Elastic Deuteron Scattering on the <Superscript>12</Superscript>C Nucleus within a Three-Body Model

The formalism developed earlier for elastic pd scattering on the basis of Glauber theory with allowance for a total spin dependence is modified by replacing pN amplitudes by amplitudes for N¹²C scattering and is applied to elastic deuteron scattering on the ¹²C nucleus. The amplitudes for elastic N¹²C scattering are obtained within the optical model. Respective numerical calculations performed at the kinetic deuteron-beam energy of 270 MeV lead to results that agree well with data on the differential cross section for d¹²C scattering into the forward hemisphere, but the calculated spin observable A _y ^d agrees with experimental data only qualitatively.     

Quasielastic rho-meson knockout from nucleons by high-energy electrons

The electroproduction of charged rho mesons on a nucleon under conditions of quasielastic kinematics [Q ² > 2 (GeV/c)², W > 3 GeV, and ω _ρ ? q ⁰ in the laboratory frame] is considered. The main diagrams involved in this process are taken into account, and it is shown that the case of rho-meson knockout by a longitudinal photon is dominated by the t-channel pole diagram featuring a rho meson, so that direct rho-meson electroknockout makes a leading contribution to the process being considered. Questions concerning the gauge invariance of the electroproduction process are considered in detail, along with contact terms that inevitably arise in employing form factors in ρNN vertices and which are necessary for restoring gauge invariance. It is shown that the structure of these contact terms is not determined exclusively by the requirement that the electroproduction amplitude be gauge-invariant and may be such that the corresponding correction to the dominant diagram due to these terms proves to be suppressed in the quasielastic region (with increasing Q ²), with the result that the t-pole process featuring a rho meson remains dominant; at the same time, the contribution of this correction is significant at low Q ² or in the case of photoproduction, modifying substantially the electroproduction cross section.     

Potential of quasielastic meson knockout from a nucleon by high-energy electrons and pions for studying the structure of exotic excited states of a final-state baryon

The possibility of studying q ⁴ \(\bar q\) exotic baryon states by means of N(e, e’M)B reactions proceeding via an extremely simple mechanism and involving the quasielastic knockout of various mesons from a nucleon by electrons of energy in the few-GeV region is considered as a development of the previous investigations of our group. A quark microscopic formalism based on the cluster model of q ⁴ \(\bar q\) states, which makes it possible to determine momentum distributions of mesons in various channels of B → N + M virtual decays (in principle, these distributions can be compared with experimental data), is expounded by considering the example of the pentaquark (B = Θ⁺). The decay widths of the q ⁴ \(\bar q\) baryon states being discussed are governed by the degree of separation of quark clusters (this is a parameter of the model used). The electroproduction cross sections prove to be small because of kinematical constraints requiring that physically admissible values of the momentum ‖k‖ of the virtual meson M lie in the region where relevant amplitudes are suppressed substantially by form factors in pentaquark vertices. In particular, N (e, e′π ^±)B reactions involving pion knockout furnish direct information about nonstrange components of baryon B; however, the expected cross sections for such reactions are an order of magnitude smaller than their counterparts for analogous reactions leading to the production of a pentaquark Θ⁺. Because of the smallness of the electroproduction cross sections, it is reasonable to consider the production of a pentaquark and other q ⁴ \(\bar q\) exotic states in reactions characterized by quasielastic kinematics and initiated by pions of energy in the range between about 1 and 5 GeV and in similar stripping and pickup nuclear reactions.     

Correlation between the properties of the deuteron and the low-energy triplet parameters of neutron-proton scattering

The correlation between the asymptotic normalization constant for the deuteron, A_S, and the neutron-proton scattering length for the triplet case, a_t, is investigated. It is found that 99.7% of the asymptotic constant A_S is determined by the scattering length a_t. It is shown that the linear correlation between the quantities A _S ^?2 and 1/a_t provides a good test of correctness of various models of nucleon-nucleon interaction. It is revealed that, for the normalization constant A_S and for the root-mean-square deuteron radius r_d, the results obtained with the experimental value recommended at present for the triplet scattering length a_t are exaggerated with respect to their experimental counterparts. By using the latest experimental data obtained for phase shifts by the group headed by Arndt, it proved to be possible to derive, for the low-energy parameters of scattering (a_t, r_t, P_t) and for the properties of the deuteron (A_S, r_d) results that comply well with experimental data.     

Messung der Protonenpolarisation bei der Reaktion C12(d,p) C13 für Deuteronenenergien zwischen 0,8 und 1,2 MeV

The energy dependence of the proton polarizationP has been measured for a fixed reaction angle of 52 degrees by p-He⁴ elastic scattering.P varies rapidly with the deuteron energyE _d . The experimental results are in good agreement with the assumption of aJ ^π = 1^? level of the compound nucleus N¹⁴ at 11,23 MeV (E _d = 1,13 MeV).     

