标准模型有效场论（Standard Model Effective Field Theory，SMEFT）是参数化新物理（New Physics，NP）的通用方法，新物理表现为与标准模型（Standard Model，SM）自由度相互作用的新型重粒子，且这些相互作用遵守SM的规范对称性。NP相互作用中的高阶项可能产生显著效应，这对有意义的唯象研究至关重要，例如对中性介子混合的贡献，这类效应通常会将NP的能标推至远超出对撞机直接探测范围的能量尺度。本文讨论了SMEFT中，改变夸克味数为1单位（即$|ΔF|=1$，$F=$奇异味、粲味或底味）的6维四费米子算符双插入，通过与介子混合相关的8维算符（即$|ΔF|=2$）产生的领头阶重整化。随后，本文考虑了与大汤川耦合成正比的贡献的唯象意义，通过领头对数贡献对6维算符的威尔逊系数设定了限制。鉴于SMEFT在低能下完备描述成熟模型的核心价值，本工作强调在SMEFT的6维算符唯象应用中，有必要纳入8维算符的考量。
英文摘要：
The Standard Model Effective Field Theory (SMEFT) is a universal way of parametrizing New Physics (NP) manifesting as new, heavy particle interactions with the Standard Model (SM) degrees of freedom, that respect the SM gauged symmetries. Higher order terms in the NP interactions possibly lead to sizable effects, mandatory for meaningful phenomenological studies, such as contributions to neutral meson mixing, which typically pushes the scale of NP to energy scales much beyond the reach of direct searches in colliders. I discuss the leading-order renormalization of double-insertions of dimension-6 four-fermion operators that change quark flavor by one unit (i.e., $ | ΔF | = 1 $, $ F = $ strange-, charm-, or bottom-flavor), by dimension-8 operators relevant to meson mixing (i.e., $ | ΔF | = 2 $) in SMEFT. Then, I consider the phenomenological implications of contributions proportional to large Yukawas, setting bounds on the Wilson coefficients of operators of dimension-6 via the leading logarithmic contributions. Given the underlying interest of SMEFT to encode full-fledged models at low energies, this work stresses the need to consider dimension-8 operators in phenomenological applications of dimension-6 operators of SMEFT.
We argued that deep inelastic scattering (DIS) at small values of Q squared is an essentially nonperturbative process and can be described, partially at least, by the vector meson dominance (VMD) model. We showed by the straightforward calculation that VMD model alone can successfully explain data on structure functions of DIS in a broad interval of x (5e-2 - 1e-4) for the region Q squared < 1 GeV squared. For a description of data at larger Q squared we used the two-component (VMD + perturbative QCD) approach. We showed that these two components can be separated if VMD is used in the aligned …
The phenomenological case for threefold maximal lepton mixing is strengthened by more detailed comparison with existing data. The atmospheric neutrino data are self-consistent and in good agreement with the threefold maximal mixing prediction R = 2/3 (chi-squared/dof = 4.3/5, CL = 51%). Including partially con- tained event data, the zenith angle dependence also points to threefold maximal mixing, ruling-out a range of mixing schemes, including that of Fritzsch and Xing. Accounting for `de facto' uncertainties in solar neutrino fluxes, the solar neutrino data (including HOMESTAKE) are shown to…
We re-fit for the neutrino mass-squared difference $Δm^2$ in the threefold maximal (ie. tri-maximal) mixing scenario using recent CHOOZ and SUPER-K data, taking account of matter effects in the Earth. While matter effects have little influence on reactor experiments and proposed long-baseline accelerator experiments with $L \simlt 1000 km$, they are highly significant for atmospheric experiments, suppressing naturally $ν_e$ mixing and enhancing $ν_μ - ν_τ$ mixing, so as to effectively remove the experimental distinction between threefold maximal and twofold maximal $ν_μ-ν_τ$ mixing. Threefold …
The radiative transition form factors of the pseudoscalar mesons {$π$, $η$, $η'$} and the vector mesons {$ρ$, $ω$, $ϕ$} are restudied with $π$-$η$-$η'$ and $ρ$-$ω$-$ϕ$ in tri-meson-mixing pattern, which is described by tri-mixing matrices in the light-cone constituent quark model. The experimental transition decay widths are better reproduced with tri-meson-mixing than previous results in a two-mixing-angle scenario of only two-meson $η$-$η'$ mixing and $ω$-$ϕ$ mixing.
