The Nambu–Jona–Lasinio model of light nuclei

The Nambu–Jona–Lasinio model of the deuteron suggested by Nambu and Jona–Lasinio (Phys. Rev. 124 (1961) 246) is formulated from the first principles of QCD. The deuteron appears as a neutron–proton collective excitation, i.e. a Cooper np–pair, induced by a phenomenological local four–nucleon interaction in the nuclear phase of QCD. The model describes the deuteron coupled to itself, nucleons and other particles through one–nucleon loop exchanges providing a minimal transfer of nucleon flavours from initial to final nuclear states and accounting for contributions of nucleon–loop anomalies which are completely determined by one–nucleon loop diagrams. The dominance of contributions of nucleon–loop anomalies to effective Lagrangians of low–energy nuclear interactions is justified in the large N _C expansion, where N _C is the number of quark colours. Received: 10 March 2000     

SU(3) coupling schemes for odd-odd nuclei in the interacting boson – fermion – fermion model with both odd proton and odd neutron in natural parity orbits

The SU^BFF(3) dynamical symmetry limits of interacting boson – fermion – fermion model are identified and they are appropriate for heavy deformed odd – odd nuclei for configurations with both the odd proton and odd neutron occupying all the natural parity orbits in the corresponding valence shells. There are three symmetry limits and their correspondence with two quasi-particle (proton-neutron) Nilsson configurations is established; one of the limits mixes both Nilsson n_z's and Λ's and other two limits mix only Nilsson Λ's. The ¹⁹¹Ir (d,t) ¹⁹⁰Ir single nucleon transfer spectroscopic strengths are well described by one of the symmetry limits that mixes only Nilsson Λ's. Received: 22 June 1998     

Nucleon Properties Below the Critical Point Temperature

In this paper, we extended our work (Abu-Shady, Int. J. Theory Phys. 49:2425, 2010) to include nucleon properties. The field equations have been solved in the mean-field approximation using the effective mesonic potential at finite temperature. We found that the nucleon first mass increases up to \frac45 T_c\frac{4}{5} T_{c} MeV (where T _c is the critical point temperature) then decreases at higher values of temperature which approach the critical temperature (T _c ). In addition, we found that the magnetic moments of the proton and neutron can be increased by increasing the temperature up to the critical temperature. Moreover, we examined the axial coupling constant g _A (0), and the pion-nucleon coupling constant g _πNN (0) as functions of temperature. The obtained results are compared with previous works. From the results, we conclude that finite temperature plays a significant role in the change of behavior of nucleon properties.     

Exchange effects during δ-isobar photoproduction on a polarized deuteron

Within the framework of the relativistic impulse approximation and the nucleon spectator model we have investigated the influence of exchange effects in the photoproduction of δ isobars on a polarized deuteron with subsequent decay into a proton and a π⁻-meson. We used two forms of propagator for the spinor-vector field of an δ isobar in the calculations. Nuclear Physics Research Institute, Tomsk Polytechnic University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 42, No. 2, pp. 3–8, February, 1999.     

Nucleon properties in the covariant quark-diquark model

In the covariant quark-diquark model the effective Bethe-Salpeter (BS) equations for the nucleon and the Δ are solved including scalar and axial vector diquark correlations. Their quark substructure is effectively taken into account in both, the interaction kernel of the BS equations and the currents employed to calculate nucleon observables. Electromagnetic current conservation is maintained. The electric form factors of proton and neutron match the data. Their magnetic moments improve considerably by including axial vector diquarks and photon induced scalar-axial vector transitions. The isoscalar magnetic moment can be reproduced, the isovector contribution is about 15% too small. The ratio μG _E/G _M and the axial and strong couplings g _A, g _NN, provide an upper bound on the relative importance of axial vector diquarks confirming that scalar diquarks nevertheless describe the dominant 2-quark correlations inside nucleons. Received: 3 July 2000 / Accepted: 15 August 2000     

Transversity GPD in photoproduction and electroproduction of two vector mesons

The chiral-odd generalized parton distribution (GPD), or transversity GPD, of the nucleon can be accessed experimentally through the photoproduction or electroproduction of two vector mesons on a polarized nucleon target, γ^(*)N→ρ₁ρ₂N’, where ρ₁ is produced at large transverse momentum, ρ₂ is transversely polarized, and the mesons are separated by a large rapidity gap. We predict the cross section for this process for both transverse and longitudinal ρ₂ production. To this end, we propose a model for the transversity GPD H_T(x,ξ,t) and give an estimate of the relative sizes of the transverse and longitudinal ρ₂ cross sections. We show that a dedicated experiment at high energy should be able to measure the transversity content of the proton.     

