Instanton-induced flavour mixing in mesons

The U_L(N_f)×U_R(N_f) chiral symmetric version of the Nambu-Jona-Lasinio model is extended by the 't Hooft determinant and bosonized for an arbitrary number of flavours N_f. The resulting effective meson lagrangian is explicitly calculated to leading order in the derivatives for three flavours. The 't Hooft determinant induces flavour mixing of the mesons with diagonal flavour content (π⁰, η, η′, and their scalar chiral partners δ⁰, S, ϵ) and pushes up the physical η′-mass. The η-η′ mixing angle is found to be −31°.     

Pseudoscalar glueball in terms of composite interpolating fields

The pseudoscalar (PS) glueball is described with an account of the quark-gluon mixing and strict observation of the QCD local gauge and renormalization invariance. The lower limits on the mass and total width are established. The partial radiative decay widths and the PS-glueball production inJ/gY radiative decays are calculated. The consistency of the results with the η- and η′-meson data onJ/Ψ→PV decays is verified. On the basis of the results, the lower PS-glueball state may be identified with the upper iota state η(1490).     

The radial excitations of η−η′ mesons

The possibility of identification of a number of the recently discoveredJ ^PC=0^?+ isosinglet resonances (the ζ(1275), ι(1460) and others) as radial excitations of the η(549)- and η′(958)-mesons is investigated within the earlier developed phenomenological approach to analyse radial excitations of light mesons. The widths of the electromagnetic and strong decays of these mesons and the branching ratios of their production in the radiativeJ/ψ decay, as well as in the π^- p charge exchange reaction, are estimated. It is pointed out that the abundant production of the ι-meson in theJ/ψ-decays and the small width of the ι→2γ decay put forward repeatedly as an evidence for the glueball nature of this meson, can qualitatively be obtained in one of the considered schemes of the radial excitations of the η?η′-system.     

Non-perturbative treatment of hyperfine interaction in charmonium; a clue to understanding the pseudoscalars?

We give arguments that the wave function of η _c is relativistic and strongly localized while that of η _c , though non-relativistic, looks quite different from what is naively expected. This has consequences for the overlap integrals with ψ and ψ′ and may solve the problems associated with magnetic transitions. The hadronic width of η _c is expected around 20 MeV, that of η _c ^′ can become very small.     

Low energy effective Lagrangian description of η and η′ decays

A chiral Lagrangian incorporating a resolution of theU(1) problem is used to study some aspects of the η?η′ system. Mass relations, mixing angle predictions, and the 3π decay modes of η and η?η′ are obtained to be of the correct order of magnitude. Supplementing this Lagrangian with certain four derivative terms gives a rate for η?η′→ηππ which is nonvanishing in the chiral limit and in reasonable agreement with experiment. Some of the radiative decays of η and η′ are also discussed.     

Gibbs vs. Shannon entropies

The Gibbs neg-entropy -η_G=∫ II ln II is compared to the Shannon negentropy η_s=∑p Inp. The coarse-grained density is II, whilep is a probability sequence. Both objects are defined over partitions of the energy shell within a set-theoretic framework. The dissimilarity of these functionals is exhibited throughη _G vs._G η _S curves. A positive information interpretation of η_G is given referring it to the maximum information contained in the solution to the Liouville equation. The physical relevance ofη _G over η_S in classical physics is argued. In quantum mechanics, the fine-grained Shannon entropy remains relevant to the uncertainty principle, while the coarsegrained densities maintain their properties as in the classical case.     

Note on the Paper “Gibbs vs. Shannon Entropies” by Richard L. Liboff

In addition to the comparison of the Gibbs negentropy η_G = ∫ Π ln Π to the Shannon negentropy ηs = ∑ E_iΠ_i ln(E_iΠ_i), discussed in the cited paper, a comparison of the former to η_s′=η_s?∑E _i lnE _i the decrease in uncertainty, is of general interest from an information-theoretic standpoint. It is shown that η_G and η_s′ are similar in the situation in question. The additivity properties of η_G are briefly discussed.     

Mixing of pseudoscalar mesons and M1 radiative decays

We discuss the mixing of pseudoscalar mesons, in particular SU(3) breaking effects, based on ideas abstracted from QCD. The admixtures of η and η′ in η_c are calculated and utilized to estimate the M1 radiative decays ψ → ηγ, η′γ. A reasonably consistent picture emerges for these decays as well as others involving only the light quarks.     