The investigation of mixing phenomena and lifetime in neutral B meson systems provides an important testing ground for standard model flavour dynamics. Spectroscopic parameters has been used to calculate the pseudoscalar decay constant and predictions of mixing mass parameters and lifetimes of the B$_{d}$ and B$_{s}$ mesons.
We use the 1/N_c method to estimate electromagnetic contributions to vector meson masses and mixings. We identify several new sources of rho-omega mixing coming from short-distance effects. We comment on the extraction of quark masses from the vector meson masses. We also present a simple group theoretical discussion of the electromagnetic mass differences.
Calculations in unquenched QCD for the scalar glueball spectrum have confirmed previous results of Gluodynamics finding a glueball at ~ 1750 MeV. I analyze the implications of this discovery from the point of view of glueball-meson mixing at the light of the experimental scalar sprectrum.
We analyze a contribution of the finite-width (mass-smearing) effects to the mixing of neutral mesons. It was shown, that this contribution is dominant in the D-meson system and large in the K-meson one. An account of the mass-smearing effects allows to explain some discrepancy between standard predictions and experimental data in these cases.
The octet-singlet mixing angle $θ_P$ in the pseudoscalar meson nonet is deduced from the rich set of accurate data on $J/ψ$ decays into a vector and a pseudoscalar meson. Corrections due to non-ideal $ω$-$ϕ$ mixing have been included for the first time and turn out to be crucial to find $θ_P = -16.9 \pm 1.7$ degrees, which is appreciably less negative than previous results coming from similar analyses.
Neutral mesons exhibit a phenomenon called flavour mixing. As a consequence of a second order weak process the flavour eigenstates corresponding to the meson and its anti-meson are superpositions of two mass eigenstates. A meson produced in a flavour state changes into an anti-meson and back again as a function of time. Such flavour oscillations are considered sensitive probes of physics beyond the Standard Model. In this brief review I summarize the status of experimental constraints on mixing parameters in the B_s meson system.
We review mixing and CP violation in $D$ mesons, emphasizing the differences with the other pseudoscalar mesons in the Standard Model, and show that $D$ mesons can be useful to look for physics beyond the Standard Model.
The mixing between q-qbar meson and qqbar-qqbar tetra-quark states is examined within an effective QCD Coulomb gauge Hamiltonian model. Mixing matrix elements of the Hamiltonian are computed and then diagonalized yielding an improved prediction for the low-lying J^{PC} = 0^{+/- +}, 1^{--} isoscalar spectra. Mixing effects were found significant for the scalar hadrons but not for the 1^{--} states, which is consistent with the ideal mixing of vector mesons. A perturbative assessment of the exact QCD kernel is also reported.
We explore conventional meson-hybrid mixing in $J^{PC}=1^{++}$ heavy quarkonium using QCD Laplace sum-rules. We calculate the cross-correlator between a heavy conventional meson current and heavy hybrid current within the operator product expansion, including terms proportional to the four- and six-dimensional gluon condensates and the six-dimensional quark condensate. Using experimentally determined hadron masses, we construct models of the $1^{++}$ charmonium and bottomonium mass spectra. These models are used to investigate which resonances couple to both currents and thus exhibit conventio…
A brief review of checking the factorization hypothesis for matrix element of $B^0 - \bar B^0$ mixing within operator product expansion and QCD sum rules is given. Both perturbative and power corrections are considered.
