In this article, we calculate the strong coupling constant $g$ among the decuplet baryons, the octet baryons and the pseudoscalar mesons in the heavy baryon chiral perturbation theory with the light-cone QCD sum rules, and study the strong decays $Σ^* \to Λπ,Σπ$. The numerical value of the strong coupling constant $g$ is consistent with our previous calculation, the central values lead to small SU(3) breaking effects, less than 6%; and no definitive conclusion can be drawn due to the large uncertainties.
For purely leptonic decays of pseudoscalar mesons, the decay rates are related to the product of the relevant weak interaction-based CKM matrix element of the constituent quarks on the one hand, and the strong interaction parameter, the decay constant, which is related to the overlap of the quark and antiquark in the meson on the other hand. The decay constants for these mesons can thus be estimated from the decay rates of the respective dominant decay modes. The decay constants so obtained are used to estimate the decay rates of the less dominant modes, which are in good agreement with experi…
The leptonic decay constant of the pseudoscalar mesons a calculated by use of the relativistic constituent quark model constructed on the point form of Poincare-covariant quantum mechanics. We discuss the role relativistic corrections for decay constants of pseudoscalar mesons with heavy quarks. We consider the heavy mass limit of decay constant for two-particle system with equal masses.
We calculate the decay constant of $D_s$ and $D_s^{*}$ with $\bar{B}^0 \ra D^{+}\ell^{-}ν$ and $\bar{B}^0 \ra D^{+}D_s^{-(*)}$ decays. In our analysis we assume that factorization ansatz works and used two different form factor behaviours (constant and monopole-type) for $F_0(q^2)$. We also consider the QCD-penguin contributions in hadronic decays within the NDR renormalization scheme at NLO calculation. We estimate the decay constant of the $D_s$ meson to be $219\pm46 MeV$ for (pole/pole)-type form factor and $239\pm50$ $MeV$ for (pole/constant)-type form factor. For $D_s^{*}$ meson, we predi…
We calculate the mass and decay constant of the $D_2^*(2460)$ tensor meson in the framework of QCD sum rules. The obtained result on the mass is compatible with the experimental data. Our prediction on the decay constant can be checked in experiment.
Decay constant of eta-meson f is calculated on the basis of the QCD sum rule method. An instanton contribution is taken into account. The result is f = 0.17 GeV.
We investigate decay constants of P and D-wave heavy-light mesons within the mock-meson approach. Numerical estimates are obtained using the relativistic quark model. We also comment on recent calculations of heavy-light pseudo-scalar and vector decay constants.
Strong decay constants of the heavy tensor to heavy pseudoscalar (vector) and light pseudoscalar mesons are estimated within the light cone QCD sum rules. It is obtained that the values of these coupling constants are very strongly dependent on the choice of the Lorentz structure. Moreover, using these strong coupling constants the corresponding decay widths are calculated.
With the decay constants of $D$ and $D_s$ mesons measured in experiment recently, we revisit the study of the bound states of quark and antiquark in $B$ and $D$ mesons in the relativistic potential model. The relativistic bound state wave equation is solved numerically. The masses, decay constants and wave functions of $B$ and $D$ mesons are obtained. Both the masses and decay constants obtained here can be consistent with the experimental data. The wave functions can be used in the study of $B$ and $D$ meson decays.
We present the outcomes of a very recent investigation of the decay constants of nonstrange and strange heavy-light beauty vector mesons, with special emphasis on the ratio of any such decay constant to the decay constant of the corresponding pseudoscalar meson, by means of Borel-transformed QCD sum rules. Our results suggest that both these ratios are below unity.
The mass and decay constant of the ground state strange tensor meson $K_2^*(1430)$ with $I(J^P)=1/2(2^+)$ is calculated using the QCD sum rules method. The results are consistent with the experimental data. It is found that SU(3) symmetry breaking effect constitutes about $20^0/_0$ of the decay constant.
The relativistic quark potential model (QPM) is developed for describingvector mesons and their leptonic decays. The new representation Salpeter equation for vector mesons is proposed. Studying the $τ\toρν$ decay theexpression for $ρ$-meson leptonic decay constant $f_ρ$ isobtained. It is shown that quark model describes on a satisfactory level both theconstant $f_ρ$ and the masses of other charged vector mesons. Thevalues for the leptonic decay constants of $K^{*},D^{*},D^{*}_s,B^{*},B^{*}_c$ mesons are predicted.
