Nonresonant muon pair production in electron-positron annihilation in the field of light wave

In the frame of the Born approximation it was theoretically investigated nonresonant muon pair production in e ⁺ e ⁻ collision in the field of elliptically polarized electromagnetic wave in the general relativistic case. It was analyzed in detail the reaction kinematics. It was derived the expressions for the amplitude and the cross section of the nonresonant muon pair production in e ⁺ e ⁻ annihilation in the moderately strong field. It was demonstrated that the partial cross-section is factorized as a product of the cross section of the muon pair production from e ⁺ e ⁻ pair in the absence of the external field and the probability of emission and absorption of photons from the wave. Original Text ? Astro, Ltd., 2009. The article is published in the original.     

Quark momentum-space charge distribution in deuteron and neutron/proton structure functions ratio

The electromagnetic polarizabilities of the nucleon are shown to be essentially composed of the nonresonant α _p(E ₀₊) = + 3.2, α _n(E ₀₊) = + 4.1, the t-channel α ^t _{p, n} = - β ^t _{p, n} = + 7.6 and the resonant β _{p, n}(P ₃₃(1232)) = + 8.3 contributions (in units of 10^-4fm^3). The remaining deviations from the experimental data Δα _p = 1.2±0.6, Δβ _p = 1.2±0.6, Δα _n = 0.8±1.7 and Δβ _n = 2.0±1.8 are contributed by a larger number of resonant and nonresonant processes with cancellations between the contributions. This result confirms that dominant contributions to the electric and magnetic polarizabilities may be represented in terms of two-photon coupling to the σ-meson having the predicted mass m _σ = 666MeV and two-photon width Γ _γγ = 2.6keV.     

Reaction48Ca (p,n)48Sc fromE p =1.885 to 5.1 MeV

The total (p, n) reaction cross section for⁴⁸Ca has been measured as a function of proton energy in the energy range 1.885 to 5.100 MeV with an overall resolution of ∼ 2 keV and in ∼ 5 keV energy steps. The fluctutions in fine resolution data have been analysed to determine the average coherence width 〈Γ〉. The excitation function averaged over large energy intervals has been analyzed in terms of the optical model. The isobaric analogue resonances atE _p ∼ 1.95 and 4 MeV have been shape-analyzed to extract the proton partial width and the spectroscopic factorS _n . A comparison of the gross structures observed in ∼ 55 keV averaged excitation function with the predictions of Izumo’s partial equilibrium model has also been made.     

Nonresonance spin-lattice absorption of ultrasound in Ising magnets

A theory of nonresonant acoustic absorption in Ising magnets is constructed by the nonequilibrium statistical operator method. It is assumed that the spins are coupled with the sound via modulation of the Ising exchange integral, and the nonresonant absorption is due to the interaction of the spin system with the thermal vibrations of the lattice. The frequency dependence of the absorption χ″(ω), which has an analytical form different from that of the well-known Debye function, is determined. The temperature dependence of χ″(ω), which is made up of 1) the averages of the vibrational variables and 2) the temperature dependence of the spin correlation functions of the linear Ising model, is analyzed. It is shown that the cross-coupling of the two subsystems (Ising and Zeeman) produces a second absorption peak at low frequencies together with the peak characteristic of the Debye curve. Fiz. Tverd. Tela (St. Petersburg) 39, 516–521 (March 1997)     

Further evidence for formation of a narrow baryon resonance with positive strangeness in K + collisions with Xe nuclei

We have continued our investigation of the charge-exchange reaction K ⁺Xe → K ⁰ pXe’ in the bubble chamber DIANA. In agreement with our previous results based on part of the present statistics, formation of a narrow pK ⁰ resonance with mass of 1537 ± 2 MeV/c ² is observed in the elementary transition K ⁺ n → K ⁰ p on a neutron bound in the xenon nucleus. The visible width of the peak is consistent with being entirely due to instrumental resolution and allows one to place an upper limit on its intrinsic width: Γ < 9 MeV/c ². A more precise estimate of the resonance intrinsic width, Γ = 0.36 ± 0.11 MeV/c ², is obtained from the ratio between the numbers of resonant and nonresonant charge-exchange events. The signal is observed in a restricted interval of incident K ⁺ momentum that is consistent with smearing of a narrow pK ⁰ resonance by Fermi motion of the target neutron. The statistical significance of the signal is some 7.3, 5.3, and 4.3 standard deviations for the estimators and , respectively. This observation confirms and reinforces our earlier results, and offers strong evidence for formation of a pentaquark baryon with positive strangeness in the charge-exchange reaction K ⁺ n → K ⁰ p on a bound neutron. (The DIANA Collaboration) The text was submitted by the authors in English.     

