arXiv subjects
Publications and source records attributed to M. Ahmady.
We report that the pion radius, decay constant, EM and transition form factors can simultaneously and accurately be predicted in light-front holographic QCD with a universal AdS/QCD mass scale, provided dynamical spin effects are taken into account.
We take into account dynamical spin effects in the holographic light-front pion wavefunction in order to predict the pion radius, decay constant, the pion electromagnetic and photon-to-pion transition form factors. We report a striking improvement in the description of all data.
We use QCD light-cone sum rules with holographic anti de Sitter/Chromodynamics (AdS/QCD) Distribution Amplitudes (DAs) for the $K^*$ meson in order to predict the full set of seven $B \to K^*$ transition form factors for intermediate-to-high recoil of the vector meson. We provide simple parametrizations for the form factors that fit our AdS/QCD predictions. We also provide parametrizations that fit both our AdS/QCD predictions and the most recent lattice data for low recoil. We use our form factors to predict the differential and total branching fraction of the rare dileptonic decay $B \to K^* μ^+ μ^-$ which we compare to the recent LHCb data.
We use QCD light-cone sum rules (LCSR) with holographic anti de Sitter/Chromodynamics (AdS/QCD) Distribution Amplitudes (DAs) for the $ρ$ meson to predict the form factors that govern the leading amplitudes of the rare radiative $B -> ργ$ decay and the semileptonic decay $B -> ρl ν$. We test the Isgur-Wise relation between the radiative and semileptonic form factors. We also compute the total width (in units of $|V_{ub}|^2$) for the semileptonic decay $B -> ρl ν$ as well as ratios of partial decay widths which are independent of $|V_{ub}|$.
We predict the isospin asymmetry as well as the branching ratio for the decay $B -> K* γ$ within QCD factorization using new anti-de Sitter/Quantum Chromodynamics (AdS/QCD) holographic Distribution Amplitudes (DAs) for the K* meson. Our prediction for the branching ratio agrees with that obtained using standard QCD Sum Rules (SR) DAs and with experiment. More interestingly, our prediction for the isospin asymmetry using the AdS/QCD DA does not suffer from the end-point divergence encountered when using the corresponding SR DA. We predict an isospin asymmetry of 3.3 % in agreement with the most recent average measured value of (5.2 \pm 2.6) % quoted by the Particle Data Group.
We derive holographic AdS/QCD Distribution Amplitudes for the transversely polarised $ρ$ meson and we use them to predict the branching ratio for the decays $\bar B^\circ\rightarrow ρ^\circ γ$ and $\bar B^\circ_s\rightarrow ρ^\circ γ$ beyond leading power accuracy in the heavy quark limit. For $\bar B^\circ\rightarrow ρ^\circ γ$, our predictions agree with those generated using Sum Rules (SR) Distribution Amplitudes and with the data from the BaBar and Belle collaborations. In computing the weak annihilation amplitude which is power-supressed in $\bar B^\circ\rightarrow ρ^\circ γ$ but is the leading contribution in $\bar{B}^{\circ}_s\rightarrow ρ^\circ γ$, we find that, in its present form, the AdS/QCD DA avoids the end-point divergences encountered with the SR DA .