Using the experimental data on meson decay rates, mixing and CP violation we set competitive upper and lower limits to the parameter tan(beta) as a function of the mass of the charged Higgs m_H in the Two Higgs Doublet Model (Model II).
We study mixing between conventional and hybrid mesons in vector and axial vector charmonium using QCD Laplace sum-rules. We compute meson-hybrid cross correlators within the operator product expansion, taking into account condensate contributions up to and including those of dimension-six as well as composite operator renormalization-induced diagrams. Using measured masses of charmonium-like states as input, we probe known resonances for nonzero coupling to both conventional and hybrid meson currents, a signal for meson-hybrid mixing.
Based on the relations from the meson-meson mass mixing matrix, the mixing angles of isoscalar state have been re-evaluated via mass relations and latest experimental results. The results in the present work are compared with the values from different theoretical models, meanwhile, the quarkonia content of isoscalar state are presented. In order to check the validity of analysis, some predictions on the decays of the isoscalar state are presented. These predictions may be useful for the phenomenological analysis for meson nonet in future experiments.
In a nonrelativistic constituent quark model we find a constraint on the mixing angle of the strange axial-vector mesons, $35^o\stackrel{<}{\sim } θ_K\stackrel{<}{\sim }55^o,$ determined solely by two parameters: the mass difference of the $a_1$ and $b_1$ mesons and the ratio of the constituent quark masses.
Following the re-establishment of the σ(600) and the κ(900), the light scalar mesons a_0(980) and f_0(980) together with the σ(600) and the κ(900) are considered as the chiral scalar partner of pseudoscalar nonet in SU(3) chiral symmetry, and the high mass scalar mesons a_0(1450), K^*_0(1430), f_0(1370) and f_0(1710) turned out to be considered as the L=1 q\bar{q} scalar mesons. We assume that the high mass of the L=1 q\bar{q} scalar mesons is caused by the mixing with the light scalar mesons. For the structure of the light scalar mesons, we adopted the qq\bar{q}\bar{q} model in order to expla…
Usually, neutrino oscillation experiments are analyzed within the two-flavor framework which is governed by 1 mass-squared difference and 1 mixing angle. But there are 6 parameters,2 mass-squared differences, 3 mixing angles, and 1 CP phase within the three-flavor framework.In this article,we estimate the effect from the smaller mass-squared difference,the other mixing angles, and the CP phase, which we call three-flavor effect, for the determination of the mass-squared difference and the mixing angle from the nu_mu's survival and transition probability with the two-flavor analysis.It is found…
Replacing the perturbative vacuum by the nonperturbative vacuum, we extend a recent development of a quantum field theoretic framework for scalar and pseudoscalar meson mixing. The unitary inequivalence of the Fock space of base (unmixed) eigenstates and the physical mixed eigenstates is investigated and the flavor vacuum state structure is explicitly found. This is exploited to develop formulas for two flavor boson oscillations in systems of arbitrary boson occupation number. We apply these formulas to analyze the mixing of eta with eta' and comment on the other meson-mixing systems. In addit…
We calculate the branching ratio of omega --> pi^+ pi^- gamma decay in a phenomenological framework in which the contributions of VMD, chiral loops, sigma-meson intermediate state amplitudes and the effects of omega-rho mixing are considered. We conclude that the sigma-meson intermediate state amplitude and omega-rho mixing make substantial contribution to the branching ratio.
I present a simple discussion of the masses and mixings of the light pseudoscalar and vector mesons based on a ``$q\bar{q}$'' description of the effective field theory. The analysis includes $η'$(958) from the beginning, and is largely concerned with structural questions. While the final results are mostly known, the method gives insight into the general form of the meson mass matrices and the different character of the mass splittings and mixings in the pseudoscalar and vector multiplets, and provides a coherent overall picture
The new BES measurement on the two-body decays of J/psi and psi' into an axial-vector meson and a pseudoscalar meson is analyzed with the axial-K mixing including the one-photon annihilation contribution. A somewhat puzzling pattern of the K_1^+ K^- decay channels can be understood with no tight constraint on the mixing angle. The branching fractions of the K_1^0 K-bar^0 channels will be the cleanest source of information to determine the mixing angle from the 1^+ 0^- decays of J/psi and psi'.
