OZI Rule Violation Research Articles

Eta-nucleon and eta-prime-nucleon coupling constants in QCD and the role of gluons

Coupling constants of η and η′ mesons with nucleons have been calculated using the method of QCD sum rules. Starting from vacuum-to-meson correlation function of interpolating fields of two nucleons, its matrix element with respect to nucleon spinors has been considered. Coupling constants at the physical points have been estimated from extrapolation of results obtained at two other points. Anomalous glue has been found to give substantial contribution to the coupling constants and also accounts for a significant OZI-rule violation.

Measurement of OZI rule violation and spin alignment inϕandωproduction at COMPASS

The COMPASS collaboration at CERN dedicated the 2008 and 2009 run time to hadron spectroscopy measurements with emphasis on the mesonic sector. At 190 GeV/c beam momentum, diffractive and double-Reggeon/Pomeron production mechanisms contribute. Studying vector meson production allows to explore this relatively unknown transition domain. We present results on the ratio of production yields for p p →(1020) p p ϕ and p p → p p ω(782) and its xF dependence where we find an OZI rule violation in the order of a factor of 3. In addition, the spin alignment of ω and ϕ as a function of xF is investigated.

N*(1535) contribution in pp → ppη″ and pn → dφ

In an effective Lagrangian model we find that the N*(1535) resonance contribution might be important to the interpretation of the present data of the pp → ppη″ and pn → dφ reactions. The strong coupling strength of N* (1535) to η″ and φ are indicated, and the possible implication to the intrinsic component of N* (1535) is explored. These results may provide hints to the real origin of the OZI rule violation. It is stressed that further measurements could be performed at the Cooling Storage Ring (CSR) at Lanzhou of China.

Φ PRODUCTION IN pp COLLISIONS

The data for near-threshold cross section for the reaction pp → ppɸ published by the DISTO and ANKE Collaboration are analyzed in order to evaluate the OZI ratio at low energies by taking into account corrections from the kinematics and the final-state interaction. Combining these new data with the few measurements available at higher energies the limit for the OZI rule violation is evaluated and the possible contribution from a five-quark baryonic resonance coupled to the ɸp system is estimated.

Decays of J/ψ and ψ′ into vector and pseudoscalar mesons and the pseudoscalar glueball– mixing

We introduce a parametrization scheme for J/ψ(ψ′) → VP where the effects of SU(3) flavor symmetry breaking and doubly OZI-rule violation (DOZI) can be parametrized by certain parameters with explicit physical interpretations. This scheme can be used to clarify the glueball– mixing within the pseudoscalar mesons. We also include the contributions from the electromagnetic (EM) decays of J/ψ and ψ′ via J/ψ(ψ′) → γ* → VP. Via study of the isospin violated channels, such as J/ψ(ψ′) → ρη, ρη′, ωπ0 and ϕπ0, reasonable constraints on the EM decay contributions are obtained. With up-to-date experimental data for J/ψ(ψ′) → VP, J/ψ(ψ′) → γP and P → γγ, etc, we arrive at a consistent description of the mentioned processes with a minimal set of parameters. As a consequence, we find that there exists an overall suppression of the ψ′ → 3g form factors, which sheds some light on the long-standing ‘ρπ puzzle’. By determining the glueball components inside the pseudoscalar η and η′ in three different glueball– mixing schemes, we deduce that the lowest pseudoscalar glueball, if it exists, has a rather small component, and it makes η(1405) a preferable candidate for a 0−+ glueball.

Formula omitted] decay into light meson pairs and its implication of the scalar meson structures

In light of the recent data from BES Collaboration for χc0→VV, PP and SS, and from CLEO-c for ηη, η′η′ and ηη′, we present a detailed analysis of the decays of heavy quarkonia into light meson pairs such as χc0,2→VV, PP and SS in a recently proposed parametrization scheme. An overall agreement with the data is achieved in χc0,2→VV and PP, while in χc0→SS we find that a possible existence of glueball-qq¯ mixings is correlated with the OZI-rule violations, which can be further examined at CLEO-c and BESIII in χc0→SS measurement.

Charmonium Hadronic Decays and the OZI Rule Violation Effects

We discuss the scalar meson mixing scenario and present an OZI rule violation mechanism for understanding the scalar productions in charmoium hadronic decays. We stress that the OZI violation could play a key role in disentangling the structure of the scalars: f0(1370), f0(1500) and f0(1710).

Aspects of φ-meson production in proton-proton collisions

We analyze near-threshold cross section data for the reaction pp->pp phi published by the DISTO collaboration and recent, still preliminary results presented by the ANKE Collaboration. We formulate a procedure to evaluate the OZI ratio at low energies by taking into account corrections from the kinematics and the final-state interaction. Combining the new data with the few measurements available at higher energies we give a limit for the OZI rule violation and estimate the possible contribution from a five-quark baryonic resonance coupled to the phi-p system.