Mechanism of the production of the <Emphasis Type="Italic">a</Emphasis><Subscript>0</Subscript>(980) resonance in the γγ → π<Superscript>0</Superscript>η reaction

High-statistics Belle data on the γγ → π⁰η reaction have been analyzed in order to reveal the mechanism of two-photon production and the nature of the a ₀(980) resonance. The solution obtained for the γγ → π⁰η amplitude is in agreement with the predictions of the chiral theory for the πη-scattering length; with the strong coupling of the a ₀(980) resonance with the πη, K $ \bar K $ \bar K , and πη′ channels; and with the key role of the a ₀(980) → (K $ \bar K $ \bar K + π⁰η + π⁰η′) → γγ rescattering mechanisms in the a ₀(980) → γγ decay. This picture is much in favor of the q ² $ \bar q $ \bar q ² nature of a ₀(980) resonance and is consistent with the properties of its partners, σ₀(600) and f ₀(980) resonances, in particular, with those manifested in the γγ → ππ reactions. The important role of vector exchanges in the formation of the nonresonant background in the γγ → π⁰η reaction has been revealed. Preliminary information on the π⁰η → π⁰η reaction has been obtained.     

Overcoming of the gamow tunneling insufficiencies by maximizing the damp-matching resonant tunneling

The resonant quantum tunneling current through the barrier between two wells may be maximized when the damp (absorption) in one well matches the barrier parameters. The maximum resonant tunneling current is much greater than the conventional expectation by a factor ofθ (1/θ ² is the Gamow tunneling factor). It is shown that with all the established quantum mechanics, very much higher reaction probabilities between nuclei in contrary to the Gamow theory can be explained in agreement with experiments. Particularly, the resonance will select the sub-barrier fusion with a suitable fusion rate which matches the barrier parameters. This selective resonant tunneling model is able to explain both the hot fusion data (e.g. the width of resonance in¹¹B(p,α)2α reaction) and the cold fusion data (e.g. “excess heat” without any commensurate neutron andγ radiation). This work is supported by the State Commission of Science and Technology, the Natural Science Foundation of China (Contract #19645005), and the Fundamental Research Fund of Tsinghua University.     

Uncertainties in the 0νββ-decay nuclear matrix elements

The nuclear matrix elements M ^0ν of the neutrinoless double-beta decay (0νβ β) of most nuclei with known 2νββ-decay rates are systematically evaluated using the Quasiparticle Random Phase Approximation (QRPA) and Renormalized QRPA (RQRPA). The experimental 2νβ β-decay rate is used to adjust the most relevant parameter, the strength of the particle-particle interaction. With such procedure the M ^0ν values become essentially independent of single-particle basis size, the axial vector quenching factor, etc. Theoretical arguments in favor of the adopted way of determining the interaction parameters are presented. It is suggested that most of the spread among the published M ^0ν ’s can be ascribed to the choices of implicit and explicit parameters, inherent to the QRPA method. Presented by V. Rodin at the Workshop on calculation of double-beta-decay matrix elements (MEDEX’05), Corfu, Greece, September 26–29, 2005.     

