arXiv subjects
Publications and source records attributed to Ruben Sandapen.
Using light-front holography, we predict simultaneously the pion decay constant and the pion charge radius by taking into account (higher twist) dynamical spin effects whose relative importance is constrained by QCD.
We report that the inclusion of dynamical spin effects in the pion holographic light-front wavefunction leads to a remarkable improvement in describing pion observables (pion mean charge radius, decay constant, spacelike electromagnetic form factor) without the need to invoke higher Fock state contributions and/or a special AdS/QCD mass scale for the pion.
We account for dynamical spin effects in the holographic light-front wavefunction of the pion in order to predict its mean charge radius, decay constant, spacelike electromagnetic form factor, twist-2 Distribution Amplitude and the photon-to-pion transition form factor. Using a universal fundamental AdS/QCD scale of 523 MeV and a constituent quark mass of 330 MeV, we find a remarkable improvement in describing all observables.
We compute the rate for diffractive $ϕ$ electro-production using the Color Glass Condensate dipole model. The model parameters are obtained from fits to the most recent combined HERA data on inclusive deep inelastic scattering. As for the $ϕ$ meson, we use an AdS/QCD holographic light front wavefunction. Our predictions are compared to the available data collected at the HERA collider.
We use an anti-de Sitter/Quantum Chromodynamics (AdS/QCD) holographic light-front wavefunction for the $ρ$ and $ϕ$ mesons, in conjunction with the Color Glass Condensate (CGC) dipole cross-section whose parameters are fitted to the most recent 2015 high precision HERA data on inclusive Deep Inelastic Scattering (DIS), in order to predict the cross-sections for diffractive $ρ$ and $ϕ$ electroproduction. Our results suggest that the holographic meson light-front wavefunction is able to give a simultaneous description of the $ρ$ and $ϕ$ production data provided we use a set of light quark masses with $m_{u,d}$ < $m_{s}$ ~ 0.14 GeV.
We predict the cross-section for diffractive $ϕ$ electroproduction within the dipole model, using a holographic meson wavefunction for the $ϕ$. For the dipole cross-section, we use the Color Glass Condensate dipole model whose parameters are fitted to the latest 2015 combined HERA data on Deep Inelastic Scattering. Choosing a strange quark mass of $0.14$ GeV, we find good agreement with the available data.
We compute the branching ratio and forward-backward asymmetry ($A_{FB}$) distribution for the rare dileptonic decay $B \to K^* μ^+ μ^-$ for the full range of $q^2$, the dimuon mass squared, region. For the required form factors, we use nonperturbative inputs as predicted by the anti-de Sitter (AdS)/QCD correspondence. When using the Breit-Wigner model with momentum-dependent decay constants to account for the $ψ$ and $ψ^\prime$ resonance effects in the nonresonance region of the spectrum, we find our predictions to be in better agreement with the experimental data for the branching ratio.
We build on the success of AdS/QCD in predicting diffractive $ρ$ meson production to obtain the transition form factors for B decays to light mesons. Consequently, we predict several observables associated with $B\to ρ\ellν$ semileptonic and $B\to K^*μ^+μ^-$ dileptonic decays. Our predictions are compared to the available experimental data.
The light front wavefunction obtained from anti-de Sitter Quantum Chromodynamics is used to calculate the light cone distribution amplitudes for $ρ$ and $K^*$ vector mesons. These distribution amplitudes are then utilized to calculate the $B \to ρ,\; K^*$ transition form factors via light cone sum rules. Two-parameter fits of our results for low to intermediate momentum transfer $q^2$ that includes the QCD lattice data at high $q^2$ are presented. Consequently, we give predictions for the semileptoic $B \to ρ\ell ν$ and dileptonic $B \to K^* μ^+ μ^-$ decays.
We use the AdS/QCD distribution amplitudes for light mesons to calculate the transition form factors for B to $ρ$, $K^*$ decays. These form factors are then utilized to make predictions for the semileptonic $B\toρ\ellν$ and dileptonic $B\to K^* μ^+μ^-$ decays. We compare our predictions to the experimental data from BaBar and LHCb.
Light front Holography is a formalism developed by Brodsky and de Téramond in which analytic forms for the hadronic bound state wavefunctions can be obtained. We have used the holographic light front wavefunctions thus obtained in order to calculate the distribution amplitudes of the light vector mesons $ρ$ and $K^*$. As a result, we are able to calculate the form factors for $B\to ρ, K^*$ transitions as well as $Λ_{\rm QCD}/m_b$ contributions in radiative $B_{(s)}\to (ρ,K^*)γ$ decays. We compare our predictions to the available experimental data.
We use AdS/QCD holographic Distributions Amplitudes for the vector mesons $ρ$ and $K^*$ in order to predict the radiative decays $B \to ργ$ and $B \to K^* γ$ as well as the semileptonic decays $B \to ρl ν$ and $B \to K^* μ^+ μ^-$. For the radiative decays, we find that the AdS/QCD DAs offer the advantage of avoiding end-point singularities when computing power suppressed contributions. For the semileptonic decays $B \to ρl ν$ and $B \to K^* μ^+ μ^-$, we compare our predictions to the latest BaBar and LHCb data respectively.
We predict observables in radiative B decays to vector mesons using holographic AdS/QCD Distribution Amplitudes for the vector mesons. We find that end-point divergences can be avoided when computing power-suppressed contributions in the heavy quark limit. The results reported here can be found in references [1] and [2].
We demonstrate another success of the AdS/QCD correspondence by showing that an AdS/QCD holographic light-front wavefunction for the $ρ$ meson generates predictions for the cross-sections of diffractive $ρ$ production that are in agreement with data collected at the HERA electron-proton collider.