Glueball- [formula omitted] mixing and Okuba–Zweig–Iizuka rule violation in the hadronic decays of heavy quarkonia

We investigate the correlations between the scalar meson configurations and Okuba–Zweig–Iizuka (OZI) rule violations in the hadronic decays of heavy quarkonia, e.g., J / ψ and ϒ, into isoscalar vector meson ( ϕ and ω) and scalar mesons ( f 0 ( 1710 ) , f 0 ( 1500 ) , and f 0 ( 1370 ) ). It shows that the dramatic change of the values of the branching ratio fraction of ϕ f 0 / ω f 0 from low (e.g., in J / ψ decays) to high energies (e.g., in ϒ decays) will not only test the glueball- Q Q ¯ mixings, but also provide important information about the mysterious OZI-rule violations within the scalars.

Coherent study ofχc0,2→VV,PPandSS

We investigate the decays of ${\ensuremath{\chi}}_{c0,2}$ into vector meson pairs ($VV$), pseudoscalar pairs ($PP$), and scalar pairs ($SS$) in a general factorization scheme. The purpose is to clarify the role played by the OZI-rule violations and SU(3) flavour breakings in the decay transitions, and their correlations with the final-state meson wavefunctions. For ${\ensuremath{\chi}}_{c0,2}\ensuremath{\rightarrow}VV$ and $PP$, we obtain an overall self-contained description of the experimental data. Applying this factorization to ${\ensuremath{\chi}}_{c0}\ensuremath{\rightarrow}{f}_{0}^{i}{f}_{0}^{j}$, where $i,j=1,2,3$ denotes ${f}_{0}(1710)$, ${f}_{0}(1500)$ and ${f}_{0}(1370)$, respectively, we find that specific patterns will arise from the model predictions for the decay branching ratio magnitudes, and useful information about the structure of those three scalars can be abstracted.

Okubo-Zweig-Iizuka rule violation in photoproduction

We investigate OZI rule violation in $\ensuremath{\omega}$ and $\ensuremath{\phi}$-meson photoproduction off nucleons. Data on the total cross sections indicate a large $\ensuremath{\phi}/\ensuremath{\omega}$ ratio of about 0.8 at the maximal available photon energy that is in good agreement with expectations from QCD. On the other hand, data at large four-momentum transfer exhibit a ratio of about 0.07, showing that the perturbative QCD regime is not approached at $|t|>2\text{ }\text{ }{\mathrm{GeV}}^{2}$ and photon energies ${E}_{\ensuremath{\gamma}}<4\text{ }\text{ }\mathrm{GeV}$. The anomanously large $\ensuremath{\phi}/\ensuremath{\omega}$ ratio at low energies, that is close to the reaction threshold, remains to be explained within nonperturbative QCD.

Spin effects and baryon resonance dynamics in φ-meson photoproduction at few GeV

The diffractive $\phi$-meson photoproduction amplitude is dominated by the Pomeron exchange process and contains the terms that govern the spin-spin and spin-orbital interactions. We show that these terms are responsible for the spin-flip transitions at forward photoproduction angles and appear in the angular distributions of $\phi\to K^+K^-$ -decay in reactions with unpolarized and polarized photon beams. At large momentum transfers, the main contribution to the $\phi$-meson photoproduction is found to be due to the excitation of nucleon resonances. Combined analysis of $\omega$ and $\phi$ photoproduction indicates strong OZI-rule violation in $\phi NN^*$ - couplings. We also show that the spin observables are sensitive to the dynamics of $\phi$-meson photoproduction at large angles and could help distinguish different theoretical models of nucleon resonances. Predictions for spin effects in $\phi$-meson photoproduction are presented for future experimental tests.

Non-diffractive processes and status of OZI-rule in ω and φ-meson photoproduction

At large momentum transfers, the main contribution to the φ-meson photoproduction comes from the resonant channel. Combined analysis of the ω and φ - meson photoproduction indicates for the strong OZI-rule violation in φNN ∗ - couplings. The spin observables are sensitive to this effect and, moreover, could help to distinguish between different theoretical models of the resonant channel.

The φNN coupling from chiral loops

Starting from effective Lagrangians which combine a gauge formulation of vector meson dominance with chiral Lagrangians, the coupling of the φ to the nucleon, which is zero at tree level due to the OZI rule, is calculated perturbatively considering loop contributions to the electric and magnetic form factors. We obtain reasonably smaller values for both form factors than those for ρNN and consistent with the expected order of magnitude of the OZI rule violation. The role of the φ– ω mixing is also investigated.