Recent Result of Muon Catalyzed t–t Fusion at RIKEN-RAL

We have measured X-rays and neutrons associated with the muon catalyzed t–t fusion process at the RIKEN-RAL Muon facility. In the X-ray measurement, we observed K_α and K_β X-rays originating from the muon sticking process in muon catalyzed t–t fusion, and obtained the K_α X-ray yield and the K_β/K_α intensity ratio. An average recoil energy of the (μ⁻α) atoms in a solid T₂ medium was determined from the observed Doppler broadening width of the K_α X-ray line. The obtained t–t fusion neutron has shown an exponential time spectrum with a single component and a continuous energy spectrum with a maximum energy of 9 MeV. We have determined the t–t fusion neutron yield, the t–t fusion cycling rate and the muon sticking probability from the neutron data. The obtained maximum neutron energy is a very peculiar value from the view point of the reaction Q value (11.33 MeV) with the three-particle decay mode at the exit channel: t + t → α + n + n + Q. The obtained neutron energy distribution was analyzed by a simple model with two neutron energy components; reasonable agreement has been obtained, suggesting a strong (n–α) correlation in the exit channel of the t–t muon catalyzed fusion reaction. This revised version was published online in August 2006 with corrections to the Cover Date.     

Birkhoff Normal Form for Some Nonlinear PDEs

 We consider the problem of extending to PDEs Birkhoff normal form theorem on Hamiltonian systems close to nonresonant elliptic equilibria. As a model problem we take the nonlinear wave equation

Extension of the Random-Phase Approximation for <Emphasis Type="Italic">γ</Emphasis>-soft nuclei

The variational method is formulated which extends the Random-Phase Approximation to γ-soft nuclei.     

The peculiarities of crystallization of low-temperature eutectic in magnesium-lead system

Density of low-temperature eutectic in magnesium-lead system (83.06 at. % Pb) has been measured by gamma-raying of the samples with narrow beam from cesium-137 isotope over the temperature range 293–1000 K of solid and liquid states. Approximation density dependences have been obtained and data of this work and other authors have been compared. Reference tables of temperature dependences of the alloy thermal properties have been compiled for the entire range of measurements and their errors estimated. It is shown that differences in the values of volumetric changes obtained during melting and crystallization are bound with the metastable β′-phase formation.     

ω(→ π+π?π0) meson photoproduction on proton

The cross-section for the π ⁺ π ⁻ π ⁰ invariant mass distribution in the γp reaction in the GeV region is calculated. This reaction is assumed to proceed through the formation of the ω-meson in the intermediate state, because the production cross-section for this meson in the γp reaction in the GeV region is significant and it has a large branching ratio (88.8%) in the π ⁺ π ⁻ π ⁰ channel. The cross-sections for this reaction are calculated using the energy-dependent reaction amplitude, f _γp→ωp(0), extracted from the latest ω-meson photoproduction data. We use established procedure to calculate other factors, like width and propagator of the ω-meson, so that our calculation can provide reliable cross-section. The calculated results reproduce the measured π ⁺ π ⁻ π ⁰ invariant mass distribution spectra in the γp reaction.     

α-particle spectrum in the reaction p + 11B → α + 8Be* → 3α

Using a simple phenomenological parametrization of the reaction amplitude we calculated α-particle spectrumin the reaction p + ¹¹B → α + ⁸Be* → 3α at the resonance proton energy of 675 keV. The parametrization includes Breit-Wigner factor with an energy-dependent width for intermediate ⁸Be* state and the Coulomb and the centrifugal factors in α-particle-emission vertices. The shape of the spectrum consists of a well-defined peak corresponding to emission of the primary α and a flat shoulder going down to very low energy. We found that below 1.5MeV there are 17.5% of α’s and below 1MeV there are 11% of them. The text was submitted by the author in English.     

a 0 + (980)-resonance production in the reaction pp → dπ + η close to the K\bar K threshold

The reaction pp → dπ ⁺ η has been measured at a beam energy of T _p = 2.65 GeV (p _p = 3.46 GeV/c) using the ANKE spectrometer at COSY-Julich. The missing-mass distribution of the detected dπ ⁺ pairs exhibits a peak around the η mass on top of a strong background of multipion pp → dπ ⁺(nπ) events. The differential cross section d ⁴ σ/dΩ_d dΩ _π ⁺ dp _d dp _π ⁺ for the reaction pp → dπ ⁺ η has been determined model independently for two regions of phase space. Employing a dynamical model for the a ₀ ⁺ production allows one then to deduce a total cross section of σ(pp → da ₀ ⁺ → dπ ⁺ η) = 1.1 ± 0.3_stat ± 0.7_syst μb for the production of π ⁺ η via the scalar a ₀ ⁺ (980) resonance and σ(pp → dπ ⁺ η) = 3.5 ± 0.3_stat ± 1.0_syst μb for the nonresonant production. Using the same model as for the interpretation of recent results from ANKE for the reaction , the ratio of the total cross sections is , which is in agreement with branching ratios in the literature. The text was submitted by the authors in English.     

