We revisit QCD calculations of radiative heavy meson decay form factors by including the subleading power corrections from the twist-two photon distribution amplitude at next-to-leading-order in $α_s$ with the method of the light-cone sum rules (LCSR). The desired hard-collinear factorization formula for the vacuum-to-photon correlation function with the interpolating currents for two heavy mesons is constructed with the operator-product-expansion technique in the presence of evanescent operators. Applying the background field approach, the higher twist corrections from both the two-particle and three-particle photon distribution amplitudes are further computed in the LCSR framework at leading-order in QCD, up to the twist-four accuracy. Combining the leading power "point-like" photon contribution at tree level and the subleading power resolved photon corrections from the newly derived LCSR, we update theory predictions for the nonperturbative couplings describing the electromagnetic decay processes of the heavy mesons $H^{\ast \, \pm} \to H^{\pm} \, γ$, $H^{\ast \, 0} \to H^{0} \, γ$, $H_s^{\ast \, \pm} \to H_s^{\pm} \, γ$ (with $H=D, \, B$). Furthermore, we perform an exploratory comparisons of our sum rule computations of the heavy-meson magnetic couplings with the previous determinations based upon different QCD approaches and phenomenological models.
Applying the method of light-cone sum rules with photon distribution amplitudes, we compute the subleading-power correction to the radiative leptonic $B \to γ\ell ν$ decay, at next-to-leading order in QCD for the twist-two contribution and at leading order in $α_s$ for the higher-twist contributions, induced by the hadronic component of the collinear photon. The leading-twist hadronic photon effect turns out to preserve the symmetry relation between the two $B \to γ$ form factors due to the helicity conservation, however, the higher-twist hadronic photon corrections can yield symmetry-breaking…
Employing the systematic framework of soft-collinear effective theory (SCET) we perform an improved calculation of the leading-power contributions to the double radiative $B_{d, \, s}$-meson decay amplitudes in the heavy quark expansion. We then construct the QCD factorization formulae for the subleading power contributions arising from the energetic photon radiation off the constituent light-flavour quark of the bottom meson at tree level. Furthermore, we explore the factorization properties of the subleading power correction from the effective SCET current $J^{(A2)}$ at ${\cal O} (α_s^0)$. T…
I discuss the two-particle subleading power corrections in radiative leptonic $B \to γ\ell ν$ decay at next-to-leading order in $α_s$ with the dispersion approach. Employing the method of regions, factorization of the $B \to γ^{\ast}$ form factors is demonstrated explicitly, at one loop, for a space-like hard-collinear photon. The two-particle soft (end-point) contribution is shown to be suppressed by one power of $Λ/m_b$, in the heavy quark limit, compared with the leading power contribution computed from QCD factorization. I further report the recent calculation on the three-particle sublead…
We reconsider the QCD predictions for the radiative decay $B\to γ\ell ν_\ell$ with an energetic photon in the final state by taking into account the $1/E_γ, 1/m_b$ power-suppressed hard-collinear and soft corrections from higher-twist $B$-meson light-cone distribution amplitudes (LCDAs). The soft contribution is estimated through a dispersion relation and light-cone QCD sum rules. The analysis of theoretical uncertainties and the dependence of the decay form factors on the leading-twist LCDA $ϕ_+(ω)$ shows that the latter dominates. The radiative leptonic decay is therefore well suited to cons…
