Decay Constants Of Vector Mesons Research Articles

Independence of current components, polarization vectors, and reference frames in the light-front quark model analysis of meson decay constants

The issue of resulting in the same physical observables with different current components, in particular from the minus current, has been challenging in the light-front quark model (LFQM) even for the computation of the two-point functions such as meson decay constants. At the level of one-body current matrix element computation, we show the uniqueness of pseudoscalar and vector meson decay constants using all available components including the minus component of the current in the LFQM consistent with the Bakamjian-Thomas construction. Regardless of the current components, the polarization vectors, and the reference frames, the meson decay constants are uniquely determined in the noninteracting constituent quark and antiquark basis while the interactions of the constituents are added to the meson mass operator in the LFQM.

Masses and decay constants of (axial-)vector mesons at finite chemical potential

We update our previous results for (pseudo-)scalar mesons at zero temperature and finite quark chemical potential and generalize the investigation to include (axial-)vector mesons. We determine bound-state properties such as meson masses and decay constants up to chemical potentials far in the first-order coexistence region. To extract the bound-states properties, we solve the Bethe-Salpeter equation and utilize Landau-gauge quark and gluon propagators obtained from a coupled set of (truncated) Dyson-Schwinger equations with N_{text{ f }}=2+1 dynamical quark flavors at finite chemical potential and vanishing temperature. For multiple (pseudo-)scalar and (axial-)vector mesons, we observe constant masses and decay constants for chemical potentials up to the coexistence region of the first-order phase transition thus verifying explicitly the Silver-Blaze property of QCD. Inside the coexistence region the pion becomes more massive and its decay constants decrease, whereas corresponding quantities for the (axial-)vector mesons remain (almost) constant.

Mesons and Glueballs, the Strong Effective Coupling within Analytic Confinement

The phenomena of hadron mass generating, strong running coupling and radiative transitions of charmonium excited states have been studied in the framework of a relativistic field model with analytic confinement. A meson mass equation is derived and a specific new behavior of the mass-dependent strong coupling $$\mathop {\bar {\alpha }}\nolimits_s $$ is revealed in the time-like region. A new infrared fixed point $$\mathop {\bar {\alpha }}\nolimits_s (0) = 1.032$$ has been found at origin. Independent and new estimates on the scalar glueball mass, radius and gluon condensate value have been performed. The spectrum of conventional mesons have been calculated by introducing a minimal set of parameters with relative errors less than 1.8 percent compared to the latest data. Accurate estimates of the leptonic decay constants of pseudoscalar and vector mesons have also been performed. Partial decay widths of the dominant radiative transitions of the charmonium orbital excitations have been estimated with reasonable accuracy.

Dalitz decays of vector mesons in relativistic quark model

In the course of work, basing on the previously developed method for calculating integral representations of decay constants for pseudoscalar and vector mesons in the frame of point form of Poincare-covariant quark model, the research of ω- and ϕ-mesons decays form-factors for Dalitz decays has been carried out. It is shown that the usage of the pseudoscalar density constant with integral representations of decay constants , and leads to parameters which can be used for the study of decay form-factors. As a result of the work, the behaviour of (t) Fωπγ* (t) and Fϕηγ* (t) form-factors compared with the experimental data in the interval q < 0.5 GeV is researched.

Form factors of V\u2032 \u2192 V\u2033 transition within the light-front quark models

In this paper, we calculate the matrix element and form factors of vector-to- vector (VI→ VII) transition within the standard light-front (SLF) and covariant light- front (CLF) quark models (QMs), and investigate the self-consistency and Lorentz covari- ance of the CLF QM within two types of correspondences between the manifest covariant Bethe-Salpeter approach and the LF approach. The zero-mode and valence contributions to the form factors of VI→ VII transition in the CLF QM and their relation to the SLF results are analyzed, and the main conclusions obtained via the decay constants of vector and axial-vector mesons and the form factors of P → V transition in the previous works are confirmed again. Furthermore, we present our numerical predictions for the form factors of c → (q, s) (q = u, d) induced D*→ (K*, ρ), D∗→ (ϕ, K*), J/Ψ → left({D}_s^{ast },{D}^{ast}right) , {B}_c^{ast}to left({B}_s^{ast },{B}^{ast}right) transitions and b → (c, s, q) induced B∗ → (D∗, K∗, ρ), {B}_s^{ast}to left({D}_s^{ast },phi, {K}^{ast}right) , {B}_c^{ast}to left(J/varPsi, {D}_s^{ast },{D}^{ast}right),varUpsilon (1S)to left({B}_c^{ast },{B}_s^{ast },{B}^{ast}right) the relevant phenomenological studies of meson decays.