Search for η-mesic nuclei in the reaction d + C at JINR

Results of a search for quasi-bound states of the η-meson and a target nucleus obtained during several years using the internal target at the Nuclotron d-beam are presented. Formation of η-mesic nuclei was studied in the reaction d + C in the energy interval 1.5 to 2.2 GeV/nucl. Decay products of S₁₁ resonances excited by η-mesons captured by nucleons in the nuclear target have been analyzed. Measurements were performed with a scintillation spectrometer SCAN. Analysis of obtained data is presented.     

Volume viscosity and structure of n-propanol by ultrasonics

The adiabatic volume viscosities η_v and η′_v have been evaluated in n-propanol along with X₂ (the molefraction of molecules arranged in pairs with antiparallel dipole moments), using experimental ultrasonic absorption data in the temperature range 10°C to 80°C. Both η_v and η′_v decrease nonlinearly with temperature and the ratio η′_v/η_v is found to be nearly unity at all temperatures.     

Meson-gluonium mixing and the glueball candidate⇌i(1,460)

The mixing of the glueball candidate?i(1,460) with η and η′ is studied in a chiral symmetry breaking framework. Using the solutions of anomalous Ward identities for flavourU(3)×U(3), we find that the octet-singlet mixing angle is quite large and that our results are consistent with a large glueball component in?i(1,460) with moderate gluonium mixing in η and η′.     

Rapid viscous flow of a nematic liquid crystal in the vicinity of the nematic-smectic <Emphasis Type="Italic">A</Emphasis> transition

The resistance to shear flow is investigated theoretically for polar liquid crystals, such as 4-n-octyl-4′-and 4-n-octyloxy-4′-cyanobiphenyls. It is established that the lowest resistance to shear flow at temperatures in the vicinity of the nematic-smectic A phase transition point T _NA is observed when the nematic director is oriented perpendicular to both the flow velocity vector and the flow velocity gradient. The three Miesowicz shear viscosity coefficients η_i (i=1–3) at temperatures close to the phase transition temperature (tens of millikelvins from T _NA ) and far from this transition are calculated in the framework of the Ericksen-Leslie theory. The decrease in the viscosity coefficients in the order η₂>η₁>η ₃ is explained by the fact that fluctuations of the local smectic order in the nematic phase lead to a singular behavior of the viscosity coefficient η₂, whereas the other two viscosity coefficients η₁ and η₃ are not affected by order parameter fluctuations.     

Eta and omega meson production in medium energy π+-p and K−p interactions

The production of η(550) and ω(780) mesons is studied in π^±p interactions at 16 GeV/c and K^?p interactions at 10 and 16 GeV/c. Cross sections for exclusive channels are presented, and for the π⁺p data differential cross sections are given for quasi-inclusive production where the η or ω is required to be accompanied by charged particles only. Close similarities are observed between η, ω and also ?⁰(770) production in terms of longitudinal and transverse variables. By a rough estimate, the η, ω and ?⁰ inclusive yields are found to be in the ratio 0.32 : 0.85 : 1, respectively, for 16 GeV/cπ⁺p collisions. For non-peripheral production we estimate this same ratio to be 0.34 : 0.9 : 1.     

Measurement of the relative probability of the decay φ → η′γ in the channel η′ → ηπ0π0, η → γγ

The process e ⁺ e ^? → η′γ, η′ → η π⁰π⁰, η → γγ is investigated by an SND detector in experiment on a VEPP-2M equipment with colliding electron-positron beams. The analysis of experimental data yields a value of B(? → η′γ)=(6.7 _?4.2 ^+5.0 ±1.5)×10^?5 for the decay probability. Taking into account a previous measurement of this quantity by an SND detector in the decay channel η′ → π⁺π^?η, one finally obtains B(?→η ′γ)=(6.7 _?2.4 ^+2.8 ±0.8)×10^?5.     

In search of the ηc

We argue that the X(2.88) detected in π^?p → γγ + n at 40 GeV/c cannot be the η_c. We discuss the possibility that a qq?cc? state is produced there, probably the same state discovered in radiative decay of the J/ψ. Only at much higher energies is the η_c expected to dominate over qq?cc? in the π^?p interaction. We also discuss coherent photoproduction and find that four quark state production would dominate over η_c.     

Radiative decays J/ψ → η(')γ in perturbative QCD

With the recent investigations of the g^*g^*-η^(') transition form factor and η-η^' mixing scheme, we present an updated study of the radiative decays J/ψ → η^(')γ in perturbative QCD. The decays are taken as a test ground for the g^*g^*-η^(') transition form factors and the η-η^' mixing scheme. The form factors are found to be working for glunic η^' production and the mixing angle is constrained to be φ=35.1°±0.8°.