The estimation of the Z′ gauge boson mass in E 6 models

The aim of this study is to estimate the Z′ boson mass by using the calculations of the decay width of Z′(ϑ) boson. So, the decay width of the extra Z boson is calculated numerically in effective rank 5 models for different mixing angles ϑ of the model and for different mass values of the extra Z boson. The decay width of Z′ boson to the Standard Model (SM) fermions is found to be between 4.42 and 19.36 GeV and the full decay width of Z′ boson to all particles is found to be between 20.88 and 37.15 GeV. We calculated the full decay width at the angle ϑ ≊ 0 for Z′ and Z ₂ → Z′. The full decay width of Z′ boson is written in a single equation according to our calculations. By using these calculations and the previous works the mass of Z′ boson and the number of generations of the exotic particles are estimated. The article is published in the original.     

Partial wave analysis of πproduction in two-photon collisions at LEP

The reaction γγ → π⁺π^-π⁰ with quasi-real photons is studied with a total integrated luminosity of 663pb^-1, collected by the L3 detector at LEP at center-of-mass energies from 183 to 209GeV. The results of an energy-dependent partial wave analysis in the mass region 1.1≤M(π⁺π^-π⁰)≤2.2GeV are presented. The reaction is dominated by a₂(1320) formation. A strong signal consistent with the first radial excitation of the isovector tensor state, a₂(1700), is present and confirms the previous L3 observation. Its two-photon partial width is found to be Br(3π) = 0.37^+0.12_-0.08keV, the relative branching ratio of ρ(770)π to f₂(1270)π is 3.4±0.4. For all observed states the product of γγ partial width and 3π branching ratios is measured.     

Addition and spin exchange rate constants by longitudinal field μSR: The Mu+NO reaction

The addition reaction Mu+NO+M→MuNO+M and the spin exchange reaction Mu(↑) +MO(↓)→Mu(↓)+NO(↑) have been measured by longitudinal field μSR at room temperature in the presence of up to 58 atm of N₂ as inert collider. The pressure dependence of the longitudinal relaxation rate due to the addition reaction (λ_c) demostrates that the system is still in the low pressure regime in this pressure range. The corresponding termolecular rate constant has been determined ask _0,Mu =(1.10±0.25)×10⁻³² cm⁶ molecules⁻² s⁻¹, almost 4 times smaller than the corresponding H atom reactionk _0,H=3.90×10⁻³² cm⁶ molecules⁻² s⁻¹ [I.M. Campbell et al., J. Chem. Soc. Faraday Trans. 1.71 (1975) 2097]. The average value of the spin exchange rate constants in the 2.5–58 atm pressure range,k _SE=(3.16±0.06)×10⁻¹⁰ cm³ molecule⁻¹ s⁻¹, is in good agreement with previous values obtained by transverse field μSR [D.G. Fleming et al., J. Chem. Phys. 73 (1980) 2751].     

Eight resonances and a half for the reaction <Emphasis Type="Italic">γ</Emphasis> + <Emphasis Type="Italic">p</Emphasis>→<Emphasis Type="Italic">η</Emphasis> + <Emphasis Type="Italic">p</Emphasis>

On the basis of the dynamical model for meson photoproduction on nucleons, it is shown that only eight broad resonances (of width in excess of 120 MeV), of which two belong to the class of missing resonances, are required for reproducing experimental data from the threshold for the reaction γp → ηp to the photon energy of 3 GeV.     

Current non-conservation effects in ultra-high energy neutrino interactions

The overall hardness scale of the ultra-high energy neutrino-nucleon interactions is usually estimated as Q ² ∼ m _w ² The effect of non-conservation of weak currents pushes this scale up to the top quark mass squared and changes dynamics of the scattering process. The Double Leading Log Approximation provides simple and numerically accurate formula for the top-bottom contribution to the total cross section σ^νN . Corresponding correction to σ^νN appears to be numerically large. It is comparable with the leading contribution evaluated in the massless quark approximation.