The study of amplitudes and cross sections in the soft and collinear limits allows for an understanding of their all orders behavior, and the identification of universal structures. At leading power soft emissions are eikonal, and described by Wilson lines. Beyond leading power the eikonal approximation breaks down, soft fermions must be added, and soft radiation resolves the nature of the energetic partons from which they were emitted. For both subleading power soft gluon and quark emissions, we use the soft collinear effective theory (SCET) to derive an all orders gauge invariant bare factor…
We consider the subleading contributions of the hadronic vacuum polarization, involving the $π^0γ^*γ^*$ transition form factor, to the muon anomalous magnetic moment $g-2$. Various models for the form factor, based on hadronic ansatzes and holographic principles, are considered: They are the Wess-Zumino-Witten, vector meson dominance, lowest meson dominance (one and two vector resonances) models, and AdS/QCD. The model parameters are determined by fitting the experimental data for the $e^+ e^- \rightarrow π^0 γ$ total cross section. We report numerical results of the corrections to the muon $g…
Using methods developed for hard exclusive QCD processes, we calculate the asymptotic behaviour of heavy-meson form factors at large recoil. It is determined by the leading- and subleading-twist meson wave functions. For $1\ll |v\cdot v'|\ll m_Q/Λ$, the form factors are dominated by the Isgur--Wise function, which is determined by the interference between the wave functions of leading and subleading twist. At $|v\cdot v'|\gg m_Q/Λ$, they are dominated by two functions arising at order $1/m_Q$ in the heavy-quark expansion, which are determined by the leading-twist wave function alone. The sum o…
We study the subleading corrections originating from the 3-parton (q\bar q g) Fock states of final-state mesons in B decays. The corrections could give significant contributions to decays involving an ωor η^{(\prime)} in the final states. Our results indicate the similarity of ωK and ωπ^- rates, of order 5\times 10^{-6}, consistent with the recent measurements. We obtain a_2(B\to J/ψK)\approx 0.27+0.05i, in good agreement with data. Without resorting to the unknown singlet annihilation effects, 3-parton Fock state contributions can enhance the branching ratios of Kη' to the level above 50\time…
We construct the effective chiral Lagrangian involving the D--mesons and Goldstone bosons at next-to-leading order taking into account strong as well as electromagnetic interactions. This allows us to disentangle -- to leading order in isospin violation -- the electromagnetic and the strong contribution to the D--meson mass differences. In addition, we also apply the interaction to the decay D_{s0}^*(2317)-> D_s pi0 under the assumption that the D_{s0}^*(2317) is a hadronic molecule. We find (180+-110) keV for the decay width $Γ(D_{s0}^*(2317)-> D_s pi0) -- consistent with currently existing e…
The leptonic radiative decay $B \to γlν$ is of great importance in the determination of $B$ meson wave functions, and evaluating the form factors $ F_{V,A}$ are the essential problem on the study of this channel. We computed next-to-leading power corrections to the form factors within the framework of PQCD approach, including the power suppressed hard kernel, the contribution from a complete set of three-particle $B$ meson wave functions up to twist-4 and two-particle off light-cone wave functions, the $1/m_b$ corrections in heavy quark effective theory, and the contribution from hadronic stru…
We elaborate on the radiative behaviour of tree-level scattering amplitudes in the soft regime. We show that the sub-leading soft term in single-gluon emission of quark-gluon amplitudes in QCD is controlled by differential operators, whose universal form can be derived from both on-shell recursion relation and gauge invariance, as it was shown to hold for graviton- and gluon-scattering.
We consider the non-relativistic limit of the QCD Hamiltonian in the Coulomb gauge, to describe radiative transitions between conventional charmonium states and from the lowest multiplet of $c\bar{c}$ hybrids to charmonium mesons. The results are compared to potential quark models and lattices calculations.