Investigation of <Emphasis Type="Italic">pn</Emphasis> correlations in <Superscript>4</Superscript>He<Emphasis Type="Italic">p</Emphasis> interactions at a momentum of 5 GeV/<Emphasis Type="Italic">c</Emphasis>

Proton-neutron correlations in ⁴Hep interactions are studied in an exclusive experiment by using a 2-m bubble chamber exposed to a 5-GeV/c beam of α particles (the kinetic energy of the protons in the nucleus rest frame is T _p = 620 MeV). Data on the production of pn pairs in 4π geometry for three channels, where it is possible to reconstruct the neutron momentum unambiguously, are used to determine the pn correlation function in ⁴Hep interactions. The experimental results are compared with the predictions of a modified Lednicky-Lyuboshitz model. The value obtained for the root-mean-square radius of the pn-emission region is R _pn = 2.1 ± 0.3 fm. The dependence of the correlation function on the modulus of the total momentum of the emitted nucleon pair and on the direction of the momentum transfer is studied. An indication that the emission of a pn pair proceeds predominantly through the production of a virtual deuteron is obtained.     

First evidence for a Sm<Superscript>3+</Superscript>-type contribution to the magnetic form factor in the quasielastic spectral response of intermediate valence SmB<Subscript>6</Subscript>

The momentum-transfer dependence of the magnetic form factor associated with the quasielastic spectral component in the dynamic magnetic response of intermediate valence SmB₆ has been measured using inelastic neutron scattering on a double-isotope (¹⁵⁴Sm, ¹¹B) single crystal. The experimental dependence differs qualitatively from those obtained earlier for the inelastic signals, as well as from the field-induced magnetic form factor of SmB₆ obtained by polarized neutron diffraction. This observation is interpreted by specifically considering the Curie-type contributions to the dynamic susceptibility, which arise from the mixing of 4 f⁵ and 4 f⁶J-multiplets into the intermediate valence state wavefunction.     

Pseudogap and its temperature dependence in YBCO from the data of resistance measurements

The temperature dependence of the excess conductivity Δσ for Δσ = A(1 ? T/T^*)exp(Δ^*/T) (YBCO) epitaxial films is analyzed. The excess conductivity is determined from the difference between the normal resistance extrapolated to the low-temperature range and the measured resistance. It is demonstrated that the temperature dependence of the excess conductivity is adequately described by the relationship Δσ = A(1 ? T/T^*)exp(Δ^*/T). The pseudogap width and its temperature dependence are calculated under the assumption that the temperature behavior of the excess conductivity is associated with the formation of the pseudogap at temperatures well above the critical temperature T _c of superconductivity. The results obtained are compared with the available experimental and theoretical data. The crossover to fluctuation conductivity near the critical temperature T _c is discussed.     

Elastische und unelastische Streuung von Deuteronen an Aluminium bei 11,8 MeV

Using the 11.8 MeV deuteron beam of a cyclotron, a study has been made of the angular dependence of the deuteron spectrum from interactions on Al²⁷. Separation of the deuterons from other products of the deuteron reactions was accomplished by recordingdE/dx, measured by a three fold proportional counter, andE, measured by a CsI-counter, on an oscilloscope screen. The experimental inelastic angular distributions have the shape of a direct interaction process. The elastic angular distribution shows pronounced diffraction maxima.     

Single and double spin asymmetries in the elastic <Emphasis Type="Italic">e</Emphasis>-<Emphasis Type="Italic">d</Emphasis> scattering and their dependence on the deuteron wave function

Single and double spin asymmetries in the elastic electron-deuteron (e-d ) scattering were investigated. The tensor-deuteron asymmetries T_2i(i = 0, 1, 2) and the beam-vector-deuteron asymmetries T ^e _1i(i = 0, 1) were calculated and compared with the available experimental data. The sensitivity of the results for these spin asymmetries to the deuteron wave function has been investigated. The predicted asymmetries were found to be agree with one another and with experiment. It was found that, the double spin asymmetry T ^e ₁₀ is much smaller than the T ^e ₁₁-asymmetry. Therefore, in addition to the single tensor-deuteron asymmetry T₂₀, the doubly beam-vector-deuteron asymmetry T ^e ₁₁ can be used as an another tool for extracting the deuteron electromagnetic form factors.     