Understanding the proton spin “puzzle” with a new “minimal” quark model

We investigate the spin structure of the nucleon in an extended Jaffe-Lipkin quark model. In addition to the conventional 3q structure, different (3q)(Q ) admixtures in the nucleon wave function are also taken into account. The contributions to the nucleon spin from various components of the nucleon wave function are discussed. The effect due to the Melosh-Wigner rotation is also studied. It is shown that the Jaffe-Lipkin term is only important when antiquarks are negatively polarized. We arrive at a new “minimal” quark model, which is close to the naive quark model, in order to understand the proton spin “puzzle”. Received: 4 November 2000 / Accepted: 23 October 2001     

Longitudinal polarisation of Λ and Λ̄ hyperons in lepton–nucleon deep-inelastic scattering

We consider models for the spin transfers to Λ and Λ̄ hyperons produced in lepton–nucleon deep-inelastic scattering. We make predictions for longitudinal Λ and Λ̄ spin transfers for the COMPASS experiment and for HERA, and for the spin transfer to Λ hyperons produced at JLAB. We demonstrate that accurate measurements of the spin transfers to Λ and Λ̄ hyperons with COMPASS kinematics have the potential to probe the intrinsic strangeness in the nucleon. We show that a measurement of Λ̄ polarisation could provide a clean probe of the spin transfer from s̄ quarks and provides a new possibility to measure the antistrange quark distribution function. COMPASS data in a domain of x that has not been studied previously will provide valuable extra information to fix models for the nucleon spin structure. The spin transfer to Λ̄ hyperons, which could be measured by the COMPASS experiment, would provide a new tool to distinguish between the SU(6) and Burkardt–Jaffe (BJ) models for baryon spin structure. In the case of the HERA electron–proton collider experiments with longitudinally-polarised electrons, the separation between the target and current fragmentation mechanisms is more clear. It provides a complementary probe of the strange quark distribution and helps distinguish between the SU(6) and BJ models for the Λ and Λ̄ spin structure. Finally, we show that the spin transfer to Λ hyperons measured in a JLAB experiment would be dominated by the spin transfer of the intrinsic polarised-strangeness in the remnant nucleon, providing an independent way to check our model predictions. PACS 13.60.Rj; 13.87.Fh; 13.88.+e; 14.40.Ev; 14.20.Jn     

Solvatochromic shift of the 0-0 phosphorescence band and change of polarizability in the a 1δg → X 3Σ g? -transition in the oxygen molecule

We used known experimental data to analyze the influence of intermolecular interactions on the position of the 0-0-band a¹Δ_g → X³Σ _g ⁻ phosphorescence of molecular oxygen in solutions. A bathochromic (red) shift caused by dispersion interactions and fluctuations of the internal electric field (induction effect) is analyzed employing new formulas obtained by us in the framework of the Onsager model. The contributions from intermolecular repulsion and higher multipole interactions to the shift of the spectrum are also discussed. It is found that the polarizability in the a¹Δ_g state is higher than in the X³Σ _g ^t- state by 0.19 ± 0.03 ų. Taking into account the induced nature of O₂ phosphorescence in solutions, it is noted that the change of polarizability Δα_eg = 0.19 ų should differ from the change of Δα_eg inherent in free molecular oxygen. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 453–459, July–August, 2007.     