We consider a collinear effective theory of highly energetic quarks with energy E, interacting with collinear and soft gluons by integrating out collinear degrees of freedom to subleading order. The collinear effective theory offers a systematic expansion in power series of a small parameter lambda ~ p_{\perp}/E, where p_{\perp} is the transverse momentum of a collinear particle. We construct the effective Lagrangian to first order in $λ$, and discuss its features including additional symmetries such as collinear gauge invariance and reparameterization invariance. Heavy-light currents can be m…
We perform an $\textit{ab initio}$ calculation of the $N_c$ scaling of the low-energy couplings of the chiral Lagrangian of low-energy strong interactions, extracted from the mass dependence of meson masses and decay constants. We compute these observables on the lattice with four degenerate fermions, $N_f=4$, and varying number of colours, $N_c=3-6$, at a lattice spacing of $a\simeq 0.075$ fm. We find good agreement with the expected $N_c$ scaling and measure the coefficients of the leading and subleading terms in the large $N_c$ expansion. From the subleading $N_c$ corrections, we can also i…
We construct the higher twist structure functions that describe inclusive b hadron decays in regions of phase space where the hadronic decay products carry high energy but have low invariant mass. We show that, for B meson decays, there are four new non-vanishing matrix elements of non-local operators. We show that to subleading twist these decays are parametrized in terms of four functions. We compute the tree-level matching for a general heavy-to-light current and apply it to B -> X_s gamma. Using a simple model for these functions we estimate the subleading twist contributions to this decay…
Radiative magnetic dipole decays of heavy-light vector mesons into pseudoscalar mesons V -> Pγare considered within the relativistic quark model. The light quark is treated completely relativistically, while for the heavy quark the 1/m_Q expansion is used. It is found that relativistic effects result in a significant reduction of decay rates. Comparison with previous predictions and recent experimental data is presented.
The exclusive rare radiative B meson decays to orbitally excited axial-vector mesons K_1^*(1270), K_1(1400) and to the tensor meson K_2^*(1430) are investigated in the framework of the relativistic quark model based on the quasipotential approach in quantum field theory. These decays are considered without employing the heavy quark expansion for the s quark. Instead the s quark is treated to be light and the expansion in inverse powers of the large recoil momentum of the final K^{**} meson is used to simplify calculations. It is found that the ratio of the branching fractions of rare radiative…
We show in a model independent way the equality of the branching fractions and strong phases for B-> D_1M and B-> D_2^*M at leading order in Lambda _{QCD}/Q and alpha_s(Q) where Q={m_b,m_c,E_M} and M is a light meson. These results apply in the color allowed and color suppressed channels and follow from a factorization theorem in SCET combined with heavy quark symmetry. The expected heavy quark symmetry suppression of leading order contributions in the color allowed sector based on analysis of semileptonic decays, is shown to disappear at maximum recoil. Subleading corrections are suppressed b…
The decay $B\to f_0(980)K is studied within the framework of QCD factorization and the two-quark scenario for $f_0(980)$. There are two distinct penguin contributions and their interference depends on the unknown mixing angle $θ$ of strange and nonstrange quark contents of $f_0(980)$: destructive for $0<θ<π/2$ and constructive for $π/2<θ<π$. The QCD sum rule method is applied to evaluate the leading-twist light-cone distribution amplitudes and the scalar decay constant of $f_0$. We conclude that the short-distance approach is not adequate to explain the observed large rates of $f_0K^-$ and $f_…
The exclusive rare radiative B meson decay to the orbitally excited tensor K_2^*(1430) meson is investigated in the framework of the relativistic quark model based on the quasipotential approach in quantum field theory. The calculated branching ratio BR(B --> K_2^*(1430)γ)=(1.7\pm 0.6)\times 10^{-5} as well as the ratio BR(B --> K_2^*(1430)γ)/BR(B --> K^*(892)γ)=0.38\pm 0.08 is found in a good agreement with recent experimental data from CLEO.
