branching ratios, forward-backward asymmetry parameters and flat terms in $D^{+(0)} \to \pi^{+(0)} \mu^+ \mu^-$ processes using the constrained parameters. The branching ratios of the lepton flavour violating $D$ meson decays, such as $D^0 \to \mu e, ~\tau e$ and $D^{+(0)} \to \pi^{+(0)} \mu^- e^+$ are also investigated.Comment: 30 pages, 8 figures, to appear in EPJ