Aidos Issadykov
We evaluate $B \rightarrow ρ$ transition form factors in the full kinematical region within the covariant confined quark model. We compare the obtained results with the results from light-cone sum rules. The calculated form factors can be used to calculate the $B^+ \rightarrow ρ^+ μ^+ μ^-$ rare decay branching ratio.
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Decay processes $B\rightarrow D_{\left(s\right)}^{\left(*\right)}h$ ($h=π,ρ$) are studied in the framework of the confined covariant quark model using the naïve factorization assumption. We observe that the theoretical results on branching fractions have tendency to systematically exceed the experimental numbers. Such a behavior has already been seen for similar processes by other authors.
We present a detailed analysis of the heavy-to-light semileptonic decays of the Lambda_b and Lambda_c baryons Lambda_b -> p l- bar(nu)_l and Lambda_c -> n l+ nu_l in the covariant confined quark model. We calculate the invariant and helicity amplitudes of the two processes which are then used to analyze their angular decay distributions, their rates and asymmetry parameters.
B meson decays in covariant confined quark model
本文系统介绍协变禁闭夸克模型（CCQM）的物理原理，并结合实验与理论结果综述其在B介子轻子、半轻子和非轻子衰变中的应用。
Analyzing leptonic decays of heavy quarkonia in covariant confined quark model
本文在协变禁闭夸克模型中研究重夸克偶素轻子衰变，提出基于组分夸克质量跑动与态正交性的径向激发态描述方法，表明标准模型即可解释实验结果。
Motivated by the observation of the decay B to K* gamma by the CLEO collaboration, we have systematically analyzed the weak radiative decay Lambda_b to Lambda gamma, evaluating the confined effects of quarks in the covariant oscillator quark model. This decay process receives both short distance (electromagnetic penguins at the one loop level) the long distance contributions in the quark level. The long distance contributions are analyzed using the vector meson dominance (VMD) method. The estimated branching ratio is found to be 0.23 times 10^-5.
Decay $B_c^+ \to D_{(s)}^{(*)+} \ell^+\ell^-$ within covariant confined quark model
本研究在协变禁闭夸克模型的有效场论框架下，计算$B_c$介子稀有半轻衰变的跃迁形状因子、分支比及多种物理可观测量，并与现有理论结果对比。
In the wake of the recent measurements of the decays $B_c\to J/ψ\,π(K)$ and $B_c\to J/ψ\,\ellν_\ell$ reported by the LHCb Collaboration we calculate the form factors for the $B_c\to J/ψ$ and $B_c\to η_{c}$ transitions in full kinematical region within covariant confined quark model. Then we use the calculated form factors to evaluate the partial decay widths of the above-mentioned semileptonic and nonleptonic decays of the $B_{c}$ meson. We find that the theoretical predictions on the ratios of $\mathcal{R}_{K^{+}/ π^{+}}$ and $\mathcal{R_{π^{+}/ μ^{+} ν}}$ are in good agreement with last LHCb…
We evaluate $B_{s}\rightarrow K^{\ast 0}$ transition form factors in the full kinematical region within the covariant confined quark model. The calculated form factors can be used to calculate the $B_{s}\rightarrow K^{\ast 0}μ^+ μ^-$ rare decay branching ratio, which was recently measured by LHCb collaboration.
We analyze the mixing of the scalar glueball with the scalar-isoscalar quarkonia states above 1 GeV in a non-local covariant constituent approach. Similarities and differences to the point-particle Klein-Gordon limit and to the quantum mechanical case are elaborated. Model predictions for the two-photon decay rates in the covariant mixing scheme are indicated.
In this article, we study the radiative transitions among the vector and scalar heavy quarkonium states with the covariant light-front quark model. In calculations, we observe that the radiative decay widths are sensitive to the constituent quark masses and the shape parameters of the wave-functions, and reproduce the experimental data with suitable parameters.
In this work, we perform a covariant treatment of quark-antiquark systems. We calculate the spectra and wave functions using a formalism based on the Covariant Spectator Theory (CST). Our results not only reproduce very well the experimental data with a very small set of global parameters, but they also allow a direct test of the predictive power of covariant kernels.