Antiferromagnetic Resonance in GdB<Subscript>6</Subscript>

The electron spin resonance has been measured for the first time both in the paramagnetic phase of the metallic GdB₆ antiferromagnet (T_N = 15.5K) and in the antiferromagnetic state (T < T_N). In the paramagnetic phase below T* ~ 70 K, the material is found to exhibit a pronounced increase in the resonance linewidth and a shift in the g-factor, which is proportional to the linewidth Δg(T) ~ ΔH(T). Such behavior is not characteristic of antiferromagnetic metals and seems to be due to the effects related to displacements of Gd³⁺ ions from the centrosymmetric positions in the boron cage. The transition to the antiferromagnetic phase is accompanied by an abrupt change in the position of resonance (from μ₀H₀ ≈ 1.9 T to μ₀H₀ ≈ 3.9 T at ν = 60 GHz), after which a smooth evolution of the spectrum occurs, resulting eventually in the formation of the spectrum consisting of four resonance lines. The magnetic field dependence of the frequency of the resonant modes ω₀(H₀) obtained in the range of 28–69 GHz is well interpreted within the model of ESR in an antiferromagnet with the easy anisotropy axis ω/γ = (H ₀ ² +2H_AH_E)^1/2, where H_E is the exchange field and H_A is the anisotropy field. This provides an estimate for the anisotropy field, H_A ≈ 800 Oe. This value can result from the dipole?dipole interaction related to the mutual displacement of Gd³⁺ ions, which occurs at the antiferromagnetic transition.     

Role of the nuclear and electromagnetic interactions in the coherent dissociation of the relativistic <Superscript>7</Superscript>Li nucleus into the <Superscript>3</Superscript>H + <Superscript>4</Superscript>He channel

The differential cross section in the transverse momentum Q and a total cross section of (31 ± 4) mb for the coherent dissociation of a 3-A-Ge V/c ⁷Li nucleus through the ³H + ⁴He channel have been measured on emulsion nuclei. The observed Q dependence of the cross section is explained by the predominant supposition of the nuclear diffraction patterns on light (C, N, O) and heavy (Br, Ag) emulsion nuclei. The contributions to the cross section from nuclear diffraction (Q ≤ 400 Me V/c) and Coulomb (Q ≤ 50 Me V/c) dissociations are calculated to be 40.7 and 4 mb, respectively.     

Measurement of polarization angular coefficients in <Emphasis Type="Italic">Z</Emphasis> boson leptonic decays with ATLAS at the LHC

This paper presents the complete set of polarization angular coefficients A _0?7 describing lepton angular distributions in Z boson decay, which were measured at the ATLAS experiment in proton–proton collisions with the energy √s = 8 TeV. Theoretical values for the difference A ₀ ? A ₂ calculated in the fixed-order QCD perturbation theory O(α _s ² ), demonstrate significant deviation from the measured data, which indicates the necessity of taking into account higher order corrections. The evidence of nonzero coefficients A _5,6,7 was obtained for the first time, in accordance with theoretical calculations in O(α _s ² ) approximation. Measurement of the polarization angular coefficients A _i is important for subsequent precision measurement of parameters of the electroweak model at the LHC, such as the sine of Weinberg electroweak mixing angle sin² θ _W and the W boson mass.     

Microscopics of mesonic degrees of freedom in nucleons and mesons in nuclei: Quasielastic meson knockout by high-energy electrons

The following questions are considered: (i) that of what quasielastic-knockout reactions are; (ii) that of what experience has been gained in measuring, in various channels, the momentum distributions and spectroscopic factors of nucleons and clusters in nuclei and of electrons in atoms, molecules, and solid-state bodies; (iii) that of how it is possible to introduce the concept of quasielastic knockout in the theory of meson-electroproduction processes p(e, e′m)B at beam energies of a few GeV and at moderate values of the square of the virtual-photon 4-momentum, Q ² = 2–4 (GeV/c)²; and (iv) that of how the momentum distributions of mesons in various channels of virtual proton decay, p → B + π, p → B + ρ, and p → Y + K, are predicted on the basis of the microscopic model of a fluctuation of the QCD vacuum in a nucleon. Proposals for relevant experiments are formulated. It is indicated that quasielastic-knockout processes like (e, e′π) provide the best way to study the problem of a scalar pion condensate in nuclei. In conclusion, it is emphasized that quasielastic processes ²H(e, e′p)B involving various spectator baryons B are of great value for determining the composition of multiquark configurations in nucleon-nucleon systems.     

Observation of coherent <Emphasis Type="Italic">π</Emphasis><Superscript>0</Superscript> electroproduction on deuterons at large momentum transfer

The first experimental results for the coherent π⁰ electroproduction on a deuteron, e+d → e+d+π⁰, at large momentum transfer, are reported. The experiment was performed at Jefferson Laboratory at an incident electron energy of 4.05 GeV. A large pion production yield has been observed in the kinematical region 1.1<Q²<1.8 GeV², from the threshold to 200-MeV excitation energy in the dπ⁰ system. The Q² dependence is compared with theoretical predictions.     

