The cos2φ asymmetry of Drell–Yan and J/ψ production in unpolarized pp̄ scattering

We investigate the cos2φ azimuthal asymmetry in Drell–Yan and J/ψ production from unpolarized pp̄ scattering at GSI-HESR energies. The contribution to this asymmetry arising from the leading-twist Boer–Mulders function (x,k _T ²), which describes a correlation between the transverse momentum and the transverse spin of quarks in an unpolarized hadron, is explicitly evaluated, and predictions for the GSI-HESR kinematic regime are presented. We show that the cos2φ asymmetry is quite sizable both on the J/ψ peak and in the Drell–Yan continuum region. Therefore these processes may offer experimentally viable access to the Boer–Mulders function in the early unpolarized stage of GSI experiments.     

On the geometric origin of the equation ϕ,11 — ϕ,22 = eϕ — e-2ϕ

It is shown that the equation ,11 — ,22 = e — e^-2 determines the intrinsic geometry of the two-dimensional affine sphere in the three-dimensional unimodular affine space like the sine-Gordon equation describes the metric on the surface of a constant negative curvature in the three-dimensional Euclidean space. The linear equations that determine the moving frame on the affine sphere are the Lax operators to the equation ,11 — ,22 = e — e^-2.     

Gell-Mann-Low function in the ϕ4 theory

An algorithm is proposed for the determination of the asymptotics of a sum of a perturbation series from the given values of its coefficients in the strong-coupling limit. When applied to the ?⁴ theory, the algorithm yields the β(g)∝g ^α behavior with α≈1 at large g for the Gell-Mann-Low function.     

Large deviation estimates in the stochastic quantization ofϕ 2 4

We study in the small noise limit the behaviour of field trajectories for the process constructed by the authors in connection with the stochastic quantization of ₂ ⁴ . Due to the presence of infinite renormalization the usual large deviation techniques do not apply immediately and a new strategy has to be developed. We prove some estimates analogous to the Freidlin-Ventzel inequalities. From these it follows that the field trajectories suitably smeared in space over a scaler ₀ behave, when the noise is small, as the projection on the same scale of a field obeying a regularized stochastic equation with a large cut-off. However the estimates are not uniform in the cut-off and an interesting feature of the problem is that the scale over which the field is smeared determines whether the noise is sufficiently small for the estimates to apply.Laboratoire associé au CNRS UA 280     

Spin asymmetries in diffractive J/ϕ leptoproduction

In this report we calculate the cross section and A _ll asymmetry for the diffractive J/? leptoproduction. We study dependencies of the asymmetry on the structure of the Pomeron-proton coupling.     

Measurement of the beam asymmetry in η photoproduction off the proton

The beam asymmetry, Σ , was measured at ELSA in the reaction p → ηp using linearly polarised tagged photon beams, produced by coherent bremsstrahlung off a diamond. The crystal was oriented to provide polarised photons in the energy range E _γ = 800 to 1400MeV with the maximum polarisation of P _γ = 49 % obtained at 1305MeV. Both dominant decay modes of the η into two photons and 3π⁰ were used to extract the beam asymmetry from the azimuthal modulation of the cross-section. The measurements cover the angular range Θ_cm ≃ 50 -150 degrees. Large asymmetries up to 80% are observed, in agreement with a previous measurement. The eta-MAID model and the Bonn-Gatchina partial wave analysis describe the measurements, but the required partial waves differ significantly.     

Polarized angular distributions in the decays of the 3D2 state of charmonium produced in unpolarized proton–antiproton annihilation

Using the helicity formalism, we calculate the combined angular distribution functions of the polarized gamma photons and electron in the triple cascade process $\bar{\mathrm{p}}\mathrm{p}\to{}^{3}\mathrm{D}_{\mathrm{2}}\to\chi_{\mathrm{\mathrm{{J}}}}+\gamma_{\mathrm{1}}\to(\psi +\gamma_{\mathrm{2}})+\gamma_{\mathrm{1}}\to(\mathrm{e}^{+}+\mathrm{e}^{-})+\gamma_{\mathrm{1}}+\gamma_{\mathrm{2}}\ (\mathrm{{J}}=0,1,2)$ , when $\bar{\mathrm{p}}$ and p are unpolarized. We also present the partially integrated angular distribution functions in different cases. Our results show that by measuring the two-particle angular distribution of γ ₁ and γ ₂ and that of γ ₂ and e^? with the polarization of either one of the two particles, one can determine the relative magnitudes as well as the relative phases of all the helicity amplitudes in the two radiative decay processes ³D₂→χ _J+γ ₁ and χ _J→ψ+γ ₂.     