For tetraquarks of the form $T[(\bar{Q}q)(Q\bar{q})]$ we give sum rules for their decay coupling constants, taking into account the SU(3) symmetry breaking interactions to first order.
Within the independent-harmonic-oscillator model for quarks inside a hadron, a rigorous method is presented for the calculation of coupling constants and transition potentials for hadronic decay, as needed in a multi-channel description of mesons.
We calculate the leading quark mass corrections of order $m_q\log(m_q)$, $m_q$ and $m_q^{3/2}$ to the vector meson decay constants within Heavy Vector Meson Chiral Perturbation Theory. We discuss the issue of electromagnetic gauge invariance and the heavy mass expansion. Reasonably good fits to the observed decay constants are obtained.
We examine the compatibility in predicted masses and the decay constants of $D^{*}_{sJ}$ mesons in terms of two-quark contents. We find that the results of a specific model, which is governed by heavy quark limit, will encounter a challenge to fit both spectra and decay constants simultaneously.
We focus on the chiral and heavy quark mass expansion of mesons masses and decay constants. We propose a light-front QCD formalism for the evaluation of these quantities, consistent with chiral perturbation theory and heavy quark effective theory.
An update is given of the determination of leptonic decay constants of charm and beauty mesons in the framework of relativistic Hilbert moments and Laplace transform QCD sum rules.
We use a covariant supermultiplet theory to determine the primary coupling constant associated with several types of two-body meson decay. Despite the diverse range of decays considered the primary coupling constant is surprisingly uniform. We envisage the extension of the techniques to heavy quark cases, including as preliminary examples the calculation of the $D^{*+}$ and $D^{*0}$ total decay widths with results $57.7 \pm 1.5$ KeV and $42.5 \pm 2.6$ KeV respectively, as well as some predictions about $D^*$ and $B^*$ radiative decays. (3 uuencoded Postscript Files are appended at the end of t…
We evaluate the decay constants for the B and $D$ mesons and the form factors for the semileptonic decays of the B meson to $D$ and $D^*$ mesons in a Bethe-Salpeter model. From data we extract $V_{cb}=0.039 \pm 0.002$ from ${\bar B} \to D^* l {\barν} $ and $V_{cb}=0.037 \pm 0.004$ from ${\bar B} \to D l {\barν} $ decays. The form factors are then used to obtain non-leptonic decay partial widths for $ B\to D π(K) $ and $B \to D D (D_s) $ in the factorization approximation.
A new framework of heavy quark effective field theory (HQEFT) is studied and compared with the usual heavy quark effective theory (HQET). $|V_{ub}|$, $|V_{cb}|$ and heavy meson decay constants are extracted in the new framework. HQEFT can yield reasonable results for both exclusive and inclusive decays.
We calculate the masses and decay constants of the light tensor mesons with quantum numbers $J^P =2^+$ in the framework of the QCD sum rules in the standard model. The non-perturbative contributions up to dimension-$5$ as important terms of the operator product expansion are considered.
We propose a method to determine the leptonic decay constant $f_{B^*}$ in the infinite heavy quark mass limit from the analysis of the radiative decay mode $B^- \to \ell^- {\bar ν}_\ell γ$. The method relies on HQET symmetries and on experimental data from $D^{*0} \to D^0 γ$.
The decay constants of the low lying S-wave $B_c$ mesons, i.e. $B_c(nS)$ and $B^*_c(nS)$ with $n\leq 3$, are calculated in the nonrelativistic quark model. The running coupling of the strong interaction is taken into account, and the uncertainties due to varying parameters and losing Lorentz covariance are considered carefully. As a byproduct, the decay constants of the low lying S-wave charmonium and bottomium states are given in the appendixes.
The recently developed 'Resummed' ChPT is illustrated on the case of pseudoscalar meson decay constants. We try to get an estimate of the eta decay constant, which is not well known from experiments, while using several ways including the Generalized ChPT Lagrangian to gather information beyond Standard next-to-leading order. We compare the results to published ChPT predictions, our own Standard ChPT calculations and available phenomenological estimates.
In the present work, $D_{s}$ and $B_{s}$ meson parameters are investigated in the framework of thermal QCD sum rules. The temperature dependence of the mass and the leptonic decay constants are investigated by using Borel transform sum rules and Hilbert moment sum rules. To increase sensitivity, the vacuum contributions are subtracted from thermal expressions and the temperature dependences of the leptonic decay constants and meson masses are studied.
