The investigation in the work of the reaction electron-positron to omega and pi0 mesons in the 3P0 nonrelativistic quark model reveals that the reaction electron-positron to omega and pi0 mesons process at the energy region from the omega and pi mesons threshold to 2.0 GeV is dominated by the two-step process in which the primary quark-antiquark pair first forms rho and rho' mesons and then the vector mesons decay into omega and pi. With rho(1450) and rho(1700) mainly in 2S and 1D states respectively, the experimental data for the cross section of the reaction electron-positron to omega and pi0 mesons are well produced in the 3P0 quark model. The work supports the argument that rho(1450) is mainly a 2S meson and rho(1700) a 1D meson.
The branching ratios and photon spectra of the rare processes rho(omega)-> pi^0 pi^0 gamma, rho(omega) -> eta pi^0 gamma are calculated in the framework of the standard local quark Nambu--Jona-Lasinio (NJL) model. Three types of diagrams are considered: the quark box and the pole diagrams with scalar (sigma,a_0(980)) and vector (rho,omega) mesons. The obtained estimations for the widths of the processes rho(omega)-> pi^0 pi^0 gamma are in satisfactory agreement with existing experimental data. Predictions are made for the widths of the processes rho(omega) -> eta pi^0 gamma.
Two-photon decays of rho and omega mesons and strong decays rho -> eta pi and omega -> pi pi are described in the quark Nambu-Jona-Lasinio(NJL) model in dense medium. Decays of rho-meson are especially interesting because they contain intermediate a_0-meson which became a sharp resonance in the vicinity of phase transition of hadron matter into quark-gluon plasma. This leads to increasing rho decay width and, as a result, two-photon decay of rho-meson in medium became comparable with two-photon decays of scalar and pseudoscalar mesons in vacuum. Similar effect take place in the strong decay rh…
We evaluate the omega to rho pi transition and the omega to 3 pi decay using a Quark Level Linear Sigma Model ($QLσM$). We obtain $g^{QLσM}_{ωρπ}= (10.33 - 14.75) GeV^{-1}$ to be compared with other model dependent estimates averaging to $g_{ωρπ} = 16 GeV^{-1}$. We show that in the $QLσM$ a contact term is generated for the $ω\to 3 π$ decay. Although the contact contribution by itself is small, the interference effects turn out to be important.
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.
Simple quark models for the low lying vector mesons suggest a mixing between the u- and d-flavors and a violation of the isospin symmetry for the rho-omega system much stronger than observed. It is shown that the chiral dynamics, especially the QCD anomaly, is responsible for a restoration of the isospin symmetry in the rho-omega system.
We examine the radiative omega pi0etagamma and rho pi0etagamma decays in a phenomenological framework. We consider the VMD mechanism, chiral loops, intermediate a0-meson and rho−omega mixing. We find the values of the decay width coming from the different amplitudes and compare the results with other studies. We observe that a0-meson intermediate state is very important in the case of the rho pi0etagamma decay and small in the other case for which VMD contribution is dominant.
A chiral SU(2) x SU(2) Lagrangian containing, besides the usual meson fields, their first radial excitations is considered. The Lagrangian is derived by bosonization of the Nambu-Jona-Lasinio quark model with separable non-local interactions, with form factors corresponding to 3-dimensional ground and excited state wave functions. The spontaneous breaking of chiral symmetry is governed by the NJL gap equation. The first radial excitations of the pions, rho-and omega-mesons are described with the help of two form factors. The weak decay constant F_pi' is calculated. The values for the decay wid…
We study possible contributions to the Ds^+ -> omega pi^+ and Ds^+ -> rho^0 pi^+ decay amplitudes. The Ds^+ -> omega pi^+ decay amplitude vanishes when the naive factorization is used, while the Ds^+ -> rho^0 pi^+ decay amplitude arises due to the annihilation contribution. We find that amplitudes for both decays might be a result of the internal K, K^* exchange. The Ds^+ -> omega pi^+ amplitude might obtain additional contribution from Ds^+ -> rho^0 eta (eta') re-scattering. The low experimental bound on the Ds^+ -> rho^0 pi^+ rate can be understood as a result of combination of the pi(1300) …
We predict differential decay distributions for phi->rho gamma gamma and phi -> omega gamma gamma using chiral perturbation theory. We also consider the isospin violating decay phi -> omega pi^0. Experimental information on these decays can be used to determine couplings in the heavy vector meson chiral Lagrangian.