On the Reproduction of the Solar Activity Variations in the Range 2–40 Months in the Interplanetary Medium

Journal of Experimental and Theoretical Physics - We compare the quasi-biennial variations and Rieger-type variations (on a timescale of less than 1 year) in solar activity, interplanetary...     

A new proof of the existence and nontriviality of the continuum ϕ 2 4 and ϕ 3 4 quantum field theories

We use Schwinger-Dyson equations combined with rigorous “perturbation-theoretic” correlation inequalities to give a new and extremely simple proof of the existence and nontriviality of the weakly-coupled continuum ? ₂ ⁴ and ? ₃ ⁴ quantum field theories, constructed as subsequence limits of lattice theories. We prove an asymptotic expansion to order λ or λ² for the correlation functions and for the mass gap. All Osterwalder-Schrader axioms are satisfied except perhaps Euclidean (rotation) invariance.     

Borel summability of the mass and theS-matrix in ϕ4 models

We show that in the ₂ ⁴ theory, the physical mass and the two-bodyS-matrix are Borel summable in the coupling constant at =0.     

On the ferroelectric phase transition in polytypes of β-TlInS2 crystals

Permittivity measurements and x-ray diffraction study were performed for polytypes c and 2c of β-TlInS₂ crystals in the temperature range T = 160–250 K. Substantial differences are revealed in the temperature, sequence, and character of the structural phase transitions associated with the formation of incommensurate modulated structures and the occurrence of a ferroelectric state in these polytypes.     

On the nature of the valence transition in Eu(Pd1−xAux)2Si2

The intermediate valent compound series Eu(Pd_1−xAu_x)₂Si₂ has been studied by Mössbauer effect measurements on ¹⁵¹Eu(T = 4.2−300K) and ¹⁹⁷Au (4.2K) and by X-ray diffraction (10K, 300K). The temperature induced valence transition Eu²⁺ → Eu³⁺ for x < 0.175 is not of first order type, as suggested in a previous phase diagram [1]. The valence change of the Eu-ion is reflected also in the isomer shift of the ¹⁹⁷Au Mössbauer-resonance.     

The asymmetry of the Autler－Townes doublet in a three-level system

The effect of the Bloch－Siegert shift on a strongly driven transition is studied in a three-level double-resonance configuration and the result is presented in this paper. We show that when a resonantly driven transition is probed to a third level, the Bloch－Siegert shift leads to an asymmetric Autler－Townes doublet. An important conclusion is that the asymmetry depends only on the driving field intensity, in contrast to a previous study where it is reported that the asymmetry depends not only on the driving field intensity but also on the characteristics of the three-level system. Our result implies an alternative way of measuring the Bloch－Siegert shift.     

Leading RG logs in ϕ4 theory

We find the leading RG logs in ϕ⁴ theory for any Feynman diagram with 4 external edges. We obtain the result in two ways. The first way is to calculate the relevant terms in Feynman integrals. The second way is to use the RG invariance based on the Lie algebra of graphs introduced by Connes and Kreimer.     

Effects of information asymmetry on cooperation in the prisoners’ dilemma game

Effects of information asymmetry on cooperation in the prisoners’ dilemma game are investigated. The amplitude A is introduced to describe the degree of information asymmetry. It is found that there exists an optimal value of amplitude Aopt at which the fraction of cooperation reaches its maximal value. The reason lies in that cooperators on the two-dimensional grid form large clusters at Aopt . In addition, the theoretical analysis in terms of the meanfield theory is used to understand this kind of phenomenon. It is confirmed that the information asymmetry plays an important role in the dynamics of the dilemma games of spatial prisoners.     

Effects of information asymmetry on cooperation in the prisoners＇ dilemma game

Effects of inforination asymmetry on cooperation in the prisoners＇ dilemma game are investigated. The amplitude A is introduced to describe the degree of information asymmetry. It is found that there exists an optimal value of amplitude Aopt at which the fraction of cooperation reaches its maximal value. The reason lies in that cooperators on the two-dimensional grid form large clusters at Aopt. In addition, the theoretical analysis in terms of the mean- field theory is used to understand this kind of phenomenon. It is confirmed that the information asymmetry plays an important role in the dynamics of the dilemma games of spatial prisoners.