The use of the BFKL kernel improved by the inclusion of subleading terms generated by renormalization group (RG) analysis has been suggested to cure the instabilities in the behavior of the BFKL Green's function in the next-to-leading approximation (NLA). We test the performance of a RG-improved kernel in the determination of the amplitude of a physical process, the electroproduction of two light vector mesons, in the BFKL approach in the NLA. We find that a smooth behavior of the amplitude with the center-of-mass energy can be achieved, setting the renormalization and energy scales appearing …
The contributions of subleading shape functions to inclusive decay distributions of B mesons are derived from a systematic two-step matching of QCD current correlators onto soft-collinear and heavy-quark effective theory. At tree-level, the results can be expressed in terms of forward matrix elements of bi-local light-cone operators. Four-quark operators, which arise at O(g^2), are included. Their effects can be absorbed entirely into a redefinition of other shape functions. Our results are in disagreement with some previous studies of subleading shape-function effects in the literature. A num…
We consider meson radiative decays within the framework of $U_0(1)\times U(1)\times SU(2)$ gauge symmetry. This approach is based on the linear sigma-model extended by the gauge and quark-meson interactions. Physical content and parameters of the model are discussed. Theoretical predictions for some radiative decays of vector mesons are in a good agreement with the experimental data.
The huge datasets collected at the two B factories, Belle and BaBar, have made it possible to explore the radiative penguin process b --> s gamma, the electroweak penguin process b --> s l+ l- and the suppressed radiative process b --> d gamma in detail, all in exclusive channels and inclusive measurements. Theoretical tools have also advanced to meet or surpass the experimental precision, especially in inclusive calculations and the various ratios of exclusive channels. In this article, we review the theoretical and experimental progress over the past decade in the radiative and electroweak p…
We discuss the most general form of the leading power suppressed collinear operators in the soft-collinear effective theory. Such operators appear in the description of power corrections to exclusive heavy flavor decays into energetic light hadrons. Reparametrization invariance in the SCET provides powerful constraints on the Wilson coefficients of the subleading collinear operators. We present explicit results for the matrix elements of these operators on pseudoscalar and vector mesons, which are expressed in terms of twist-2 and twist-3 light-cone wave functions. We consistently include the …
Considering four-point correlation functions of color-singlet quark bilinears, we investigate, in the large-$N_{\mathrm{c}}$ limit of QCD, the subleading diagrams that involve, in the $s$-channel of meson-meson scattering amplitudes, two-quark--two-antiquark intermediate states. The latter contribute, together with gluon exchanges, to the formation, at the hadronic level, of two-meson and tetraquark intermediate states. It is shown that the two-meson contributions, which are predictable, in general, from leading-order $N_{\mathrm{c}}$-behaviors, consistently satisfy the constraints resulting f…
We evaluate the radiative and hadronic decay rates of the $D^*$ mesons using the Heavy Quark Effective Theory and the Vector Meson Dominance hypothesis. We also estimate the width of the $B^*$ electromagnetic transitions and the radiative decays of positive parity $J^P=0^+, 1^+$ charmed mesons.
We systematically compute and discuss meson and muon polarized radiative decays. Doubly differential distributions in terms of momenta and helicities of the final lepton and photon are explicitly computed. The undergoing dynamics giving rise to lepton and photon polarizations is examined and analyzed in the soft and hard region of momenta. The particular configurations made by right-handed leptons with accompanying photons are investigated and interpreted as a manifestation of the axial anomaly. The photon polarization asymmetry is evaluated. Finiteness of polarized amplitudes against infrared…
We study the radiative $ρ^0\to π^+π^-γ$ and $ρ^0\to π^0π^0γ$ decays and we calculate their branching ratios using a phenomenological approach by adding to the amplitude calculated within the framework of chiral perturbation theory and vector meson dominance the amplitude of $σ$-meson intermediate state. Our results for the branching ratios are in good agreement with the experimental values.
QED radiative effects are considered in the case of measurement of spin-density matrix elements of diffractive $ρ$-meson electroproduction. Large radiative correction for $r^5_{00}$ is found in the kinematics of collider experiments at HERA.