$B^{*}_c$ meson parameters and radiative decay width within the covariant confined quark model
本文在协变禁闭夸克模型框架下预测了 $B^{*}_c$ 介子的质量与衰变常数，并计算了 $B^*_{q}$ 介子的辐射衰变宽度，发现 $B_{c}^{*}$ 宽度对质量高度敏感。
Recently there has been much interest in the tauonic semileptonic meson decays B -> D + tau + nu_tau and B -> D* + tau + nu_tau where one has found larger rates than what is predicted by the Standard Model. We analyze the corresponding semileptonic baryon decays Lambda_b(0) -> Lambda_c(+) + tau(-) + antinu_tau with particular emphasis on the lepton helicity flip and scalar contributions which vanish for zero lepton masses. We calculate the total rate, differential decay distributions, the longitudinal and transverse polarization of the daughter baryon Lambda_c(+) and the tau-lepton, and the le…
In this article, we study the rare decays corresponding to $b \to d$ transition in the framework of the covariant confined quark model. The transition form factors for the channels $B^{+(0)} \to (π^{+(0)}, ρ^{+(0)},ω)$ and $B_s^0 \to K^{(*)0}$ are computed in the entire dynamical range of momentum transfer squared. Using the form factors, we compute the branching fractions of the rare decays and our results are found to be matching well with the experimental data. We also compute the ratios of the branching fractions of the $b \to s$ to $b \to d$ rare decays using the inputs from previous pape…
Covariant generalization of the ISGW quark model
构造了一个相当一般的洛伦兹协变夸克模型。它有几个版本，其非相对论极限对应于著名的伊斯古尔，斯科拉，格林斯坦和怀斯模型。在重夸克极限下，协变模型自然自动地给出了介子衰变常数和半轻子衰变形状因子的重夸克对称性结果。介子衰变常数和Isgur-Wise函数的各种版本的协变模型的计算，并与其他估计进行比较。协变模型的一般和适应性强的结构确保了它可以用来描述涉及轻和/或重介子的跃迁。
We present a comparative analysis of chiral quark models which include nonlocal covariant four-fermion couplings. We consider two alternative ways of introducing the nonlocality, as well as various shapes for the momentum-dependent form factors governing the effective interactions. In all cases we study the behavior of model parameters and analyze numerical results for constituent quark masses and quark propagator poles. Advantages of these covariant nonlocal schemes over instantaneous nonlocal schemes and the standard NJL model are pointed out.
Covariant and Heavy Quark Symmetric Quark Models
存在相对论性夸克模型（势或MIT-bag），它们满足介子衰变常数与形状因子之间的重夸克对称性（HQS）关系。本文提出的动量本征态的协变结构可以修正质心运动的贡献，并计算了质子形状因子和夸克偶子中的M1跃迁。明确表达的Isgur-Wise功能和模型确定的偏差从HQS进行了研究。所有结果仅取决于模型参数。不需要额外的特别假设。
Poincare covariant quark models of the the nucleon, the $Δ$ resonance and their excitations are explored. The baryon states are represented by eigenfunctions of the four-velocity and a confining mass operator, which reproduces the empirical spectrum up to $\sim$ 1700 MeV to an accuracy of $\sim 6%$. Models of constituent quark currents provide the relations between ground-state properties and transition amplitudes.
We discuss the relations between TMDs and PDFs in the framework of the covariant parton model. The quark OAM and its connection to TMDs are studied as well.
We calculate magnetic moments of light baryons and N -> Delta gamma transition characteristics using a manifestly Lorentz covariant chiral quark approach for the study of baryons as bound states of constituent quarks dressed by a cloud of pseudoscalar mesons.