Properties of vector and axial-vector mesons in a nonlocal SU(2) PNJL model

We study the features of a SU(2) Polyakov-Nambu-Jona-Lasinio model that includes wave function renormalization and nonlocal vector interactions. Within this framework we analyze, among other properties, the masses, width and decay constants of light vector and axial-vector mesons at finite temperature. Then we obtain the corresponding phase diagram in a finite density scenario, after characterizing the deconfinement and chiral restoration transitions.

Decays of light mesons in the relativistic quark model

In the framework of the relativistic quark model based on the point form of the Poincaré-invariant quantum mechanics, the parameters were fixed using the integral representations of the lepton decay constants of pseudoscalar and vector mesons containing u-, d- and s-quarks. As a result of numerical calculations using the oscillator wave function, the basic parameters of the model are obtained using the pseudoscalar density constant and current quark masses. The analysis showed that the obtained calculation results in the framework of the model and the experimental data on the lepton decays of hadrons agree well with each other. As a result, the calculation method is generalized to the case of hadronic transitions with γ-quantum emission and a subsequent calculation of the integral representations of radiative decay constants of pseudoscalar and vector mesons. The obtained values of the anomalous magnetic moments are compared with the baryon data. As a test of the model, the authors studied the behavior of the form-factors of radiative decays of vector mesons with a subsequent comparison to the modern experimental data in the q &lt; 0.5 GeV range where the resonance effects are insignificant. As a result, self-consistent descriptions of lepton and radiative transitions were obtained within the framework of the model proposed by the authors.

Revisiting the form factors of Prightarrow V transition within the light-front quark models

We investigate the self-consistency and Lorentz covariance of the covariant light-front quark model (CLF QM) via the matrix elements and form factors ({{mathcal {F}}}=g, a_{pm } and f) of Prightarrow V transition. Two types of correspondence schemes between the manifest covariant Bethe–Salpeter approach and the light-front quark model are studied. We find that, for a_{-}(q^2) and f(q^2), the CLF results obtained via lambda =0 and ± polarization states of vector meson within the traditional type-I correspondence scheme are inconsistent with each other; and moreover, the strict covariance of the matrix element is violated due to the nonvanishing spurious contributions associated with noncovariance. We further show that such two problems have the same origin and can be resolved simultaneously by employing the type-II correspondence scheme, which advocates an additional replacement Mrightarrow M_0 relative to the traditional type-I scheme; meanwhile, the results of {{mathcal {F}}}(q^2) in the standard light-front quark model (SLF QM) are exactly the same as the valence contributions and equal to numerally the full results in the CLF QM, i.e., [{{mathcal {F}}}]_{mathrm{SLF}}=[{{mathcal {F}}}]_{mathrm{val.}}doteq [{{mathcal {F}}}]_mathrm{full}. The numerical results for some Prightarrow V transitions are updated within the type-II scheme. Above findings confirm the conclusion obtained via the decay constants of vector and axial-vector mesons in the previous works.

Strong Effective Coupling, Meson Ground States, and Glueball within Analytic Confinement

The phenomena of strong running coupling and hadron mass generating have been studied in the framework of a QCD-inspired relativistic model of quark-gluon interaction with infrared-confined propagators. We derived a meson mass equation and revealed a specific new behavior of the mass-dependent strong coupling α ^ s ( M ) defined in the time-like region. A new infrared freezing point α ^ s ( 0 ) = 1.03198 at origin has been found and it did not depend on the confinement scale Λ &gt; 0 . Independent and new estimates on the scalar glueball mass, ‘radius’ and gluon condensate value have been performed. The spectrum of conventional mesons have been calculated by introducing a minimal set of parameters: the masses of constituent quarks and Λ . The obtained values are in good agreement with the latest experimental data with relative errors less than 1.8 percent. Accurate estimates of the leptonic decay constants of pseudoscalar and vector mesons have been performed.