We calculate the decay constants of $D_s$ and $D_s^{*}$ with $\bar{B}^0 \ra D^{+}\ell^{-}ν$ and $\bar{B}^0 \ra D^{+}D_s^{-(*)}$ decays. In our analysis we take the factorization method including non-factorizable term contributions and used two different form factor behaviours (constant and monopole-type) for $F_0(q^2)$. We also consider the QCD-penguin and Electroweak-penguin contributions in hadronic decays within the NDR renormalization scheme at NLO calculation. We estimate the decay constant of the $D_s$ meson to be $233\pm49$ ${\rm MeV}$ for (pole/pole)-type form factor and $255\pm54$ ${\…
The decay constant of the $η$-meson in the framework of 'resummed' chiral perturbation theory is discussed. A theoretical prediction is compared to the available determinations. Compatibility of these determinations with the latest fits of the SU(3) low energy coupling constants is investigated. Preliminary results for the obtained constraints on the low energy coupling constants $L^r_5$ and $L^r_4$, using Bayesian statistical approach, are presented.
Novel relativistic expressions are used to calculate the weak decay constants of pseudoscalar and vector mesons within the constituent quark model. Meson wave functions satisfy the quasipotential equation with the complete relativistic potential. New contributions, coming from the negative-energy quark states, are substantial for the light mesons, significantly decrease the values of their decay constants and, thus, bring them into agreement with experiment. For heavy-light mesons these contribution are much less pronounced, but permit to reduce uncertainties of the predicted decay constants. …
We investigate the magnetic dipole decays $V\to Pγ$ of various heavy-flavored mesons such as $(D,D^*,D_s,D^{*}_s,η_c, J/ψ)$ and $(B,B^*,B_s,B^*_s,η_b,Υ)$ using the light-front quark model constrained by the variational principle for the QCD-motivated effective Hamiltonian. The momentum dependent form factors $F_{VP}(q^2)$ for $V\to Pγ^*$ decays are obtained in the $q^+=0$ frame and then analytically continued to the timelike region by changing ${\bf q}_\perp$ to $i{\bf q}_\perp$ in the form factors. The coupling constant $g_{VPγ}$ for real photon case is then obtained in the limit as $q^2\to 0…
Using an effective Lagrangian approach based on heavy quark symmetry and chiral dynamics, we explore the strong decay widths and branching ratios of various resonances and suggest their JP find the coupling constants involved in the strong decays through pseudoscalar mesons. The present work also discusses about the possible spin-parity assignments of recently observed states by LHCb collaboration.
We calculate the pion decay constant near the critical temperature of the $O(N)$ nonlinear sigma model in the large $N$ limit. Making use of the known low temperature behavior, we construct a Padé approximant to obtain the behavior of $f_π(T)$ at all temperatures.
We study the radiative decay $ϕ\toπ^{0}π^{0}γ$ within the framework of a phenomenological approach in which the contributions of $σ$-meson, $ρ$-meson and $f_0$-meson are considered. We analyze the interference effects between different contributions and utilizing the experimental branching ratio for this decay we estimate the coupling constant $g_{ϕσγ}$.
We discuss the light-front zero-mode issue in the light-front quark model (LFQM) prediction of a vector meson decay constant from the perspective of the vacuum fluctuation consistent with the chiral symmetry of QCD. We extend the exactly solvable manifestly covariant Bethe-Salpeter model calculation to the more phenomenologically accessible realistic LFQM and present a self-consistent covariant description of the vector meson decay constant analyzing the twist-2 and twist-3 quark-antiquark distribution amplitudes with even chirality.
We estimate the decay constants $f_π$ and $f_K$ of the light mesons within a relativistic quantum-field model of interacting quarks and gluons confined analytically. The necessary physical parameters, the quark masses $m_u$ and $m_s$, the coupling constant $α_s$ and the confinement scale $Λ$ have been obtained from our previous investigation on the meson ground states, orbital and radial excitations by using the ladder Bethe-Salpeter equation. Our approach provides a solid framework to compute the meson spectra, the lowest glueball state and decay constants of pseudoscalar mesons (as well as o…
The matrix element \Vud of the CKM matrix can be determined by two independent measurements in neutron decay: the neutron lifetime $τ_n$ and the ratio of coupling constants $λ=g_A/g_V$, which is most precisely determined by measurements of the beta asymmetry angular correlation coefficient~$A$. We present recent progress on the determination of these coupling constants.