Prediction of various observables for $B_s^0 \to D_s^{(*)-}\ell^+ν_\ell$ within covariant confined quark model
本文利用协变禁闭夸克模型，计算了 $B_s^0 \to D_s^{(*)-}\ell^+ν_\ell$ 衰变中前-后不对称性、极化等可观测量，覆盖所有轻子味，并与其它理论预测比较，以探寻新物理迹象。
We calculate the invariant and helicity amplitudes for the nonleptonic decay Lambda_b -> Lambda + J/psi, psi(2S) in the covariant confined quark model. We discuss joint angular decay distributions in the cascade decay Lambda_b -> Lambda(-> p pi-) + J/psi, psi(2S) (-> l+ l-) and calculate some of the asymmetry parameters that characterize the joint angular decay distribution. We confirm expectations from the naive quark model that the transitions into the lambda_Lambda=1/2 helicity states of the daughter baryon Lambda are strongly suppressed leading to a near maximal negative polarization of th…
We discuss QCD condensate contributions to the gluon propagator both in the fixed-point gauge and in covariant gauges for the external QCD vacuum gluon fields with the conclusion that a covariant gauge is essential to obtain a gauge invariant QCD vacuum energy density difference and to retain the unitarity of the quark scattering amplitude. The gauge-invariant QCD condensate contributions to the effective one-gluon exchange potential are evaluated by using the effective gluon propagator which produces a gauge-independent quark scattering amplitude.
We calculate magnetic moments of nucleons and hyperons and N -> Delta + gamma transition characteristics using a manifestly Lorentz covariant chiral quark approach for the study of baryons as bound states of constituent quarks dressed by a cloud of pseudoscalar mesons.
The quark propagator in presence of an arbitrary gluon field is calculated gauge and Lorentz covariantly order by order in terms of powers of gluon field and its derivatives. The result is independent of path connecting ends of propagator and leading order result coincides with the exact propagator in the trivial case of vanishing gluon field.
Spin-dependent and spin-independent quark light-cone momentum distributions and structure functions are calculated for the nucleon. We utilize a modified Nambu-Jona-Lasinio model in which confinement is simulated by eliminating unphysical thresholds for nucleon decay into quarks. The nucleon bound state is obtained by solving the Faddeev equation in the quark-diquark approximation, where both scalar and axial-vector diquark channels are included. We find excellent agreement between our model results and empirical data.
The COMPASS collaboration, as a part of their hadron spectroscopy program, is going to measure the radiative decay widths of light-quark mesons via the Primakoff reactions. In this letter we study the photon couplings of light-quark q qbar states in the covariant oscillator quark model and evaluate the transition rates for {rho(770), b_1(1235), a_1(1260), a_2(1320), pi_2(1670), rho_3(1690), rho(1700)}^pm to pi^pm gamma, which are expected to be measured by the COMPASS. Such photon couplings could be useful not only for understanding the internal structures of observed light-quark mesons and th…
We provide a new insight into the problem of generating the hadron mass spectrum in the framework of the covariant confined quark model. One of the underlying principles of this model is the compositeness condition which means that the wave function renormalization constant of the elementary hadron is equal to zero. In particular, this equation allows to express the Yukawa coupling of the meson fields to the constituent quarks as a function of other model parameters. In addition to the compositeness condition we also employ a further equation which relates the meson mass function to the Fermi …
Assuming the spin-independence for confining force, we give a covariant quark representation of general composite meson systems with definite Lorentz transformation properties. For benefit of this representation we are able to deduce automatically the transformation rules of composite mesons for general symmetry operations from those of constituent (exciton) quarks. Applying this we investigate especially physical implication of chiral symmetry for the meson systems, and point out a possibility of existence of new meson multiplets.
Using a relativistic constituent quark model based on point form of relativistic quantum mechanics with given set of degrees of freedom we investigate electroweak decays of the pion and rho mesons. All free parameters of quark model (the mass u(d) -quark and parameters which determines the confinement scale) are fixed by using relevant experimental data
Transverse parton momentum dependent distribution functions (TMDs) of the nucleon are studied in a covariant model, which describes the intrinsic motion of partons in terms of a covariant momentum distribution. The consistency of the approach is demonstrated, and model relations among TMDs are studied. As a byproduct it is shown how the approach allows to formulate the non-relativistic limit.