Self-consistency and covariance of light-front quark models: Testing via P , V , and A meson decay constants, and P→P weak transition form factors

In this paper, we test the self-consistencies of the standard and the covariant light-front quark model and study the zero-mode issue via the decay constants of pseudoscalar ($P$), vector ($V$) and axial-vector ($A$) mesons, as well as the $P\to P$ weak transition form factors. With the traditional type-I correspondence between the manifestly covariant and the light-front approach, the resulting $f_{V}$ as well as $f_{^1\!A}$ and $f_{^3\!A}$ obtained with the $\lbd=0$ and $\lbd=\pm$ polarization states are different from each other, which presents a challenge to the self-consistency of the covariant light-front quark model. However, such a self-consistency problem can be "resolved" within the type-II scheme, which requires an additional replacement $M\to M_0$ relative to the type-I case. Moreover, the replacement $M\to M_0$ is also essential for the self-consistency of the standard light-front quark model. In the type-II scheme, the valence contributions to the physical quantities~(${\cal Q}$) considered in this paper are alway the same as that obtained in the standard light-front quark model, $[{\cal Q}]_{\rm val.}=[{\cal Q}]_{\rm SLF}$, and the zero-mode contributions to $f_{V,^1\!A,^3\!A}$ and $f_-(q^2)$ exist only formally but vanish numerically, which implies further that $[{\cal Q}]_{\rm val.}\dot{=} [{\cal Q}]_{\rm full}$. In addition, the manifest covariance of the covariant light-front quark model is violated in the traditional type-I scheme, but can be recovered by taking the type-II scheme.

Decay constants of pseudoscalar and vector mesons with improved holographic wavefunction**Supported by National Natural Science Foundation of China (11475055, 11675061, 11435003), Q. Chang is also supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China (201317), the Program for Science and Technology Innovation Talents in Universities of Henan Province (14HASTIT036), the Excellent Youth Foundation of HNNU.

We calculate the decay constants of light and heavy-light pseudoscalar and vector mesons with improved soft-wall holographic wavefuntions, which take into account the effects of both quark masses and dynamical spins. We find that the predicted decay constants, especially for the ratio fV/fP, based on light-front holographic QCD, can be significantly improved, once the dynamical spin effects are taken into account by introducing the helicity-dependent wavefunctions. We also perform detailed χ2 analyses for the holographic parameters (i.e. the mass-scale parameter κ and the quark masses), by confronting our predictions with the data for the charged-meson decay constants and the meson spectra. The fitted values for these parameters are generally in agreement with those obtained by fitting to the Regge trajectories. At the same time, most of our results for the decay constants and their ratios agree with the data as well as the predictions based on lattice QCD and QCD sum rule approaches, with only a few exceptions observed.

Local-duality QCD sum rules for strong isospin breaking in the decay constants of heavy\u2013light mesons

We discuss the leptonic decay constants of heavy–light mesons by means of Borel QCD sum rules in the local-duality (LD) limit of infinitely large Borel mass parameter. In this limit, for an appropriate choice of the invariant structures in the QCD correlation functions, all vacuum-condensate contributions vanish and all nonperturbative effects are contained in only one quantity, the effective threshold. We study properties of the LD effective thresholds in the limits of large heavy-quark mass m_Q and small light-quark mass m_q. In the heavy-quark limit, we clarify the role played by the radiative corrections in the effective threshold for reproducing the pQCD expansion of the decay constants of pseudoscalar and vector mesons. We show that the dependence of the meson decay constants on m_q arises predominantly (at the level of 70–80%) from the calculable m_q-dependence of the perturbative spectral densities. Making use of the lattice QCD results for the decay constants of nonstrange and strange pseudoscalar and vector heavy mesons, we obtain solid predictions for the decay constants of heavy–light mesons as functions of m_q in the range from a few to 100 MeV and evaluate the corresponding strong isospin-breaking effects: f_{D^+} - f_{D^0}=(0.96 pm 0.09) mathrm{MeV}, f_{D^{*+}} - f_{D^{*0}}= (1.18 pm 0.35) mathrm{MeV}, f_{B^0} - f_{B^+}=(1.01 pm 0.10) mathrm{MeV}, f_{B^{*0}} - f_{B^{*+}}=(0.89 pm 0.30) mathrm{MeV}.