Mass distributions of pi^+ pi^- pi^0 and omega pi^0 systems in the e^+ e^- annihilation obtained by the several experiments are analyzed. We obtain indication of light-vector mesons omega'(1.3) and rho'(1.3) in the lower mass region. Those states are expected to exist in the U~(12)-classification scheme.
A way to explain the puzzling difference between the pion form factor as measured in e+ e- annihilations and in tau decays is discussed. We show that isospin symmetry breaking, beside the already identified effects, produces also a full mixing between the rho0, omega and phi mesons which generates an isospin 0 component inside the rho0 meson. This effect, not accounted for in current treatments of the problem, seems able to account for the apparent mismatch between e+ e- and tau data below the phi mass.
We present a novel dynamics for generating sizable CP-violating asymmetries in the decays of charged $B^\mp\to π^\mp ω, π^\mpρ^0, π^0ρ^\mp$, and in $\bar{B^0}(B^0)\toπ^\mpρ^\pm$. The dynamics for the necessary final-state interactions involves the mixing of G-parity eigenstates of the system $(\bar{D}^*D,D^*\ol{D})$ with the $G=\pm 1$ states of $πω$ and $πρ$, respectively. The dynamical effect is enhanced by the empirically large branching ratio for decays to $(\bar{D}^*D,D^*\bar{D})$. A correlated result is a markedly enhanced branching ratio for $\bar{B^0}(B^0)\toπ^0ρ^0$, which has now been …
In this paper we improve and extend a recent analysis which showed that the rho-omega mixing amplitude cannot be unambiguously extracted from the pion electromagnetic form-factor in a model independent way. In particular, we focus on the argument that the extraction is sensitive to the presence of any intrinsic omega_I -> pi pi coupling. Our extended analysis confirms the original conclusion, with only minor, quantitative differences. The extracted mixing amplitude is shown to be sensitive to both the intrinsic coupling omega_I -> pi pi and to the value assumed for the mass of the rho^0-meson.
The radiative B-> rho gamma, B-> omega gamma decay modes are caused by the FCNC process, so they give us good insight towards probing the standard model in order to search for new physics. In this paper, we compute the branching ratio, direct CP asymmetry, and isospin breaking effects using the perturbative QCD approach within the standard model.
We evaluate the decays B => K* pi, K (rho,omega,phi) adding the long distance charming penguin contributions to the short distance: Tree+Penguin amplitudes. We estimate the imaginary part of the charming penguin by an effective field theory inspired by the Heavy Quark Effective Theory and parameterize its real part. The final results for branching ratios depend on only two real parameters and show a significant role of the charming penguins. The overall agreement with the available experimental data is satisfactory.
In order to calculate the rho - omega mixing we extend the chiral couplings of the low-lying vector mesons in chiral perturbation theory to a lagrangian that contains two vector fields. We determine the momentum dependence of the two-point function and recover an earlier result for the on-shell expression. We discuss the off-shell behaviour of the mixing.
We update our analysis of rho-omega mixing effects in the pion form factor to incorporate the recently published BaBar e^+e^- --> pi^+π^- cross-sections. The implications for tau-decay-based Standard Model estimates of the leading order hadronic contribution [a_μ]_{had}^{LO}, to the anomalous magnetic moment of the muon, and for the extraction of the off-diagonal vector meson self-energy matrix element, Pi_{ρω}(m_ρ^2), are discussed.
We study the implications of several recent high-precision measurements of the pion form factor in the region of the rho-omega interference "shoulder" for (i) the extraction of the rho-omega mixing matrix element, Pi_{ρω}(m_rho^2), and (ii) the evaluation of the isospin-breaking (IB) correction needed to incorporate hadronic tau decay data into the determination of the Standard Model expectation for the leading order hadronic contribution, [a_mu]_{had}^{LO}, to the anomalous magnetic moment of the muon, focussing, in the latter case, on the model-dependence of the rho-omega mixing component of…
Neglecting smaller amplitudes the time-dependent CP asymmetry in penguin-dominated b -> s q \bar q transitions (such as B -> phi K_S) is expected to equal sin(2 beta), an expectation not borne out by the present average experimental data. I compute and discuss the correction due to the smaller amplitudes in the framework of QCD factorization.
Based on coupling constants extracted from fitting various data, the selected branching ratios and full widths of rho', rho'', and omega', omega'' resonances are calculated, and some topics on the spectroscopy of these states are discussed.