On narrow nucleon excitation <Emphasis Type="Italic">N</Emphasis>*(1685)

We perform estimates on putative narrow nucleon N* (1685), which is a candidate for the non-strange member of the exotic anti-decuplet of baryons. In particular, we consider the recent high precision data on η photoproduction off free proton obtained by the Crystal Ball Collaboration at MAMI. We show that it is difficult to describe peculiarities of these new data in the invariant energy interval of W ∼ 1650–1750 MeV in terms of known wide resonances. Using very simple estimates, we show that the data may indicate an existence of a narrow N* (1685) with small photocoupling to the proton.     

Study of the charge dependence of the pion–nucleon coupling constant on the basis of data on low-energy nucleon–nucleon interactions

The relation between quantities that characterize the pion–nucleon and nucleon–nucleon interactions is studied with allowance for the fact that, at low energies, nuclear forces in nucleon–nucleon systems are mediated predominantly by one-pion exchange. On the basis of the values currently recommended for the low-energy parameters of the proton–proton interaction, the charged pion–nucleon coupling constant is evaluated at g_π²±/4π = 14.55(13). This value is in perfect agreement with the experimental value of g_π²±/4π = 14.52(26) found by the Uppsala Neutron Research Group. At the same time, the value obtained for the charged pion–nucleon coupling constant differs sizably from the value of the pion–nucleon coupling constant for neutral pions, which is g_π² 0/4π = 13.55(13). This is indicative of a substantial charge dependence of the coupling constant.     

Three-dimensional parton distribution functions g1T and $h_{1L}^{\perp}$ in the polarized proton–antiproton Drell–Yan process

We present predictions of the unweighted and weighted double spin asymmetries related to the transversal helicity distribution g _1T and the longitudinal transversity distribution h_1L^{^}h_{1L}^{\perp}, two of eight leading-twist transverse momentum dependent parton distributions (TMDs) or three-dimensional parton distribution functions (3dPDFs), in the polarized proton–antiproton Drell–Yan process at typical kinematics on the Facility for Antiproton and Ion Research (FAIR). We conclude that FAIR is ideal to access the new 3dPDFs toward a detailed picture of the nucleon structure.     

Bounds on non-leading QCD effects in a quark model for inclusive reactions

We study the possible effect of QCD in the proton wave function in a quark model for inclusive processesA+B→C+X pursued by us. The assumption is the validity of the conjecture of Lepage and Brodsky in QCD on such effects. Our results obey the perturbative expectation, |R _g tan² φ|<1. Symmetric version of the model is, however, found to be at variance with most of the inclusive data as well as with some known phenomenology. If the dynamics of the underlying theory generate Regge-like symmetry breaking approximately, the model is phenomenologically viable, and the non-leading QCD effects become reasonable in size. Phenomenological necessity of the admixtures of (56, 0⁺)*, (70, 0⁺) and (56, 2⁺) in the nucleon wave function is also discussed in the present analysis.     

A systematic study of J/ψ suppression in cold nuclear matter

Understanding the effects of cold nuclear matter on J/ψ production is a key requirement for interpreting the J/ψ suppression reported in heavy-ion collisions. Based on a Glauber model, the J/ψ–nucleon inelastic cross section is determined from a statistical analysis of the J/ψ world data on nuclear targets. The global fit of all data gives σ_J/ψN = 3.4 ± 0.2 mb, significantly smaller than previous estimates, yet the χ² of the fit is pretty large, χ²/ndf=1.5. A similar value, σ_J/ψN = 3.5 ± 0.2 ± 1.7 mb, is obtained when the De Florian–Sassot modifications of the nuclear parton densities are included in the analysis, although we emphasise that the present uncertainties on gluon (anti-) shadowing do not allow for a precise determination of σ_J/ψN. Finally, the possible energy dependence of the J/ψ–nucleon inelastic cross section is investigated within this framework. No significant energy dependence of the J/ψ–N interaction is observed. PACS  25.75.-q; 14.40.Gx; 24.85.+p     