We update the analysis of $D$ meson mixing including the latest experimental results as of January 2014. We derive constraints on the parameters $M_{12}$, $Γ_{12}$ and $Φ_{12}$ that describe $D$ meson mixing using all available data, allowing for CP violation. We also provide posterior distributions for observable parameters appearing in $D$ physics.
We use QCD Laplace sum-rules to explore mixing between conventional mesons and hybrids in the heavy quarkonium vector $J^{PC}\!=\!1^{--}$ channel. Our cross-correlator includes perturbation theory and contributions proportional to the four-dimensional and six-dimensional gluon condensates. We input experimentally determined charmonium and bottomonium hadron masses into both single and multi-resonance models in order to test them for conventional meson and hybrid components. In the charmonium sector we find evidence for meson-hybrid mixing in the $J/ψ$ and a $\approx4.3$ GeV resonance. In the b…
We discuss pure $q\bar{q}$ axial-vector mesons in the Tamm-Dancoff approximation of the Coulomb-gauge QCD model from NCSU. While recent studies have put emphasis in configuration mixing with open meson-meson channels, we here concentrate on the simpler closed-channel problem and follow the $1^+$ mixing through a wide range of quark masses. We also examine their radial excitations and discuss with them the concept of insensitivity to chiral symmetry breaking.
We study $\bar qq$-hybrid mixing for the light vector mesons and $\bar qq$-glueball mixing for the light scalar mesons in Monte-Carlo based QCD Laplace sum rules. By calculating the two-point correlation function of a vector $\bar qγ_μq$ (scalar $\bar q q$) current and a hybrid (glueball) current we are able to estimate the mass and the decay constants of the corresponding mixed "physical state" that couples to both currents. Our results do not support strong quark/gluonic mixing for either the $1^{--}$ or the $0^{++}$ states.
We analyze the mass spectroscopy of low and high mass scalar mesons and get the result that the coupling strengths of the mixing between low and high mass scalar mesons are very strong and the strengths of mixing for $I=1, 1/2$ scalar mesons and those of I=0 scalar mesons are almost same. Next, we analyze the decay widths and decay ratios of these mesons and get the results that the coupling constants $A'$ for $I=1, 1/2$ which represents the coupling of high mass scalar meson $N'$ -> two pseudoscalar mesons $PP$ are almost same as the coupling $A'$ for the I=0. On the other hand, the coupling …
In this paper, U(3)$_L\times$ U(3)$_R$ chiral theory of mesons is extended to the leading order in quark mass expansion in order to evaluate the $ρ^0-ω$ mixing. It is shown that the use of path integral method to integrate out the quark fields naturally leads to the $ρ^0-ω$ mixing vertices, and this mixing is entirely from the quark loop in this theory. The off-shell behaviour of the mixing amplitude is analyzed. The on-shell mixing amplitude is obtained from the decay $ω\to π^+π^-$. Furthermore, the constraints on the light quark mass parameters are extracted from the $ρ^0-ω$ mixing and the m…
The QCD anomaly leads to an abnormal mixing and mass pattern for the pseudoscalar mesons. Furthermore it is responsible for the quality of isospin symmetry in the meson spectrum. Similarities between the large mixing angles among the neutral 0^-+ mesons and the large mixing angles observed in neutrino oscillations are pointed out.
The SU(3)-flavor symmetry breaking and the quark-antiquark annihilation mechanism are taken into account for describing the singlet-octet mixing for several nonets assigned by Particle Data Group(PDG). This task is approached with the mass matrix formalism.
We consider the hypothesis of a priori mixings in the mass eigenstates of mesons to obtain the |Delta I|=1/2 rule in K\toππ. The Hamiltonian responsible for the transition is the strong interacting one. The experimental data are described using the isospin symmetry relations between the strong coupling constants.
