Two schemes ofη−η′-mixing

Proceeding from the expansion of composite operators in interpolating hadronic fields, the width of the decays η(η′)→γγ andJ/ψ→η(η′)γ have been calculated. Two mechanisms of pseudoscalar field mixing (“mass-mixing” and “current-mixing”) are considered. In the given schemes, the values of η?η′-mixing angle θ _p are, respectively, (?15.0±1.8)^o and (?19.7±2.2)^o.     

Search for a new light gauge boson in π0, η and η′ decays

Upper limits for the production of new light gauge bosons in π⁰, η and η′ decays have been obtained with the Crystal Barrel detector. The kinematically well-constrained reactions p?p → π⁰π⁰ P have been studied, where P ? π ⁰, η, η′ decays through the emission of a single photon recoiling against a missing state X. X can be a long-lived weakly interacting particle or it decays into ???. The resulting branching ratio upper limits (90 % C.L.) are: 6 × 10^?5 for masses M _X of the missing particle X lying between 65 MeV/c² and 125 MeV/c² (π⁰ decay), 6 × 10^?5 for M _X between 200 MeV/c² and 525 MeV/c² (gh decay), and 4 × 10^?5 for M _X between 50 MeV/c² and 925 MeV/c² (η′ decay). The π⁰-decay limit represents an improvement by a factor of 4 to 8 (depending on M _X) when compared to the existing limit, whereas the η and η′ decay limits have been measured for the first time, thereby extending the M _X range from 125 MeV/c² up to 925 MeV/c².     

Penguins,trees and final state interactions in B decays in broken SU3

The availability of data on B_s decays to strange quasi-two-body final states, either with or without charmonium opens new possibilities for understanding different contributions of weak diagrams and in particular the relative contributions of tree and penguin diagrams. Corresponding B_d and B_s decays to charge conjugate final states are equal in the SU(3) symmetry limit and the dominant SU(3) breaking mechanism is given by ratios of CKM matrix elements. Final State Interactions effects should be small, because strong interactions conserve C and should tend to cancel in ratios between charge conjugate states. Particularly interesting implications of decays into final states containing η and η′ are discussed.     

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).     

Looking for new gauge bosons in radiative decays of pseudoscalar mesons

We perform the model independent analysis of possibilities of looking for new gauge bosons in radiative decays of π⁰, η, η′ mesons. For this purpose we consider various experimental constraints on properties of light gauge bosons. It is shown that the branching ratios of these decays can be as large as: BR(π⁰→γ+X)?10^?3, BR(η→γ+X)?10^?4, BR(η′→γ+X)?10^?6, what is highly interesting from the experimental point of view.     

Decays τ → (η, η')<Emphasis Type="Italic">K</Emphasis>–ν<Subscript>τ</Subscript> in the extended Nambu–Jona-Lasinio model

The decays τ → (η, η')K–ν_τ are described in the framework of the extended Nambu–Jona-Lasinio model. Both full and differential widths of these decays are calculated. The vector and scalar channels are considered. In the vector channel, the subprocesses with the intermediate K*(892) and K*(1410) mesons play the main role. In the scalar channel, the subprocesses with the intermediate and K₀^*(800) and K₀^*(1430) mesons are taken into account. The scalar channel gives an insignificant contribution to the full width of the decay τ → ηK–ν_τ. The obtained results are in satisfactory agreement with the experimental data. The prediction for the width of the process τ → η′K–ν_τ is made.     

ηc Physics at BESⅢ

An introduction for η_c physics research is presented in this paper, which shows that the meachnism of η_c decays can't be well described by current theoretical models and detailed experimental measurements need to be done with larger η_c sample. Based on the expected J/ψ and ψ′events taken with the planed BESⅢ detector in one year, the η_c physics researches are discussed extensively, including the measurements of branching fractions of different final states, the search for new decay modes, precision measurements of mass and width, and the search for rare decays. At last, the study of η′_c decays is also discussed briefly.     

Neutral decays ofη′(958)

The partial widths of the η′(958) decays into 2γ, ωγ, 3π⁰ andηπ⁰π⁰ have been measured with the GAMS-2000 spectrometer at the 70 GeV IHEP accelerator. Upper limits for the η′ decays into 3γ, π⁰γγ, 2π⁰ and 4π⁰ have also been obtained. The slope of a linear matrix element for theG-parity violating decayη′→3π⁰ has been determined.     

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.     

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.     

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.     

Hadronic decays of η and η′ in the large-N limit

Working in the large-N approximation (N being the number of colors), we relate thestrong η′→ηππ processes to theweak K _L→πππ decays. Chiral corrections are crucial to reproduce the experimental data. The isospin-violating η(η′)→πππ and the weakη→K ⁺π^- decays are also treated in this framework. We comment on the predictions of a “QCD-inspired” approach which determines in principle the chiral symmetry-breaking scales considered, and consequently the Skyrme coupling.     

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.     

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°.     

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.     

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.     

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.     

Further Analysis of Di-gluon Fusion Mechanismfor the Decays of B→Kη′

Di-gluon fusion mechanism might account for the large branching ratios of B→Kη′. But because we know little about the effective η′ɡɡ vertex, there are large uncertainties in perturbative QCD estimations. In this paper, we try several kinds of η′ɡɡ form factors and compare the numerical results with the experiment. We find that, though we know little about η′ɡɡ form factor, if di-gluon fusion mechanism is important in B→Kη′, the branching ratios of the decays B→K^*η′ would be around 10^－5 which can be tested by future experiments.