Spray generator of singlet oxygen for a chemical oxygen-iodine laser

A spray type of singlet oxygen generator for driving the Chemical Oxygen-Iodine Laser was developed. Singlet oxygen, O₂(¹Δ_g), is generated by a fast reaction of chlorine with basic hydrogen peroxide solution in the form of a dense spray. A mathematical model of this reaction system showed that O₂(¹Δ_g) can be generated in this system with a high yield (0.70–0.80), high utilization of chlorine (0.75–0.95), and effective utilization of liquid (0.36–0.54) at very high generator pressures (35–75 kPa). Experimental studies of this reaction system without an efficient separation of liquid proved an efficient O₂(¹Δ_g) production characterized by a rather high product of chlorine utilization and O₂(¹Δ_g) yield (0.4–0.9) at very high generator pressures (30–80 kPa). This pressure is much higher than the operation pressure used in other generators, which should be beneficial for a pressure recovery system of the COIL. These results provided the basis for designing a centrifugal spray generator with an efficient separation of liquid from the gas flow, which is the subject of the following paper.     

Implications of the JLab proton polarization data for the behavior of strange nucleon form factors

A special eight-resonance unitary and analytic model of nucleon electromagnetic structure is used to analyze first the classical proton form factor data obtained by the Rosenbluth technique, and then also the contradictory JLab proton polarization data on the ratio μ_p G _Ep(Q ²)/G _Mp(Q ²) , with the aim to investigate the implications of the latter for the behavior of strange nucleon form factors.     

Chiral invariant phase space event generator

The Geant4 CHIPS model simulates both decay and nuclear capture of negative muons. In hadron level models the muon is captured by a proton, p(μ,ν_μ)n , and the neutron transfers to the nucleus only 5MeV, which is not enough to split a nucleon from the nucleus, while the measured spectra of emitted nucleons reach 80MeV. In CHIPS, which considers asymptotically free quark-partons, the muon can be captured by a quark, u(μ,ν_μ)d , and transfers 52MeV to the nucleus. This capture mechanism fits the main part of the nucleon spectra, while the high-energy part of the spectra is not fitted. A precise fit of the high-energy part of the nucleon spectra can be made if the muon decay μ → dˉν_μ is taken into account.     

Dual analytic model of generalized parton distributions

A model for generalized parton distributions (GPDs) in the form of ∼(x/g ₀)^{(1−x)ᾶ(t)}, where ᾶ(t) = α(t) − α(0) is the nonlinear part of the Regge trajectory and g ₀ is a parameter, g ₀ > 1, is presented. For linear trajectories, it reduces to earlier proposals. We compare the calculated moments of these GPDs with the experimental data on form factors and find that the effects from the nonlinearity of Regge trajectories are large. By Fourier transforming the obtained GPDs, we access the spatial distribution of protons in the transverse plane. The relation between dual amplitudes with Mandelstam analyticity and composite models in the infinite-momentum frame is discussed, the integration variable in dual models being associated with the quark longitudinal-momentum fraction x in the nucleon. The text was submitted by the authors in English.     

Novel approach to pion and eta production in proton-proton collisions near threshold

We evaluate the threshold matrix–element for the reaction pp→ppπ⁰ in a fully relativistic Feynman diagrammatic approach. We employ a simple effective range approximation to take care of the S–wave pp final–state interaction. The experimental value for the threshold amplitude A = (2.7 −i0.3) fm⁴ can be reproduced by contributions from tree level chiral (long–range) pion exchange and short–range effects related to vector meson exchanges, with ω-exchange giving the largest individual contribution. Pion loop effects appear to be small. We stress that the commonly used heavy baryon formalism is not applicable in the NN–system above the pion production threshold due to the large external momentum, |p|≃ (Mm _π)^−1/2, with M and m _π the nucleon and the pion mass, respectively. We furthermore investigate the reaction pp→pnπ⁺ near threshold within the same approach. We extract from the data the triplet threshold amplitude as B = (2.8 −i1.5) fm⁴. Its real part can be well understood from (relativistic) tree level meson–exchange diagrams. In addition, we investigate the process pp→ppη near threshold. We use a simple factorization ansatz for the ppη final–state interaction and extract from the data the modulus of the threshold amplitude, |C|= 1.32 fm⁴. With g _ηN= 5.3, this value can be reproduced by (relativistic) tree level meson–exchange diagrams and η–rescattering, whose strength is fixed by the ηN scattering length. We also comment on the recent near threshold data for η^′–production. Received: 27 November 1998