I give an introduction to the theory of meson-antimeson mixing, aiming at students who plan to work at a flavour physics experiment or intend to do associated theoretical studies. I derive the formulae for the time evolution of a neutral meson system and show how the mass and width differences among the neutral meson eigenstates and the CP phase in mixing are calculated in the Standard Model. Special emphasis is laid on CP violation, which is covered in detail for K mixing, Bd mixing and Bs mixing. I explain the constraints on the apex (rho-bar,eta-bar) of the unitarity triangle implied by eps…
A fit of amplitudes to the experimental branching ratios to two mesons is used to construct a new estimate of neutral $D$ mixing which includes $SU(3)$ breaking. The result is dominated by the experimental uncertainties. This suggests that the charm sector may not be as sensitive to new physics as previously thought and that long-distance calculations may not be useful.
Neutral meson mixing and $CP$ violation are very well known weak processes that involve decays to meson states that are, in general, a superposition of flavor eigenstates. This paper describes a mathematical interpretation of the time-dependent mixing amplitudes as a complex hyperbolic rotation of the time evolution of those amplitudes without mixing, which involves a Lie group $SO(1,1,\mathbb{C})$. This allows a geometric interpretation of mixing as a curve into the $SO(1,1,\mathbb{C})$ manifold, parameterized with the proper decay time, where $CP$ violation is the image of this curve at $t =…
Assuming one nonzero product of two $λ'$-type couplings and working in two different bases for the left-handed quark superfields, the neutral meson mixings are used to bound these products. We emphasize the strong basis dependence of the bounds: in one basis many products contribute to neutral meson mixings at tree level, while in the other these products except one contribute at 1-loop level only and the GIM mechanism takes place. Correspondingly, these bounds differ between bases by orders of magnitudes.
In this work we study the departure for the ideal $ϕ-ω$ mixing angle in the frame of the Nambu-Jona-Lasinio model. We have shown that in that context, the flavour symmetry breaking is unable to produce the shifting in the mixing angle. We introduce a nonet symmetry breaking in the neutral vector sector to regulate the non-strange content of the $ϕ$ meson. The phenomenon is well reproduced by our proposal.
It is shown that the QCD anomaly may lead to an abnormal mixing behavior of the axial vector mesons similar to the pseudoscalar mesons. These mixing effects, involving a gluonic axial vector state, generate a non-vanishing strange quark component in the nucleon. They reduce the matrix element of the singlet axial vector in comparison to the value obtained in a naive quark model. The results are in agreement with the data obtained in the polarized lepton-nucleon scattering experiments.
We derive constraints on the parameters $M_{12}$, $Γ_{12}$ and $Φ_{12}$ that describe $D$ meson mixing using all available data, allowing for CP violation. We also provide posterior distributions and predictions for observable parameters appearing in $D$ physics.
The color mixing of mesons propagating in a nucleus is studied with the help of a color-octet Pomeron partner present in the two-gluon model of the Pomeron. For a simple model with four meson-nucleon channels, color mixings are found to be absent for pointlike mesons and very small for small mesons. These results seem to validate the absorption model with two independent color components used in recent analyses of the nuclear absorption of $J/ψ$ mesons produced in nuclear reactions.
Recent work by Burdman, Lane, and Rador has shown that B-meson mixing places stringent lower bounds on the masses of topgluons and Z' bosons in classic topcolor-assisted technicolor (TC2) models. This paper finds analogous limits on the Z' bosons of flavor-universal TC2 and non-commuting extended technicolor models, and compares the limits with those from precision electroweak measurements. A discussion of the flavor structure of these models (contrasted with that of classic TC2) shows that B-meson mixing is a less reliable probe of these models than of classic TC2.