We provide details on a recent solution of the nucleon's covariant Faddeev equation in an explicit three-quark approach. The full Poincare-covariant structure of the three-quark amplitude is implemented through an orthogonal basis obtained from a partial-wave decomposition. We employ a rainbow-ladder gluon exchange kernel which allows for a comparison with meson Bethe-Salpeter and baryon quark-diquark studies. We describe the construction of the three-quark amplitude in full detail and compare it to a notation widespread in recent publications. Finally, we discuss first numerical results for t…
The proton and neutron electromagnetic form factors and the nucleon axial form factor have been calculated in the Goldstone-boson exchange constituent-quark model within the point-form approach to relativistic quantum mechanics. The results, obtained without any adjustable parameter nor quark form factors, are, due to the dramatic effects of the boost required by the covariant treatment, in striking agreement with the data.
We present a calculation of the three-quark core contribution to the mass of the Delta-baryon in a Poincare-covariant Faddeev framework. A consistent setup for the dressed-quark propagator, the quark-quark and quark-diquark interactions is used, where all the ingredients are solutions of their respective Dyson-Schwinger or Bethe-Salpeter equations in rainbow-ladder truncation. We discuss the evolution of the Delta mass with the current-quark mass and compare to the previously obtained mass of the nucleon.
We discuss the light-front zero-mode issue in the light-front quark model prediction of the twist-3 distribution amplitude of a pseudoscalar meson from the perspective of the vacuum fluctuation consistent with the chiral symmetry of QCD.
Exclusive nonleptonic bottom meson decays are studied in the covariant osillator quark model using the factorization assumption. The main feature of this model is that it can simultaniously be applied to both heavy to heavy and heavy to light transitions, satisfying the constraints of the heavy quark effective theory (HQET) in the appropriate limit. The results obtained are in overall agreement with the present experimental data for various B decays.
Exclusive weak radiative B meson decays are studied using the covariant oscillator quark model. The branching ratios for the processes B0 to K*0 gamma and B to K* gamma have been estimated. These are in reasonable agreement with the available experimental data. The calculation has been extended to the CKM-suppressed decay processes B- to rho- gamma and Bs to K*0 gamma .
The isoscalar twist-two generalized parton distributions (GPDs) of the pion and the kaon are calculated in a Poincare covariant Bethe-Salpeter constituent quark model. Results are presented for several values of the parameters xi and t. The results satisfy the form factor constraints and the polynomiality condition. For the pion GPD, also the isospin symmetry constraint is fulfilled. The influence of kinematical variables and model parameters on the support of the GPDs is investigated. To this end, the strength parameters and quark masses of the constituent quark model are artificially varied.
We have made a survey of heavy-to-heavy and heavy-to-light nonleptonic heavy baryon two-body decays and have identified those decays that proceed solely via $W$-boson emission, i.e. via the tree graph contribution. Some sample decays are $Ω_{b}^{-}\toΩ_{c}^{(*)0}ρ^{-}(π^{-}),\, Ω_{b}^{-}\toΩ^{-}J/ψ(η_{c}),\, Ξ_{b}^{0,-}\toΞ^{0,-}J/ψ(η_{c}),\, Λ_{b}\to ΛJ/ψ(η_{c}),\, Λ_{b}\to Λ_{c} D_{s}^{(\ast)},\, Ω_{c}^{0}\toΩ^{-}ρ^{+}(π^{+})$, and $Λ_c \to p ϕ$. We make use of the covariant confined quark model previously developed by us to calculate the tree graph contributions to these decays. We calculat…
A family of simply solvable covariant quark models for the baryons is presented. With optimal parameter choices the models reproduce the empirical spectra of the baryons in all flavor sectors to an accuracy of a few percent. Complete spectra are obtained for all states of the strange, charm and beauty hyperons with $L \leq 2$. The magnetic moments and axial coupling constants of the ground state baryons correspond to those of conventional quark models. We construct current-density operators that are consistent with empirical nucleon form factors at low and medium energies.