Polarization observables <Emphasis Type="Italic">P</Emphasis> + <Emphasis Type="Italic">A</Emphasis> and (<Emphasis Type="Italic">P</Emphasis> + <Emphasis Type="Italic">A</Emphasis>)σ in 200-MeV proton inelastic scattering

Experimental and calculated data on inelastic scattering of polarized protons are presented as polarization-analyzing-power combinations P + A and (P + A)σ for the 0⁺ → 1⁺, T = 1 transition in ¹²C. Data on the polarization P and the function (P ? A)σ are also reported. Microscopic calculations have been performed using the DWBA program with the G-matrix interaction based on the Paris and Bonn potentials. A significant difference between the effective interaction with density correction and free NN interaction has been demonstrated. It is established that the (P + A)σ combination is especially sensitive to systematic variations in the density dependence in effective NN interactions.     

Theory of the muonic hydrogen-muonic deuterium isotope shift

Corrections of the α³, α⁴, and α⁵ orders are calculated for the Lamb shift of the 1S and 2S energy levels of muonic hydrogen μp and muonic deuterium μd. The nuclear structure effects are taken into account in terms of the charge radii of the proton r _p and deuteron r _d for one-photon interaction, as well as in terms of the electromagnetic form factors of the proton and deuteron for the case of one-loop amplitudes. The μd-μp isotope shift for the 1S-2S splitting is found to be equal to 101003.3495 meV, which can be treated as a reliable estimate when conducting the corresponding experiment with an accuracy of 10^?6. The fine-structure intervals E(1S)-8E(2S) in muonic hydrogen and muonic deuteron are calculated.     

Study of collective flow effects in CC collisions at a momentum of 4.2 GeV/<Emphasis Type="Italic">c</Emphasis> per nucleon

Directed (in-plane) flows of protons, pions, and projectile light fragments (d, t, ³He, ⁴He) have been observed by investigating the dependence of the mean transverse momentum in the reaction plane 〈p _x 〉 on the rapidity y in the c.m. system for CC collisions at a momentum of 4.2 GeV/c per nucleon. The comparison of our in-plane-flow results of protons with flow data for various projectile/target configurations was made using the scaled flow F _s = F/(A _P ^1/3 + A _T ^1/3 ). F _s demonstrates a common scaling behavior for flow values from different systems. From azimuthal distributions of protons and π^? mesons, out-of-plane (squeeze-out) flow effects have been observed and the parameter a₂ (the measure of the anisotropic emission strength) has been extracted. The quark-gluon string model reproduces the experimental results quite well.     

Quark microscopic picture for vector and pseudoscalar mesons in the nucleon and their quasielastic knockout by high-energy electrons

A technique for projecting a multiquark wave function in the microscopic model of a ³P⁰ scalar fluctuation onto the virtual-decay channels N → N + ρ and N → N + π is formulated (at a more general level for the latter than previously). The amplitude for the electromagnetic transition ρ + γ _T ^* → π in electron-induced quasielastic rho-meson knockout followed by rho-meson conversion to a pion is considered. Theoretical results obtained in this way are contrasted against available experimental data, and reasonable agreement is found for cross-section values. This confirms a universal character of the ³P₀ model. The precision of relevant experiments is as yet insufficient for comparing the momentum distribution of the rho meson from the channel N → N + ρ with its theoretical counterpart.     

Modified multicomponent band pass optical reflection filters at oblique incidence

Reflection and transmission characteristics of a modified long-wavelength cutoff filter using a three-component system with an angular dependence are studied. In this case, a layer of high refractive index is sandwiched between edge layers of equivalent refractive index with the base structure [G(0.5AB0.5A)]^N; then, an optimized structure of the form [(0.5AB0.5A)^N?X (0.5AB0.5A)^X (0.5AB0.5A)^N?X] is taken and its spectral properties are studied. In the case of a short-wavelength three-component cutoff filter, a layer of low refractive index is sandwiched between two edge layers of high equivalent refractive index with a base structure [G(0.5BA0.5D)]^N and its spectral characteristics are studied. Then, the structure is optimized [(0.5BA0.5B)^{N? X}(0.5BA0.5B)^X(0.5BA0.5B)^N?tX] and spectral characteristics of this structure are also studied. Spectral properties of band pass optical reflection filters of the type [G(XY)A] whose components are the proposed long-wavelength cutoff [(0.5AB0.5B)^{N? X}(0.5AB0.5A)^X(0.5BA0.5B)^N?X] and short-wavelength cutoff [(0.5BA0.5B)^N?X(0.5BA0.5B)^X(0.5BA0.5B)^N?X] filter structures are studied with angular dependences. No increase in the bandwidth with the least oscillatory components at the edges can be precisely formed by known classes of a two-component system at normal incidence. It is shown that the use of reflection and transmission filters with oblique bands yields an ideal polarizer. Angular dependences of the filter and the transmission and reflection band shapes on the parameters of a high-reflectance multilayer coating, such as the thickness, refractive indices, and the number of layers, are analyzed in detail.