Bottomonium dissociation in a finite density plasma

We present a holographic description of the thermal behavior of bb¯ heavy vector mesons inside a plasma at finite temperature and density. The meson dissociation in the medium is represented by the decrease in the height of the spectral function peaks. In order to find a description for the evolution of the quasi-states with temperature and chemical potential it is crucial to use a model that is consistent with the decay constant behavior. The reason is that the height of a spectral function peak is related to the value of the zero temperature decay constant of the corresponding particle. AdS/QCD holographic models are in general not consistent with the observation that decay constants of heavy vector mesons decrease with radial excitation level. However, it was recently shown that using a soft wall background and calculating the correlation functions at a finite position of anti-de Sitter space, associated with an ultraviolet energy scale, it is possible to describe the observed behavior. Here we extend this proposal to the case of finite temperature T and chemical potential μ. A clear picture of the dissociation of bottomonium states as a function of μ and T emerges from the spectral function. The energy scales where the change in chemical potential leads to changes in the thermal properties of the mesons is consistent with QCD expectations.

Holographic picture of heavy vector meson melting

The fraction of heavy vector mesons produced in a heavy ion collision, as compared to a proton proton collision, serves as an important indication of the formation of a thermal medium, the quark gluon plasma. This sort of analysis strongly depends on understanding the thermal effects of a medium like the plasma on the states of heavy mesons. In particular, it is crucial to know the temperature ranges where they undergo a thermal dissociation, or melting. AdS/QCD models are know to provide an important tool for the calculation of hadronic masses, but in general are not consistent with the observation that decay constants of heavy vector mesons decrease with excitation level. It has recently been shown that this problem can be overcome using a soft wall background and introducing an extra energy parameter, through the calculation of correlation functions at a finite position of anti-de Sitter space. This approach leads to the evaluation of masses and decay constants of S wave quarkonium states with just one flavor dependent and one flavor independent parameters. Here we extend this more realistic model to finite temperatures and analyse the thermal behavior of the states $1S, 2S$ and $ 3S$ of bottomonium and charmonium. The corresponding spectral function exhibits a consistent picture for the melting of the states where, for each flavor, the higher excitations melt at lower temperatures. We estimate for these six states, the energy ranges in which the heavy vector mesons undergo a transition from a well defined peak in the spectral function to complete melting in the thermal medium. A very clear distinction between the heavy flavors emerges, with bottomonium state $\Upsilon (1S)$ surviving deconfinemet transition at temperatures much larger than the critical deconfinement temperature of the medium.

Some heavy vector and tensor meson decay constants in light-front quark model

We study the decay constants ( $$f_M$$ ) of the heavy vector ( $$D^{*}$$ , $$D^{*}_{s}$$ , $$B^{*}$$ , $$B^{*}_{s}$$ , $$B^{*}_{c}$$ ) and tensor ( $$D_{2}^{*}$$ , $$D_{s2}^{*}$$ , $$B^{*}_{2}$$ , $$B^{*}_{s2}$$ ) mesons in the light-front quark model. With the known pseudoscalar meson decay constants of $$f_D$$ , $$f_{D_s}$$ , $$f_B$$ , $$f_{B_s}$$ , and $$f_{B_c}$$ as the input parameters to determine the light-front meson wave functions, we obtain $$f_{D^{*}, D^{*}_{s}, B^{*},B^{*}_s,B^{*}_c} = (252.0^{+13.8}_{-11.6}$$ , $$318.3^{+15.3}_{-12.6}$$ , $$201.9^{+43.2}_{-41.4}$$ , $$244.2\pm 7.0$$ , $$473.4\pm 18.2$$ ) and $$(264.9^{+10.2}_{-9.5}$$ , $$330.9^{+9.9}_{-9.0}$$ , $$220.2^{+49.1}_{-46.2}$$ , $$265.7\pm 8.0$$ , $$487.6\pm 19.2$$ ) MeV with Gaussian and power-law wave functions, respectively, while we have $$f_{D_{2}^{*},D_{s2}^{*},B^{*}_{2},B^{*}_{s2}}$$ = ( $$143.6^{+24.9}_{-21.8}$$ , $$209.5^{+29.1}_{-24.2}$$ , $$80.9^{+33.8}_{-27.7}$$ , $$109.7^{+15.7}_{-15.0}$$ ) MeV with only Gaussian wave functions.