Based on the previous and recent fits of multiple data on the reactions of e^+e^- annihilation, tau lepton decay, and the reaction K^-p -> pi^+pi^- Lambda, the magnitude of the branching ratios and total widths of the isovector rho', rho'', and the isoscalar omega', omega'' resonances are calculated. Some topics on the spectroscopy of the rho(1450) and omega(1420) states are discussed.
In an attempt to explain the latest experimental result about the branching ratio of $ω\to π^0π^0γ$ decay we reexamine the decay mechanism of this decay in a phenomenological framework in which the contributions of VMD, chiral loops, $σ$-meson intermediate state amplitudes and the effects of $ω-ρ$ mixing are considered. We conclude that in order to obtain the experimental value of the branching ratio $B(ω\to π^0π^0γ)$ $σ$-meson amplitude which makes a substantial contribution should be included into the reaction mechanism and the effects of $ω-ρ$ mixing should be taken into account. We also es…
Contributions of two-pseudoscalar and vector-pseudoscalar meson loops to the rho-omega mass splitting are evaluated in a covariant model based on studies of the Schwinger-Dyson equations of QCD. The role and importance of the different time orderings of the meson loops is analyzed and compared with those obtained within time-ordered perturbation theory. It is shown that each meson loop contributes less than 10% of the bare mass, and decreases as the masses of the intermediate mesons increase beyond approximately m_rho/2. A mass splitting of m_omega - m_rho ~= 25 MeV is obtained from the pi pi,…
Within a broad class of models we show that the amplitude for rho^0-omega mixing must vanish at the transition from timelike to spacelike four momentum. Hence in such models the mixing is either zero everywhere or is necessarily momentum-dependent. This lends support to the conclusions of other studies of rho-omega mixing and calls into question standard assumptions about the role of rho-omega mixing in the theoretical understanding of charge-symmetry breaking in nuclear systems.
Medium modifications of the pion-omega-rho vertex are analyzed in context of the omega -> pi gamma* and rho -> pi gamma* decays in nuclear matter. A relativistic hadronic model with mesons, nucleons, and Delta(1232)isobars is applied. A substantial increase of the widths for the decays omega -> pi gamma* and rho -> pi gamma* is found for photon virtualities in the range 0.3-0.6 GeV. This enhancement has a direct importance for the description of dilepton yields obtained in relativistic heavy-ion collisions.
We compare flavour singlet and non-singlet vector mesons from first principles using lattice QCD. With N_f=2 flavours of light quark, this addresses the omega-rho mass difference. Using maximally twisted-mass lattice QCD, we are able for the first time to determine this mass difference precisely and we compare with experiment. We also discuss omega-rho mixing effects arising within QCD through the u-d quark mass difference.
A method is proposed for the determination of the unitarity angle alpha through tree penguin interference. The modes needed would be of the form B0/B0-bar -> rho0 M and B0/B0-bar -> omega M where M is spin-0 uu-bar/dd-bar meson, for instance M=pi0, eta, eta',a0 or f0. An analogous method can also determine gamma using M=KS or K_L. The validity of the theoretical approximations used may be tested by over determining alpha with several modes. If two or more modes are used, the determination has a four-fold ambiguity but additional information from pure penguin decays or theoretical estimates may…
The extraction of CKM-matrix-element information from hadronic B-decays generally suffers from discrete ambiguities, hampering the diagnosis of physics beyond the Standard Model. We show that a measurement of the rate asymmetry, which is CP-violating, in $B^{\pm}\toρ^{\pm}ρ^0(ω)\toρ^{\pm}π^+π^-$, where the invariant mass of the $π^+π^-$ pair is in the vicinity of the $ω$ resonance, can remove the mod($π$) uncertainty in $α\equiv arg [-V_{td} V_{tb}^\ast/(V_{ud}V_{ub}^\ast)]$ present in standard analyses.
We investigate the splitting and mixing of $ρ$ and $ω$ mesons in nuclear matter. The calculations were performed on the basis of QCD sum rules and include all operators up to mass dimension-6 twist-4 and up to first order in the coupling constants. Special attention is devoted to the impact of the scalar 4-quark condensates on both effects. In nuclear matter the Landau damping governs the $ρ- ω$ mass splitting while the scalar 4-quark condensates govern the strenght of individual mass shifts. A strong in-medium mass splitting causes the disappearance of the $ρ- ω$ mixing.