In this paper, we study the rare radiative processes $B_c\to D_{sJ} ^{(*)}γ$ within the Standard Model, where $D_{sJ}^{(*)}$ stands for the meson $D_s^*$,~$D_{s1}(2460,2536)$ or ~$D_{s2}^*(2573)$. During the investigations, we consider the contributions from the penguin, annihilation, color-suppressed and color-favored cascade diagrams. Our results show that: 1) the penguin and annihilation contributions are dominant in the branching fractions; 2) for the processes $B_c\to D_s^{*}γ$ and $B_c\to D_{s1}(2460,2536)γ$, the effects from the color-suppressed and color-favored cascade diagrams are un…
In the framework of the local Nambu-Jona-Lasinio model the radiative decay widths of the scalar mesons $f_0(980)$ and $a_0(980)$ into $ργ$ and $ωγ$ are calculated. The contributions of the quark loops and the meson loops are taken into account. For the radiative decays of the scalar meson $f_0(980)$ the contribution of the meson loops plays the dominant role. On the other side for the radiative decays of the scalar meson $a_0(980)$ the main contribution is given by the quark loops.
To analyze an electromagnetic and strong hadron processes at low energies, we consider the renormalizable model with the U0(1) x U(1) x SU(2) gauge symmetry. This approach is based on the linear sigma-model extended by the gauge and quark-meson interactions. Physical content and parameters of the model are discussed. Theoretical predictions for some radiative decays of vector mesons are in a good agreement with the experimental data.
We evaluate the radiative decay into a pseudoscalar meson and a photon of the whole set of the axial-vector mesons dynamically generated from the vector-pseudoscalar meson ($VP$) interaction. We take into account tree level and loop diagrams coming from the axial-vector decay into a vector and a pseudoscalar meson. We find a large span for the values of the radiative widths of the different axial-vector mesons. In particular, we evaluate the radiative decay into $K γ$ of the two $K_1(1270)$ states, recently claimed theoretically, and discuss the experimental values quoted so far on the assumpt…
What can we learn from the radiative decays of the $D_{s1}(2460)$ meson?
Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；Institute for Advanced Simulation, Forschungszentrum Jülich（于利希研究中心先进模拟研究所）；Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn（波恩大学亥姆霍兹射线与核物理研究所）
Exclusive semileptonic B decays to radially excited charmed mesons are investigated at the first order of the heavy quark expansion. The arising leading and subleading Isgur-Wise functions are calculated in the framework of the relativistic quark model. It is found that the 1/m_Q corrections play an important role and substantially modify results. An interesting interplay between different corrections is found. As a result the branching ratio for the B-> D'eνdecay is essentially increased by 1/m_Q corrections, while the one for B-> D*'eνis only slightly influenced by them.
The contribution of subleading jet functions to inclusive decay distributions of $B$ mesons are derived from a systematic two-step matching of QCD current correlators onto soft collinear and heavy quark effective theory. Focusing on the tree level matching of QCD onto soft collinear effective theory, the subleading jet functions are defined to all orders in $α_s(μ_i)$ (with $μ_i^2\sim m_bΛ_{\rm QCD}$) and are calculated explicitly at first order in $α_s(μ_i)$. We present explicit expressions for the decay rates of $B\to X_u l \barν$ and the $Q_{7γ}-Q_{7γ}$ contribution to $B\to X_s γ$, where t…
We study the effect of scalar-isoscalar $f_{0}(980)$ meson in the mechanism of the radiative $ϕ\to π^{+}π^{-}γ$ decay. A phenomenological approach is used to study this decay by considering the contributions of $σ$-meson, $ρ$-meson and $f_{0}(980)$-meson. The interference effects between different contributions are analyzed and the branching ratio for this decay is calculated. We observe that $f_0$ meson contribution is much larger than the contributions of the other terms.
We explore the use of optimized operators, designed to interpolate only a single meson eigenstate, in three-point correlation functions with a vector-current insertion. These operators are constructed as linear combinations in a large basis of meson interpolating fields using a variational analysis of matrices of two-point correlation functions. After performing such a determination at both zero and non-zero momentum, we compute three-point functions and are able to study radiative transition matrix elements featuring excited state mesons. The required two- and three-point correlation function…
We present a QCD sum rule calculation of the Isgur-Wise form-factor tau_1(v.v') and tau_2(v.v') for the semileptonic decays B->D_1(2420)l\barνand B->D_2^*(2460)l\barνin the framework of heavy quark effective theory. These two universal functions, associated with the matching of the weak currents in QCD onto those in the effective theory, appear at the order 1/m_Q in the heavy quark expansion of meson weak decay form factors.