It is shown that the diagonalization of the axial-vector -- pseudoscalar transitions in the effective meson Lagrangian in presence of electromagnetic interactions leads to a deviation from the vector meson dominance picture which usually arises in the Nambu - Jona-Lasinio model. The essential features of such modification of the theory are studied. Some important examples are considered in detail.
We use QCD Laplace sum-rules to study meson-hybrid mixing in vector ($1^{--}$) heavy quarkonium. We compute the QCD cross-correlator between a heavy meson current and a heavy hybrid current within the operator product expansion. In addition to leading-order perturbation theory, we include four- and six-dimensional gluon condensate contributions as well as a six-dimensional quark condensate contribution. We construct several single and multi-resonance models that take known hadron masses as inputs. We investigate which resonances couple to both currents and so exhibit meson-hybrid mixing. Compa…
The mixing of $S-D$ partial waves for the heavy meson pairs in the decays $Υ(5S) \to [B^* \bar B+ {\rm c.c.}] π$ and $Υ(5S) \to B^* \bar B^* π$ is considered. It is argued that this mixing, enhanced by the heavy meson mass, is calculable as dominated by a rescattering through pion exchange if the production of the heavy mesons is dominated by $S$-wave `molecular' resonances $Z_b(10610)$ and $Z_b(10650)$. The effect of the mixing grows with the c.m. energy $E$ in each channel over the threshold, and may reach $10 ÷20$% in the rate at the upper end of applicability of the discussed approach, $E …
We analyze the effect of flavor changing neutral currents within 331 models. In particular, we concentrate in the so-called "economical" models, which have a minimal scalar sector. Taking into account the experimental measurements of observables related to neutral K and B meson mixing, we study the resulting bounds for angles and phases in the mixing matrix for the down quark sector, and the mass and mixing parameters related to the new Z' gauge boson.
An update profile of the CKM matrix is given, providing numerical and graphical constraints on the CKM parameters in the Standard Model. Constraints on additional parameters accounting for possible new physics contribution in a model-independent analysis are also reported with emphasis on the leptonic decay of the Bd and on the Bs mixing phase.
We analyze the experimental data for $ϕ\to f_0(980)γ$, $ϕ\to a_0(980)γ$, $f_0(980)\toγγ$ and $a_0(980)\toγγ$ decay widths in a framework where $f_0(980)$ and $a_0(980)$ are assumed to be mainly $qq\bar{q}\bar{q}$ low mass scalar mesons and mixed with $q\bar{q}$ high mass scalar mesons. Applied the vector meson dominance model (VDM), these decays amplitudes are expressed by coupling parameters $B$ describing the S ($qq\bar{q}\bar{q}$ scalar meson)-V(vector meson)- V(vector meson) coupling and $B'$ describing the S' ($q\bar{q}$ scalar meson)-V-V coupling. Adopting the magnitudes for $B$ and $B'$…
Involving of elastic rescattering and annihilation of quark-antiquark pairs in a final state allows us to explain a dependence of ratio for cross sections of $η'$ and $η$ mesons versus transfer momentum in charge exchange reactions. We estimate the mixing angle of mesons with isoscalar states of $\bar u u+\bar d d$ and $\bar s s$ of hidden strangeness. The evaluation includes the consistent description of yield ratio for $η'$ and $η$ mesons in decays of $B^0$, $B^0_s$ and $J/ψ$ mesons.
Mixing effects on the mass spectrum of light neutral pseudoscalar and vector mesons in the presence of an external uniform magnetic field $\vec B$ are studied in the framework of a two-flavor NJL-like model. The model includes isoscalar and isovector couplings both in the scalar-pseudoscalar and vector sectors, and also incorporates flavor mixing through a 't Hooft-like term. Numerical results for the $B$ dependence of meson masses are compared with present lattice QCD results. In particular, it is shown that the mixing between pseudoscalar and vector meson states leads to a significant reduct…
Pion emitting decays and radiative ones of D^{*+,0} and D_s^{*+} are studied. As the result, the full-width of D^{*0} is predicted, by assuming the isospin symmetry. In addition, the isospin non-conserving D_s^{*+} --> D_s^+ pi^0 decay is investigated under the assumption that it proceeds through the eta-pi^0 mixing.