In this paper we construct a covariant light-front model of heavy mesons within the framework of heavy quark effective theory (HQET). The covariant model consists of the light-front heavy meson bound states constructed in the heavy quark limit with heavy quark symmetry and heavy quark effective theory as its basis. Within this model, the Isgur-Wise function and decay constants in the infinite quark mass limit can be evaluated in a very simple and the most general way. The results are ensured to be consistent with heavy quark symmetry. From the heavy-quark-limit bound states, we can further dev…
Covariant quark model of form factors in the heavy mass limit
我们表明，夸克模型的电流矩阵元素的基础上的Bakamjian-Thomas建设的相对论态与一个固定的粒子数，加上加性假设，是协变的重夸克极限，并满足全套的重夸克对称性关系发现的Isgur和Wise。我们发现，在这种模型中的$ρ^2$的下限是$3/4$的基态介子，独立于任何参数。这些模型的另一个受欢迎的性质是，在无限动量极限下，波函数在$0\le x \le 1$区域之外消失。
Although the meson decay amplitude described by a two-point function may be regarded as one of the simplest possible physical observable, it is interesting that this apparently simple amplitude bears abundant fundamental informations on QCD vacuum dynamics and chiral symmetry. The light-front zero-mode issue of the vector meson decay constant $f_V$ is in this respect highly non-trivial and deserves careful analyses. We discuss the zero-mode issue in the light-front quark model (LFQM) prediction of $f_V$ from the perspective of the vacuum fluctuation consistent with the chiral symmetry of QCD. …
Transversity quark light-cone momentum distributions are calculated for the nucleon. We utilize a modified Nambu--Jona-Lasinio model in which confinement is simulated by eliminating unphysical thresholds for nucleon decay into quarks. The nucleon bound state is obtained by solving the relativistic Faddeev equation in the quark-diquark approximation, where both scalar and axial-vector diquark channels are included. Particular attention is paid to comparing our results with the recent experimental extraction of the transversity distributions by Anselmino et al. We also compare our transversity r…
We extend the investigation of the Generalized Parton Distribution for a charged pion within a fully covariant constituent quark model, in two respects: (i) calculating the tensor distribution and (ii) adding the treatment of the evolution, needed for achieving a meaningful comparison with both the experimental parton distribution and the lattice evaluation of the so-called generalized form factors. Distinct features of our phenomenological covariant quark model are: (i) a 4D Ansatz for the pion Bethe-Salpeter amplitude, to be used in the Mandelstam formula for matrix elements of the relevant …
$B \to K^{(\ast)} ν\barν$ in covariant confined quark model
本文在标准模型框架下，利用协变禁闭夸克模型计算了 $B \to K^{(\ast)} ν\barν$ 衰变的形状因子和分支比，结果与其他理论一致，并指出当前实验上限比理论预言大一个数量级，激励未来实验验证并可能扩展标准模型。
In a covariant model where constituent quarks and diquarks interact through quark exchange, the Bethe-Salpeter equation in ladder approximation for octet and decuplet baryons is solved. Quark and diquark confinement is thereby effectively parametrised by choosing appropriately modified propagators. Numerical results for the baryon masses are presented. In a second step electromagnetic, weak and pionic currents are coupled to the bound state according to Mandelstam's technique. The arising matrix elements are evaluated in a generalised impulse approximation and observable form factors are extra…
The spectra and branching ratios of the weak semi-leptonic B meson decays to the first excited D mesons are predicted, taking into account the confined effects of quarks using the covariant oscillator quark model (COQM). In the COQM the same relation between general weak transition form factors as that in HQET is derived, and the concrete form of the Isgur-Wise function is given with no free parameters. Our results are somewhat different from those of other models. The present experimental data are not sufficient for comparison.
We treat baryons as bound states of scalar or axialvector diquarks and a constituent quark which interact through quark exchange. We obtain fully four-dimensional wave functions for both octet and decuplet baryons as solutions of the corresponding Bethe-Salpeter equation. Applications currently under investigation are: electromagnetic and strong form factors and strangeness production processes.
The work is devoted to the study of b-s anomaly decays. We evaluated branching fractions of $B\to K^\ast μ^+μ^-$, $B^0_s\to ϕμ^+μ^-$ and $B_s\to μ^+μ^-$ decays and compared them with available experimental data and with results from other theoretical approaches.