Masses and decay constants of mesons containing a single $c$ or $b$ quark are described within the framework of heavy-quark symmetry. The $B_s^* - B_s$ and $\bar B^{*0} - \bar B^0$ mass splittings are found equal to within a fraction of an MeV. Decay constants of $D$ and $B$ mesons are estimated using isospin mass splittings in the $D$, $D^*$, $B$, and $B^*$ states to isolate the electromagnetic hyperfine interaction between quarks. A relation following from the use of splittings in kaons is also considered.
We present the next-to-next-to-leading order (NNLO) QCD corrections to the decay constants for both the pseudoscalar and vector beauty-charmed mesons $B_{c}$ and $B^*_{c}$ in nonrelativistic QCD effective theory. Explicit NNLO calculation verified that the $B_c$ decay constant from pseudoscalar current is identical with the $B_c$ decay constant from axial-vector current. The NNLO result for the vector decay constant of $B^*_{c}$ meson is novel. Combined with the latest extraction of nonrelativistic QCD long-distance matrix elements of $B_c$ meson, we give the branching ratios of leptonic decay…
We establish irrational constants, that contribute to the positronium lifetime at $O(α)$ and $O(α^2)$ order. In particular we show, that a new type of constants appear, which are not related to Euler--Zagier sums or multiple $ζ$ values.
We calculate finite mass corrections to leptonic decay constants in HQET using QCD sum rules. The results are given to two--loop accuracy including renormalization group analysis. The contribution of unknown two--loop anomalous dimension matrix--elements is estimated. We find that the $1/m_Q$ corrections to $f_P$, the decay constant of a pseudoscalar meson, amount $-(23\pm4\pm2)\%$ for the B meson. The first error comes from the sum rule uncertainty, the second one from unknown or not accurately known matrix elements in HQET. We obtain a ratio of vector to pseudoscalar decay constant of $1.00\…
The pion decay constant f_pi plays a crucial role in many areas of low energy particle physics. Its value may e.g. be deduced from experimental data on leptonic pion decays. Here, we provide comments on several aspects of this evaluation. In particular, we point out that at the present level of experimental accuracy, the value of f_pi is sensitive to the value of the pion mass chosen in its chiral expansion.
The mass and decay constant of the ground state of spin singlet $b \bar{b}$ is calculated by using the QCD sum rules method. This meson is an axial vector $P$-wave named $h_b(1P)$ meson with $J^P =1^+$. It is found that the mass of this meson is $(m=9940\pm 37)$ MeV, which is consistent with the recent experimental data by Belle collaboration.
Several methods exist to measure $CP$ violation observables related to the $C\!K\!M$ angle $γ$. These observables are different for every $B$ meson decay channel. However, the information they contain on $γ$ is encoded in a similar way for all of them. This paper describes a strategy for a simultaneous measurement including several $B$ meson decay channels, while taking into account any possible correlations between them.
A relativistic constituent quark model is adopted to give an unified description of the leptonic and semileptonic decays of pseudoscalar mesons (π, K, D, D_s, B, B_s). The calculated leptonic decay constants and form factors are found to be in good agreement with available experimental data and the results of other approaches. Eventually, the model is found to reproduce the scaling behaviours of spin-flavor symmetry in the heavy-quark limit.
The relative magnitude of the decay constants of the pseudoscalar and vector beauty mesons poses (in contrast to the case of charmed mesons) a long-standing puzzle. We revisit this problem within the framework of our recent improvements of the QCD sum-rule formalism for relating observable properties of mesons to quantum chromodynamics and are led to conclude that the decay constants of the beauty vector mesons are undoubtedly smaller than those of their pseudoscalar counterparts.
Decay constants of $P$-wave mesons are computed in the framework of instantaneous Bethe-Salpeter method (Salpeter method). By analyzing the parity and possible charge conjugation parity, we give the relativistic configurations of wave functions with definite parity and possible charge conjugation parity. With these wave functions as input, the full Salpeter equations for different $P$-wave states are solved, and the mass spectra as well as the numerical values of wave functions are obtained. Finally we compute the leptonic decay constants of heavy-heavy and heavy-light $^3P_0$, $^3P_1$ and $^1…
We compute the decoupling function of the MSbar renormalized fine-structure constant up to four-loop order in perturbative QCD. The results are used in order to determine the related top-quark contributions to the Higgs-boson decay into two photons in the heavy top-quark mass limit to order alpha_s^4.