Meson properties are considered within a U(3)\times U(3) Linear Sigma Model(LSM). The importance of the U_A(1)-breaking term and the OZI rule violating term in the generation of meson masses and mixing angles is stressed. The LSM parameters are fitted to the pseudoscalar meson spectrum thus giving predictions for scalar meson properties. The model predicts a scalar meson nonet whose members are: {σ(\approx 400), f_0(980), κ(\approx 900) and a_0(980)} resonances. Scalar meson mixing angle (in the {|ns>, |s>} basis) is predicted to be ϕ_S\approx -14^\circ. Therefore the f_0(980) is predominantly…
Mixings of 4-quark components in the non-singlet scalar mesons are studied in the QCD sum rules. We propose a formulation to evaluate the cross correlators of q\bar q and qq\bar q \bar q operators and to define the mixings of different Fock states in the sum rule. It is applied to the non-singlet scalar mesons, a_0 and K_0^\ast. It is found that the 4-quark operators predict lower masses than the q\bar q operators and that the 4-quark states occupy about 70-90% of the lowest mass states.
The Kawai model describing the glueball-quarkonia mixing is modified. The mixing of $η$, $η^\prime$ and $η(1410)$ is re-investigated based on the modified Kawai model. The glueball-quarkonia content of the three states is determined from a fit to the data of the electromagnetic decays involving $η$, $η^\prime$. Some predictions about the electromagnetic decays involving $η(1410)$ are presented.
This paper is the SU(3) extension of the dynamically generated SU(2) linear $σ$ model Lagrangian worked out previously using dimensional regularization. After discussing the quark-level Goldberger-Treiman relations for SU(3) and the related gap equations, we dynamically generate the meson cubic and quartic couplings. This also constrains the meson-quark coupling constant to $g=2π/\sqrt3$ and determines the SU(3) scalar meson masses in a Nambu-Jona-Lasinio fashion. Finally we dynamically induce the U(3) pseudoscalar and scalar mixing angles in a manner compatible with data.
We present further tests and applications of the new eta-eta' mixing scheme recently proposed by us. The particle states are decomposed into orthonormal basis vectors in a light-cone Fock representation. Because of flavor symmetry breaking the mixing of the decay constants can be identical to the mixing of particle states at most for a specific choice of this basis. Theoretical and phenomenological considerations show that the quark flavor basis has this property and allows, therefore, for a reduction of the number of mixing parameters. A detailed comparison with other mixing schemes is also p…
In the present work, the mixing angle of the vector $ω(782)$ and $ϕ(1020)$ mesons is estimated in the framework of Nambu--Jona-Lasinio model. The decay $ϕ\to π^{0} γ$ is considered as a basic process to determine this angle. The obtained value is compared with the results of the other authors. Besides, the width of the decay $ϕ\to 3π$ and the cross-section of the process $e^{+}e^{-} \to π^{0} ϕ$ are calculated by using this angle.
We investigate f_0-sigma mixing in the framework of light cone QCD sum rules and by employing the experimental results about the decay widths and the masses of these scalar mesons we estimate the scalar mixing angle by using sigma meson data and f_0 meson data. The two values we thus obtain of the scalar mixing angle are not entirely consistent with each other, possibly indicating that the structure of these mesons cannot be simple quark-antiquark states.
The effective QCD Hamiltonian is constructed with the help of the background perturbation theory, and relativistic Feynman--Schwinger path integrals for Green's functions. The resulting spectrum displays mass gaps of the order of one GeV, when additional valence gluon is added to the bound state. Mixing between meson, hybrid, and glueball states is defined in two ways: through generalized Green's functions and via modified Feynman diagram technic giving similar answers. Results for mixing matrix elements are numerically not large (around 0.1 GeV) and agree with earlier analytic estimates and l…