The baryon structure is investigated in a covariant diquark-quark model. In this approach baryons emerge as relativistic bound states of a constituent quark and a $0^{+}$ or $1^{+}$ diquark. After solving the Bethe-Salpeter Equation for the scalar diquark quark system in ladder approximation we couple various external currents to the constituents of the baryon to probe its internal structure. The quark and the diquarks are assumed to be confined which is implemented by suitable choices for the propagators. This leads to nontrivial vertex functions between the constituents and the external curr…
Two photon decay widths of the $J^P = O^+$ scalar mesons $a_{0} (980)$, $f_{0}(980)$, $f_{0}(1370)$ and $χ_{c0}$ are calculated in a covariant model which is characterized by the quark - antiquark structure. Previously such models were used to calculate current form factors. Here a different application is tried. A simple version of the model uses adjusted nonrelativistic model parameters with small quark masses. The results seem to prefer nonideal mixing of $f_0(980)$ and $f_0(1370)$. The calculated decay rate of $χ_{c0}$ agrees with the experimental results.
An analytic resolution of the covariant oscillator quark model for a three-body system is presented. Our harmonic potential is a general quadratic potential which can simulate both a $δ$-shape configuration or a simplified Y-configuration where the junction is located at the center of mass. The mass formulas obtained are used to compute glueball and baryon spectra. We show that the agreement with lattice and experimental data is correct if the Casimir scaling hypothesis is assumed. It is also argued that our model is compatible with pomeron and odderon approaches.
The relations between TMDs and PDFs are obtained from the symmetry requirement: relativistic covariance combined with rotationally symmetric parton motion in the nucleon rest frame. This requirement is applied in the covariant parton model. Using the usual PDFs as an input, we are obtaining predictions for some polarized and unpolarized TMDs.
The spectra and form factors of exclusive semi-leptonic decays of B-meson are analyzed, taking account of confined effects of quarks by the Covariant Oscillator Quark Model. The predicted B --> (D*,D)l nubar_l spectra with the conventional value of V_cb are fit well to the high-precision experiment. It is also shown the values of V_cb and V_ub obtained through decay widths for the B --> (D,D*,rho)l nubar_l processes are consistent with the presently accepted ones.
We extend the confined covariant constituent quark model that was previously developed by us for mesons to the baryon sector. In our numerical calculation we use the same values for the constituent quark masses and the infrared cutoff as have been previously used in the meson sector. In a first application we describe the static properties of the proton and neutron, and the $Λ$-hyperon (magnetic moments and charge radii) and the behavior of the nucleon form factors at low momentum transfers. We discuss in some detail the conservation of gauge invariance of the electromagnetic transition matrix…
Preliminary calculations using the Covariant Spectator Theory (CST) employed a scalar linear confining interaction and an additional constant vector potential to compute the mesonic mass spectra. In this work we generalize the confining interaction to include more general structures, in particular a vector and also a pseudoscalar part, as suggested by a recent study. A one-gluon-exchange kernel is also implemented to describe the short-range part of the interaction. We solve the simplest CST approximation to the complete Bethe-Salpeter equation, the one-channel spectator equation, using a nume…
The covariant quark model represents an appropriate theoretical framework to describe the recent results on $B_{s}\rightarrow J/ψ+η$ and $B_{s}\rightarrow J/ψ+η'$ decays from the Belle collaboration. In this article we present the main features of he covariant quark model together with details on some of its aspects and methods, which we consider to be important. Further we apply the model specifically to the studied decay processes and give numerical results on decay widths as they follow from the odel. We conclude that the model, with most of its parameters previously fixed from different pr…
Expressions for the nucleon wave functions in the covariant spectator theory (CST) are derived. The nucleon is described as a system with a off-mass-shell constituent quark, free to interact with an external probe, and two spectator constituent quarks on their mass shell. Integrating over the internal momentum of the on-mass-shell quark pair allows us to derive an effective nucleon wave function that can be written only in terms of the quark and diquark (quark-pair) variables. The derived nucleon wave function includes contributions from S, P and D-waves.
Covariant Variable Front Quark Model
我们研究了洛伦兹对称性对强子结构的影响，通过建立一个明显协变的组分夸克模型，发现任何洛伦兹变换都需要利用一个可变的量子化表面。尽管时间反演不变性要求表面的方向有一个独特的方向，我们研究了替代选择，并发现不同方向的数值敏感性很小。我们还计算了低位赝标介子的静态性质，并与现有的非协变计算结果进行了比较。我们的结论是，有一个小的敏感性计算的观测值的选择的形式主义，提供相对论是正确的实施。
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