Ruben Sandapen, Mohammad Ahmady
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].
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We predict the $\mathcal{V} \to \mathcal{P} γ$ decay widths and the $\mathcal{V} \to \mathcal{P} γ^{*}$ transition form factors, where $\mathcal{V}=(ρ, ω, K^*, ϕ)$ and $\mathcal{P}= (π,K, η,η^\prime)$, using spin-improved holographic light-front wavefunctions for the mesons. We find excellent agreement with the available data for both the decay widths and the timelike transition form factors extracted from the leptonic conversion decays $\mathcal{V} \to \mathcal{P} l^+ l^-$.
We predict the twist-2 Transverse Momentum Dependent parton distribution functions (TMDs) of the pion, namely the unpolarized quark TMD, $f_{1}(x, k_\perp)$, and the transversely polarized quark TMD, also known as the Boer-Mulders function, $h^\perp_{1}(x, k_\perp)$, using a holographic light-front pion wavefunction with dynamical spin effects. These spin effects, in conjunction with gluon rescattering, are crucial to predict a non-zero holographic Boer-Mulders function. We investigate the use of a non-perturbative SU(3) gluon rescattering kernel, thus going beyond the usual approximation of p…
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…
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 l…
Holographic quark masses and radiative decays of heavy vector mesons
本文利用全息QCD模型与非相对论Segre公式，推导出重矢量介子的组分夸克质量及多种辐射衰变宽度，并与实验对比，开辟了AdS/QCD中介子谱学新范式。
Predicting $\sin(2ϕ-ϕ_{s})$ azimuthal asymmetry in pion-proton induced Drell-Yan process using holographic light-front QCD
本研究在横动量依赖因子化框架下，结合全息光前π介子波函数与软墙AdS/QCD构建的质子TMD模型，计算Drell-Yan过程的方位角不对称性，探究非微扰SU(3)胶子再散射的作用，为研究非微扰QCD效应提供工具并指导实验。
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 $|V_{ub}|$.
The application of light front holographic QCD to B physics
本研究利用Brodsky和de Téramond发展的光前全息方法得到的强子波函数，计算轻矢量介子分布振幅，进而得到B介子跃迁形状因子及辐射衰变的相关贡献，并与实验数据对比。
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^*…
Within the bottom-up holographic approach to QCD, the highly excited hadrons are identified with the bulk normal modes in the fifth "holographic" dimension. We show that additional states in the same mass range can appear also from taking into consideration the 5D fields dual to higher dimensional QCD operators. The possible effects of these operators were not taken into account in almost all phenomenological applications. Using the scalar case as the simplest example, we demonstrate that the additional higher dimensional operators lead to a large degeneracy of highly excited states in the Sof…
We use QCD sum-rules to study the decays $ϕ\to ηγ$ and $ϕ\to η^\prime γ$, obtaining ${\cal B}(ϕ\to ηγ)=(1.15 \pm 0.2) 10^{-2}$ and ${\cal B}(ϕ\to η^\prime γ)=(1.18 \pm 0.4) 10^{-4}$, in very good agreement with existing experimental data. We also discuss the issue of $η-η^\prime$ mixing, predicting the $η$ and $η^\prime$ decay constants in a mixing scheme in the quark-flavour basis.
We quantify the importance of dynamical spin effects in the holographic light-front wavefunctions of the pion, kaon, $η$ and $η^\prime$. Using a universal AdS/QCD scale and constituent quark masses, we find that such effects are maximal in the pion where they lead to an excellent simultaneous description of a wide range of data: the decay constant, charge radius, spacelike EM and transition form factors, as well as, after QCD evolution, both the parton distribution function and the parton distribution amplitude data from Fermilab. These dynamical spin effects lead up to a $30\%$ chance of find…
High-precise determination of critical exponents in holographic QCD
本研究在全息QCD模型中高精度计算临界终点位置，用极限方法分析临界指数趋近行为，发现线性拟合仅适用于近临界终点区域，不同方向趋近的临界指数最终收敛，为临界现象研究提供基准。
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 revisit the $U(1)_A$ anomaly in the holographic model of low-energy QCD by Witten, Sakai, and Sugimoto, presenting a new and direct derivation of the Witten-Veneziano mechanism for generating the mass of the $η'$ through an anomalous mixing of the Ramond-Ramond $C_1$ field with the singlet component of the pseudoscalar mesons. The latter turns out to have a kinetic mixing with the normalizable modes of the $C_1$ field representing pseudoscalar glueballs, yielding additional vertices for their production and their decay that dominate over those of the unmixed case considered previously in th…
The drag force of charm quarks propagating through a thermalized system of Quark Gluon Plasma (QGP) has been considered within the framework of both conformal/non-conformal Anti de Sitter (AdS) correspondence. Newly derived Einstein Fluctuation-Dissipation relation has been used to calculate the heavy flavor diffusion coefficients. Using the drag and diffusion coefficients as inputs Langevin equation has been solved to study the heavy flavor suppression factor. It has been shown that within conformal AdS correspondence the D-meson suppression at LHC energy can be reproduced where as the non-co…