The suggestion of momentum dependence in the amplitude for rho-omega mixing has generated concern over related implications for vector meson dominance and the photon-rho coupling. We discuss two established representations of vector meson dominance and show that one of these is completely consistent with such a coupling. We then apply it to a calculation of the pion electromagnetic form-factor. Our analysis leads to a new value for the on-shell rho-omega mixing amplitude of (-3800 +/- 370) MeV^2.
It is shown, in a model independent way, that the large difference in rho and omega widths gives rise to a new source of momentum dependence for the rho-omega mixing matrix element. The q^2 dependence arising due to the meson widths leads to a significant alteration of the result obtained in the zero-width approximation usually discussed in the literature. The origin of this strong momentum dependence lies in the difference between the rho and omega meson widths.
In our past experiments on a single electron and positron we measured the cyclotron and spin-cyclotron difference frequencies omega_c and omega_a and the ratios a = omega_a/ omega_c at omega_c = 141 Ghz for e^- and e^+ and later, only for e^-, also at 164 Ghz. Here, we do extract from these data, as had not done before, a new and very different figure of merit for violation of CPT symmetry, one similar to the widely recognized impressive limit |m_Kaon - m_Antikaon|/m_Kaon < 10^-18 for the K-mesons composed of two quarks. That expression may be seen as comparing experimental relativistic masses…
We re-examine and extend a recent analysis which showed that the rho-omega mixing amplitude cannot be unambiguously extracted from the pion electromagnetic form-factor in a model independent way. In particular, we focus on the argument that the extraction is sensitive to the presence of any intrinsic omega_I -> 2pi coupling. Our extended analysis confirms the original conclusion, with only minor, quantitative differences. The extracted mixing amplitude is shown to be sensitive to both the intrinsic coupling omega_I -> 2pi and to the value assumed for the mass of the neutral rho meson.
We study composite systems of light ($ρ$ and $ω$) and heavy ($D^*$) vector mesons by using the interaction within the hidden gauge formalism. We find a strong attraction in the isospin, spin channels $(I,S)=(1/2,0)$; $(1/2,1)$; $(1/2,2)$ with positive parity. The attraction is large enough to strongly bind these mesons in states with these quantum numbers, leading to states which can be identified with $D_2^*(2460)$ and probably with $D^*(2640)$, the last one without experimental spin and parity assignment. In the case of $I=3/2$ one obtains repulsion and thus, no exotic mesons in this sector …
The topic of rho-omega mixing has received renewed interest in recent years and has been studied using a variety of modern techniques. A brief history of the subject is presented before summarising recent developments in the field. The present status of our understanding is discussed.
The excitation curve of e+e- annihilation into four charged pions in the rho(770) region is calculated using three existing models with rho mesons and pions in intermediate states supplemented by Feynman diagrams with the a_1(1260)pi intermediate states. A two-term phenomenological Lagrangian of the a_1-rho-pi interaction is used. The mixing angle is determined by fitting the e+e- --> pi+pi-pi+pi- cross section data of the Novosibirsk CMD-2 collaboration and also its combination with the low-energy part of the BaBar collaboration data. It is shown that the inclusion of the a_1-pi intermediate …
A novel mechanism for $ρ-ω$ mixing induced by neutron-proton asymmetry in nuclear matter is uncovered and the variation of the mixing angle with the extent of asymmetry is presented.
We re-analyse the two- and three-pion mass distributions in the decays X(3872)->rho J/psi and X(3872)->omega J/psi and argue that the present data favour the 1++ assignment for the quantum numbers of the X.
We extend the "hard wall" gravity dual of QCD by including tensor fields b_{MN} that correspond to the QCD quark bilinear operators qbar sigma^{mu nu} q. These fields give rise to a spectrum of states which include the h_1 and b_1 mesons, as well as a tower of excited omega/rho meson states. We also identify the lowest-dimension term which leads to mixing between the new rho states and the usual tower of rho mesons when chiral symmetry is broken.
The formalism underlying the analysis of e+e- -> pi+pi- in the rho-omega interference region is carefully revisited. We show that the standard neglect of the pure I=0 omega, omega_I, `direct'' coupling to pi-pi is not valid, and extract those combinations of the direct coupling and ρ-omega mixing allowed by experiment. The latter is shown to be only very weakly constrained by experiment, and we conclude that data from the e+e- -> pi+pi- interference region cannot be used to fix the value of rho-omega mixing in a model-independent way unless the errors on the experimental phase can be significa…
We present an improved calculation of $B\to$ light vector form factors from light-cone sum rules, including one-loop radiative corrections to twist-2 and twist-3 contributions, and leading order twist-4 corrections. The total theoretical uncertainty of our results at zero momentum transfer is typically 10% and can be improved, at least in part, by reducing the uncertainty of hadronic input parameters. We present our results in a way which details the dependence of the form factors on these parameters and facilitates the incorporation of future updates of their values from e.g. lattice calculat…
Based on the analysis of both Borel and Finite-Energy QCD sum rules, the inclusion of finite mesonic widths leads to a dramatic effect on the predictions for the momentum dependence of the rho-omega mixing matrix element. It is shown that the rho-omega mixing matrix element traditionally discussed in the literature, has the same sign and similar magnitude in the space-like region as its on-shell value. This contrasts the zero-width result where the mixing matrix element is typically of opposite sign in the space-like region.