We study transition form factors for radiative and rare semi-leptonic B-meson decays into light pseudoscalar or vector mesons, combining theoretical constraints and phenomenological information from Lattice QCD, light-cone sum rules, and dispersive bounds. We pay particular attention to form factor parameterisations which are based on the so-called series expansion, and study the related systematic uncertainties on a quantitative level. In this context, we also provide the NLO corrections to the correlation function between two flavour-changing tensor currents, which enters the unitarity const…
We present a QCD sum rule calculation of the spin-symmetry violating universal function $χ_2(v\cdot v')$, which appears at order $1/m_Q$ in the heavy quark expansion of meson form factors. This function vanishes in the standard approximation, where radiative effects are neglected. For the first time, the complete set of diagrams arising at order $α_s$ is evaluated. In particular, we find $χ_2(1) = -(3.8\pm 0.4)\%$ at zero recoil, indicating that $1/m_Q$ corrections induced by the chromo-magnetic moment operator are small.
QED radiative corrections to the cross section of diffractive electro- and photoproduction of vector mesons is calculated at HERA energies. Both semi-analytical and Monte Carlo approaches are discussed and compared.
The impact of final-state radiation (FSR) on the radiative return method for the extraction of the e+e- hadronic cross section is discussed in detail. Possible experimental tests of the model dependence of FSR are proposed for the pi+pi- hadronic final state. The importance of the (pi+pi-photon) final state contribution to the muon anomalous magnetic moment is investigated, and a method based on the radiative return is proposed to extract these contributions from data.
We estimate the rates for radiative transitions of the lightest scalar mesons f_0(980) and a_0(980) to the vector mesons rho and omega. We argue that measurements of the radiative decays of those scalar mesons can provide important new information on their structure.
The electromagnetic radiative correction to the cross section of the vector meson electroproduction is calculated. Explicit covariant formulae for the observed cross section are obtained. The dependence of the radiative correction on the experimental resolution and on the inelasticity cut is discussed. FORTRAN code DIFFRAD based on both exact (ultrarelativistic) and approximate sets of the formulae for the radiative correction to the cross section is presented. The detailed numerical analysis for kinematical conditions of the recent experiments on the diffractive electroproduction of vector me…
B_s-meson double radiative decay $B \to γγ$ is investigated in frame of supersymmetric extension of the standard model. The branching ratio is calculated. It is shown that for light Higgs particle and heigh $\tanβ$ supersymmetric contribution into branching ratio is significunt large than standard model estimate.
The transition form factors of the radiative decays of the heavy tensor mesons to heavy pseudoscalar and heavy vector mesons are calculated in the framework of the light cone QCD sum rules method at the point $Q^2=0$. Using the obtained values of the transition form factors at the point $Q^2=0$ the corresponding decay widths are estimated. The results show that the radiative decays of the heavy--light tensor mesons can be measurable in the future planned experiments at LHCb.
We evaluate the complete spectrum of the Bc mesons, below the open flavor BD threshold, in a Bethe-Salpeter model. We make predictions for the radiative decay widths of the Bc excited states. We compare our results with those of other models.
We review semi-inclusive charmless B decays, focussing on threshold logarithmic resumming and on universality of QCD dynamics in radiative and semileptonic decays.
Using the calculated values of the strong coupling constants of the heavy sextet spin-3/2 baryons to sextet and antitriplet heavy spin-1/2 baryons with light mesons within the light cone QCD sum rules method, and vector meson dominance assumption, the radiative decay widths are calculated. These widths are compared with the "direct" radiative decay widths predicted in the framework of the light cone QCD sum rules.