Chiral Separation Effect from Holographic QCD
本文利用规范/引力对偶性分析QCD中的手性分离效应，通过拟合QCD数据的V-QCD全息模型研究CSE电导率对温度和密度的依赖性，发现其结果与格点QCD模拟定性一致，并预测了有限化学势下的行为。
Given a resonance of known mass, width, and J^{PC}, we can determine its gluonic branching fraction, b(R->gg), from data on its production in radiative vector quarkonium decay, V -> gamma+R. For most resonances b(R->gg) is found to be O(10%), consistent with being q-qbar states, but we find that both pseudoscalars observed in the 1440 MeV region have b(R->gg) ~ 1/2 - 1, and b(f_0^{++}->gg) ~ 1/2. As data improves, b(R->gg) should be a useful discriminator between q-qbar and gluonic states and may permit quantitative determination of the extent to which a particular resonance is a mixture of gl…
We study quantum fields on an arbitrary, rigid background with boundary. We derive the action for a scalar in the holographic basis that separates the boundary and bulk degrees of freedom. A relation between Dirichlet and Neumann propagators valid for any background is obtained from this holographic action. As a simple application, we derive an exact formula for the flux of bulk modes emitted from the boundary in a warped background. We also derive a formula for the Casimir pressure on a $(d-1)$-brane depending only on the boundary-to-bulk propagators, and apply it in AdS. Turning on couplings…
Radiative Meson and Glueball Decays in the Witten-Sakai-Sugimoto Model
在有限夸克质量的Witten-Sakai-Sugimoto全息模型中计算介子与胶球辐射衰变率，发现胶球二光子宽度可观，支持$f_0(1710)$的胶球解释，并指出涉及胶球交换的强子光散射对μ子g-2贡献极小。
The leading-twist distribution amplitude for the longitudinal rho-meson was studied using QCD Sum Rules with nonlocal condensates and a spectral density which includes next-to-leading order radiative corrections. The obtained profile is compared with results from standard QCD sum rules, lattice QCD, holographic QCD, a light-front quark model, and the instanton liquid model. Preliminary estimates for the first two moments of the transverse $ρ$-meson distribute amplitude are also given.
Tensor meson couplings in AdS/QCD
本文在AdS/QCD硬壁和软壁模型中计算f2(1270)介子的强子和辐射耦合，并与色散关系及振幅方法结果对比，验证了全息描述自旋-2介子的可靠性。
We present calculations of radiative transitions between vector and pseudoscalar quarkonia in the light-front Hamiltonian approach. The valence sector light-front wavefunctions of heavy quarkonia are obtained from the Basis Light-Front Quantization (BLFQ) approach in a holographic basis. We study the transition form factor with both the traditional "good current" $J^+$ and the transverse current $\vec J_\perp$ (in particular, $J^R=J^x+i J^y$). This allows us to investigate the role of rotational symmetry by considering vector mesons with different magnetic projections ($m_j=0,\pm 1$). We use t…
Radiative transitions between charmonium states offer an insight into the internal structure of heavy-quark bound states within QCD. We compute, for the first time within lattice QCD, the transition form-factors of various multipolarities between the lightest few charmonium states. In addition, we compute the experimentally unobservable, but physically interesting vector form-factors of the $η_c, J/ψ$ and $χ_{c0}$. To this end we apply an ambitious combination of lattice techniques, computing three-point functions with heavy domain wall fermions on an anisotropic lattice within the quenched ap…
In this paper, I study final state QCD radiative corrections to off-shell single top production via decaying $W$ at hadron collider energies. The tree level Breit-Wigner distribution of the produced top invariant mass is distorted by final state QCD radiation, while the peak position remains unchanged. The exact one loop QCD calculation and the narrow width approximation agree in predicting the cross section, the hadronic transverse energy distribution and the bottom-lepton invariant mass distribution.
It is proved that symmetry structure of the parity-viol. (p.v.) amplitudes of weak radiative hyperon decays in the VMD approach, and the violation of Hara's theorem in particular, are also obtained when direct coupling e_q \bar{q}γ_μq A^μ of photon to quarks is used in place of VMD. Thus, violation of Hara's theorem in VMD-based models does not result from the lack of gauge invariance. It is further shown that, in the static limit of the quark model, the CA commutator term in the p.v. amplitudes of nonleptonic hyperon decays (NLHD) and the parity-violating Σ^+ \to p γdecay amplitude are propor…
Linear Dilaton in Cosmology and Particle Physics
本综述研究由参数ν描述的5D背景，其在ν=0时对应AdS、ν=1时对应线性伸缩子，探讨线性伸缩子在粒子物理与膜世界宇宙学中的应用，指出相关带隙连续谱、暗物质候选体等结果。
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