We present a detailed study of direct CP violation and branching ratios in the channels $B^{0,\pm} \to π^{+}π^{-} V^{0,\pm}$, where $V$ is a vector meson ($K^{* 0,\pm}$ or $ρ^{\pm}$). Emphasis is placed upon the important role played by ${ρ^{0}}-ω$ mixing effects in the estimation of the CP-violating asymmetry parameter, $a_{cp}$, associated with the difference of $B$ and $\bar B$ decay amplitudes. A thorough study of the helicity amplitudes is presented as a function of the pion-pion invariant mass. All of the calculations and simulations considered correspond to channels which will be analyz…
We review the current status of rho-omega mixing and discuss its implication for our understanding of charge-symmetry breaking. In order to place this work in context we also review the photon-hadron coupling within the framework of vector meson dominance. This leads naturally to a discussion of the electromagnetic form-factor of the pion and of nuclear shadowing.
We study the self-energy amplitudes for the rho-omega meson system produced by an effective field theory model at the quark level characterized by a finite range quark-quark interaction and an isospin breaking bare quark mass difference $m_u - m_d$. Dynamical effects associated with confinement and dressing of quarks and the finite size of the produced $\bar{q}q$ meson modes are treated. Parameters of this approach, previously constrained by soft pion physics, are here supplemented in a minimal way to reproduce $m_ω$ and $g_{ρππ}$. Calculations are carried out up to the one pion loop level and…
Second-class weak currents can in the standard model be induced by chiral symmetry breaking. In the specific case of the decay tau-->omega pi nu_tau, dominated by the first-class vector current with the rho quantum numbers, such effects would manifest themselves by small axial vector (or, generally, non-vector) contributions to the decay rate. We present an attempt to estimate such effects, based on a vector and axial-vector dominance model of the relevant matrix elements supplemented by omega-rho mixing. We also give an indication on the amplitude directly mediated by b_1(1235)-->omega pi, in…
We extract the G-parity-violating branching ratio Br(omega->pi^+ pi^-) from the effective rho-omega mixing matrix element Pi_{rho omega}(s), determined from e^+e^- -> pi^+ pi^- data. The omega->pi^+ pi^- partial width can be determined either from the time-like pion form factor or through the constraint that the mixed physical propagator D_{rho omega}^{mu nu}(s) possesses no poles. The two procedures are inequivalent in practice, and we show why the first is preferred, to find finally Br(omega->pi^+ pi^-) = 1.9 +/- 0.3%.
We investigate omega-phi meson mixing to leading order in chiral perturbation theory utilizing the antisymmetric tensor field formulation. We update the quark mass ratio R from rho-omega mixing, R = 42 \pm 4.
In the framework of the relativistic and gauge invariant spectral integral technique, we calculate radiative decays rho(770)-> gamma pi(140) and omega(780)-> gamma pi(140) supposing all mesons (pi, rho and omega) to be quark-antiquark states. The q anti-q wave functions found for mesons and photon lead to a reasonably good description of data ($Γ^{(exp)}_{ρ^{\pm} \toγπ^{\pm}}=68\pm 30$ keV, $Γ^{(exp)}_{ρ^{0}\toγπ^0}=77\pm 28$ keV, $Γ^{(exp)}_{ω\toγπ^0}=776\pm 45$ keV) that makes it possible to estimate the coupling for the bremsstrahlung emission of pion by quarks $g_π\equiv g_π(u\to d π)$. We…
One-loop corrections due to the intermediate $πN$ and $ρN$ states are studied in $ω$ photoproduction near threshold. Our results show that the coupled-channel effects should be taken into account in extracting reliable nucleon resonance parameters from the forthcoming vector meson photoproduction data in the resonance region.