Non-leptonic decays of B mesons into two mesons or meson resonances are studied on the basis of two versions of simple pole-dominance models involving scalar, vector, pseudoscalar and axial-vector poles. The results are compared with those obtained from the usual factorization model and used to obtain information on strong coupling constants between B meson and one light or one charmed meson, respectively. These coupling constants are compared to results from various QCD sum rule calculations.
Sum rules for exclusive production of heavy meson pairs in $e^+e^-$ annihilation are used to evaluate the $Υ(4S) \to B \bar B$ and $ψ(3770) \to D \bar D$ decay widths. Infinitely heavy quark limit is discussed, so that scaling law for the quarkonium-meson coupling constant is derived. A value of the $B\bar B$ pair contribution into the leptonic constant $f_{Υ(4S)}$ is estimated.
Determination of the wave-function is very essential in the calculation of static and dynamic properties like masses,decay constants of pseudo-scalar mesons and masses of vector mesons.We use Dalgarno's perturbation theory and Variation-ally Improved Perturbation Theory (VIPT) to solve Schrodinger equation in a QCD inspired potential model wuth Cornell potential,which consists linear and coulomb potential.We use both the options like Columbic parent firstly and then linear parent while using the VIPT method. Comparison of both these methods and also with experimental results are done in the ca…
In this article, we calculate the contributions of the vacuum condensates up to dimension-6 in the operator product expansion, study the masses and decay constants of the heavy tensor mesons $D_2^*(2460)$, $D_{s2}^*(2573)$, $B_2^*(5747)$, $B_{s2}^*(5840)$ using the QCD sum rules. The predicted masses are in excellent agreement with the experimental data, while the ratios of the decay constants $\frac{f_{D_{s2}^*}}{f_{D_{2}^*}}\approx\frac{f_{B_{s2}^*}}{f_{B_{2}^*}}\approx\frac{f_{D_{s}}}{f_{D}}\mid_{\rm exp}$, where the exp denotes the experimental value.
Quenched chiral perturbation is used to study the decay constants for heavy-light mesons beyond the leading order in 1/M. The results are used to estimate the error in quenched lattice calculations of the decay constants. For the double ratio $R_1 = ( f_{D_s}/f_D) / (f_{B_s}/f_B)$ we find that the error is small, conservatively 6%, but likely smaller. We also find that quenching decreases the ratio $f_{D_s}/f_D$ relative to the unquenched theory.
The determination of the numerical value for the strong coupling constant from tau decays in perturbative QCD is briefly described. Main emphasis is made on the use of the renormalization scheme invariance of the theory for reducing uncertainties related to truncation of the series in the strong coupling constant. The analysis of the convergence of the series is presented and the possibility of the asymptotic growth at the NNNLO is discussed.
The procedure to calculate masses and matrix-elements in the presence of mixing of the basis states is explained in detail. We then apply this procedure to the two-loop calculation in Chiral Perturbation Theory of pseudoscalar masses and decay constants including quark mass isospin breaking. These results are used to update our analysis of $K_{\ell4}$ done previously and obtain a value of $m_u/m_d$ in addition to values for the low-energy-constants $L_i^r$.
We employ the framework of Bethe-Salpeter equation under Covariant Instantaneous Ansatz to study the leptonic decays of pseudoscalar mesons. The Dirac structure of hadron-quark vertex function $Γ$ is generalized to include various Dirac covariants besides $γ_5 $ from their complete set. The covariants are incorporated in accordance with a power counting rule, order by order in powers of the inverse of the meson mass. The decay constants are calculated with the incorporation of leading order covariants. Most of the results are dramatically improved.
We study the three-body baryonic B decay $\bar{B}^{0}_{s}\rightarrow p\barΛ K^{-}$ within the framework of the pole model via the baryonic $Λ_{b}$ pole. In our calculation, we require the strong coupling constant $g_{Λ_{b}B_{s}Λ}$ and investigate if $g_{Λ_{b}B_{s}Λ}=10.49\pm1.57$ is adopted, the branching ratio agrees with the experimental result, reported by the LHCb collaboration.
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 predicte…
We study the decay constants of pseudoscalar and vector $B$ meson in the framework of light-cone quark model (LCQM). We apply the variational method to the relativistic Hamiltonian with the Gaussian-type trial wave function to obtain the values of $β$ (scale parameter). Then with the help of known values of constituent quark masses, we obtain the numerical results for the decay constants $f_P$ and $f_V$, respectively. We compare our numerical results with the existing experimental data.