Variational analysis of mass spectra and decay constants for ground state pseudoscalar and vector mesons in the light-front quark model

Using the variational principle, we compute mass spectra and decay constants of ground state pseudoscalar and vector mesons in the light-front quark model (LFQM) with the QCD-motivated effective Hamiltonian including the hyperfine interaction. By smearing out the Dirac delta function in the hyperfine interaction, we avoid the issue of negative infinity in applying the variational principle to the computation of meson mass spectra and provide analytic expressions for the meson mass spectra. Our analysis with the smeared hyperfine interaction indicates that the interaction for the heavy meson sector including the bottom and charm quarks gets more point-like. We also consider the flavor mixing effect in our analysis and determine the mixing angles from the mass spectra of $(\omega,\phi)$ and $(\eta,\eta')$. Our variational analysis with the trial wave function including the two lowest order harmonic oscillator basis functions appears to improve the agreement with the data of meson decay constants and the heavy meson mass spectra over the previous computation handling the hyperfine interaction as perturbation.

Heavy vector and axial-vector mesons in hot and dense asymmetric strange hadronic matter

We calculate the effects of finite density and temperature of isospin asymmetric strange hadronic matter, for different strangeness fractions, on the in-medium properties of vector $\left( D^{\ast}, D_{s}^{\ast}, B^{\ast}, B_{s}^{\ast}\right)$ and axial-vector $\left( D_{1}, D_{1s}, B_{1}, B_{1s}\right)$ mesons, using chiral hadronic SU(3) model and QCD sum rules. We focus on the evaluation of in-medium mass-shift and shift in decay constant of above vector and axial-vector mesons. In QCD sum rule approach, the properties, e.g., the masses and decay constants of vector and axial-vector mesons are written in terms of quark and gluon condensates. These quark and gluon condensates are evaluated in the present work within chiral SU(3) model, through the medium modification of, scalar-isoscalar fields $\sigma$ and $\zeta$, the scalar-isovector field $\delta$ and scalar dilaton field $\chi$, in the strange hadronic medium which includes both nucleons as well as hyperons. As we shall see in detail, the masses and decay constants of heavy vector and axial-vector mesons are affected significantly due to isospin asymmetry and strangeness fraction of the medium and these modifications may influence the experimental observables produced in heavy ion collision experiments. The results of present investigations of in-medium properties of vector and axial-vector mesons at finite density and temperature of strange hadronic medium may be helpful for understanding the experimental data from heavy-ion collision experiments in-particular for the Compressed Baryonic Matter (CBM) experiment of FAIR facility at GSI, Germany.

Accurate decay-constant ratiosfB*/fBandfBs*/fBsfrom Borel QCD sum rules

We present our analysis of the decay constants of the beauty vector mesons $B^*$ and $B^*_s$ within the framework of dispersive sum rules for the two-point correlator of vector currents in QCD. While the decay constants of the vector mesons $f_{B^*}$ and $f_{B_s^*}$ $-$ similar to the decay constants of the pseudoscalar mesons $f_B$ and $f_{B_s}$ $-$ individually have large uncertainties induced by theory parameters not known with a satisfactory precision, these uncertainties almost entirely cancel out in the ratios of vector over pseudoscalar decay constants. These ratios may be thus predicted with very high accuracy due to the good control over the systematic uncertainties of the decay constants gained upon application of our hadron-parameter extraction algorithm. Our final results read $f_{B^*}/f_B=0.944\pm0.011_{\rm OPE}\pm0.018_{\rm syst}$ and $f_{B_s^*}/f_{B_s}=0.947\pm0.023_{\rm OPE}\pm0.020_{\rm syst}$. Thus, both $f_{B^*}/f_B$ and $f_{B_s^*}/f_{B_s}$ are less than unity at 2.5$\sigma$ and 2$\sigma$ level, respectively.

Spectroscopy of SU(4) gauge theory with two flavors of sextet fermions

We present a first look at the spectroscopy of SU(4) gauge theory coupled to two flavors of Dirac fermions in the two-index antisymmetric representation, which is a real representation. We compute meson and diquark masses, the pseudoscalar and vector meson decay constants, and the masses of six-quark baryons. We make comparisons with large-Nc expectations.

Erratum: Decay constants of heavy-light vector mesons from QCD sum rules [Phys. Rev. D88, 014015 (2013)

Erratum: Decay constants of heavy-light vector mesons from QCD sum rules [Phys. Rev. D<b>88</b>, 014015 (2013)