We carry out a theoretical and Monte Carlo study on the $J/ψ$ decays into $ωππ$ and $K\bar{K}π$ through intermediate subthreshold $ρ$ meson by using SU(3)-symmetric Lagrangian approach. It is found that the subthreshold $ρ$ contribution is not negligible and may have significant influence on partial wave analysis of resonances in these channels, especially near the $ωπ$ and $K \bar{K}$ thresholds.
The ratio of branching fractions Br(X(3872) --> gamma J/psi)/ Br(X(3872) --> pi^+ pi^- J/psi) is studied by assuming that the X(3872) --> pi^+ pi^- J/psi decay proceeds through the rho^0 meson pole which is caused by the omega-rho^0 mixing. As the result, it is seen that the calculated ratio is compatible with the measured values of the ratio when X(3872) is an axial-vector tetra-quark state, while it would be much larger than the measurements when it is a charmonium. Therefore, the existing data on the ratio seem to favor the tetra-quark interpretation of X(3872) over the charmonium, although…
We investigate thermal photon emission rates in hot hadronic matter from a system consisting of pi, rho, and omega mesons. The rates are calculated using both relativistic kinetic theory with Born diagrams as well as thermal field theory at the two-loop level. This enables us to cross-check our calculations and to manage a pole contribution that arises in the Born approximation corresponding to the omega -> pi^0 gamma radiative decay. After implementing hadronic form factors to account for finite-size corrections, we find that the resulting photo-emission rates are comparable to existing resul…
Based on the Weinberg lagrangian or, in a new language, the lagrangian of hidden local symmetry added with the term induced by the anomalous lagrangian of Wess and Zumino, the dynamics of the decays rho to 4 pi and omega to 5 pi is considered. The excitation curves of rho resonance in its decay to 4 pi are obtained for the first time. The comparison with recent CMD-2 data is given. The partial widths of the decays omega to 2 pi^+ 2 pi^- pi^0 and omega to pi^+ pi^-3 pi^0 which can be measured on colliders with luminosity 10^{33}{cm }^{-2}{s}^{-1} are evaluated for the first time.
We show that even moderate excess of neutrons over protons in nuclear matter, such as in ${}^{208} Pb$, can lead to large $ρ$-$ω$ mixing at densities of the order of twice the nuclear saturation density and higher. The typical mixing angle is of the order of $10^o$. The mixing may result in noticeable shifts of the positions and widths of resonances. We also analyze temperature effects and find that temperatures up to 50 MeV have practically no effect on the mixing.
The decays rho(770) to 4 pi and omega(782) to 5pi are considered in detail in the approach based on the Weinberg Lagrangian obtained upon the nonlinear realization of chiral symmetry, added with the term induced by the anomalous Lagrangian of Wess and Zumino. The partial widths and excitation curves of the decays rho^0 to 2 pi^+ 2 pi^-, pi^+ pi^- 2 pi^0, rho^{+-} to 2 pi^{+-} pi^{-+} pi^0, rho^(+-} to pi^(+-} 3 pi^0 are evaluated for e^+e^- annihilation, photoproduction and tau lepton decays. The results of calculations are compared with the recent CMD-2 data on the decay rho^0 to 2 pi^+ 2 pi^…
In this paper we study two kinds of tau decays: (a) tau- --> (rho pi-,omega pi-, phi pi-, K*0 K-) nu(tau), which belong to Delta S=0 processes and (b) Delta S = 1 processes, like tau- --> (rho K-, omega K-, phi K-, \bar{K*0} pi-) nu(tau), in the framework of resonance chiral theory. We fit the tau- --> omega pi- nu(tau) spectral function and the invariant mass distribution of omega K in the process of tau- --> omega K- nu(tau) to get the values of unknown resonance couplings. Then we make a prediction for branching ratios of all channels.
We determine the magnitude, phase, and $s$-dependence of $ρ$-$ω$ ``mixing'' in the pion form factor in the time-like region through fits to $e^+e^- \ra π^+ π^-$ data. The associated systematic errors in these quantities, arising from the functional form used to fit the $ρ$ resonance, are small. The systematic errors in the $ρ$ mass and width, however, are larger than previously estimated.
It is shown that the relative sign between the $NNω$ and $πρω$ coupling constants can be determined most sensitively from $ω$ production processes in $NN$ collisions. Recent data on these reactions clearly favor the sign of the $πρω$ coupling constant which is opposite to that inferred from studies of the photoproduction reaction in combination with the vector meson dominance assumption and used by many authors. Implication of this finding in the description of other reactions is discussed.