Chiral order and fluctuations in multi-flavour QCD

Multi-flavour (N_f>=3) Chiral Perturbation Theory (ChPT) may exhibit instabilities due to vacuum fluctuations of sea q-bar q pairs. Keeping the fluctuations small would require a very precise fine-tuning of the low-energy constants L_4 and L_6 to L_4[crit](M_rho) = - 0.51 * 10^(-3), and L_6[crit](M_rho) = - 0.26 * 10^(-3). A small deviation from these critical values -- like the one suggested by the phenomenology of OZI-rule violation in the scalar channel -- is amplified by huge numerical factors inducing large effects of vacuum fluctuations. This would lead in particular to a strong N_f-dependence of chiral symmetry breaking and a suppression of multi-flavour chiral order parameters. A simple resummation is shown to cure the instability of N_f>=3 ChPT, but it modifies the standard expressions of some O(p^2) and O(p^4) low-energy parameters in terms of observables. On the other hand, for r=m_s/m > 15, the two-flavour condensate is not suppressed, due to the contribution induced by massive vacuum s-bar s pairs. Thanks to the latter, the standard two-flavour ChPT is protected from multi-flavour instabilities and could provide a well-defined expansion scheme in powers of non-strange quark masses.

Proton-Antiproton annihilation at 900 MeV/c into $\pi^0\pi^0\pi^0, \pi^0\pi^0\eta$ and $\pi^0\eta\eta$

The three reactions $\overline{p}p \rightarrow \pi^0\pi^0\pi^0$ , $\pi^0\pi^0\eta$ and $\pi^0\eta\eta$ in proton-antiproton annihilation in flight at 900 MeV/c are used to search for isoscalar $0^{++}$ and $2^{++}$ mesons in the mass range 1000–2000 MeV, in particular the $f_0(1710)$ . The description of both $\pi^0\pi^0\pi^0$ and $\pi^0\eta\eta$ data sets requires an isoscalar tensor resonance decaying into $\pi^0\pi^0$ and $\eta\eta$ with a mass of $(1867\pm46)$ MeV and a width of $(385\pm58)$ MeV. The ratio of partial widths $\Gamma(\eta\eta)/\Gamma(\pi\pi)$ is $0.27 \pm 0.10$ . The analyses of both $\pi^0\pi^0\pi^0$ and $\pi^0\eta\eta$ show no signal for the $f_0(1710)$ . The $\pi^0\eta\eta$ data set shows a strong signal of the $f_2^{\prime}(1525)$ suggesting a large OZI rule violation for tensor meson production in $\overline{p}p$ annihilation. The $\pi^0\pi^0\pi^0$ data set also requires the $f_2(1565)$ . The signal for the $f_2(1810)$ reported by earlier experiments is confirmed neither in $\pi^0\pi^0\pi^0$ nor in $\pi^0\eta\eta$ . The analysis of $\pi^0\pi^0\eta$ leads to an isovector tensor state decaying into $\pi^0\eta$ with a mass of $(1698\pm44)$ MeV and a width of $(265\pm55)$ MeV.

(FIELD) SYMMETRIZATION SELECTION RULES

QCD and QED exhibit an infinite set of three-point Green's functions that contain only OZI rule violating contributions, and (for QCD) are subleading in the large N c expansion. We prove that the QCD amplitude for a neutral hybrid 1-+ exotic current to create ηπ0 only comes from OZI rule violation contributions under certain conditions, and is subleading in N c .

Near-threshold ω-and φ-meson production in pn → dM reactions and OZI-rule violation

The reactions pn → dω and pn → dφ are investigated near the corresponding thresholds. The S-wave amplitudes are calculated within the two-step model described by a triangle graph with π, ρ, and ω mesons in the intermediate state. The cross sections for the reactions pn → dω and pn → dφ are predicted to be significantly larger than the cross sections for the corresponding reactions pp → ppω and pp → ppφ at the same values of the c.m. excess energy Q. The phi-to-omega yield ratio is found to be (34±10)×10−3.

The latest results from OBELIX

The most recent achievements of the analysis of the data collected by the OBELIX experiment at LEAR are presented. The most interesting results concern the apparent OZI-rule violation in some annihilation channels and the consequent explanation in terms of a polarized ( s s ) strangeness content of the nucleon, a further convincing evidence for the presence of two pseudoscalar states in the E ι region and finally the observation of a tantalizing anomaly in the total antineutron-proton cross section at very low momenta.

On the current status of OZI violation in πN and pp reactions

The available data on $\omega$ and $\phi$ production from $\pi N$ and $pp$ collisions are reanalyzed with respect to an OZI rule violation on the basis of transition matrix elements. The data are found to be compatible with a constant ratio $R$ up to excess energies $\epsilon{\approx}300$ MeV, however, the ratio $R$ deviates substantially from the SU(3) prediction based on the present knowledge of the $\phi-\omega$ mixing angle.