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A study of the partial-wave content of the γp→η′p reaction in the fourth resonance region is presented, which has been prompted by new measurements of polarization observables for that process. Using the Bonn–Gatchina partial-wave formalism, the incorporation of new data indicates that the N(1895)1/2−, N(1900)3/2+, N(2100)1/2+, and N(2120)3/2− are the most significant contributors to the photoproduction process. New results for the branching ratios of the decays of these more prominent resonances to Nη′ final states are provided; such branches have not been indicated in the most recent edition of the Review of Particle Properties. Based on the analysis performed here, predictions for the helicity asymmetry E for the γp→η′p reaction are presented.

The elastic lepton–deuteron scattering was considered within the limits of zero lepton mass. The deuteron wave function in the coordinate representation for Reid93 potential was applied to numerical calculations. The angular-momentum dependence of values of the spin correlation coefficients C x z (0) , C z z (0) and tensor asymmetries A x x (0) , A x z (0) , A z z (0) were evaluated in 3D format for Reid93 potential. These polarization observables are analyzed at different energies and scattering angles. The influence of the choice of the potential model and their nodes on the calculations of the polarization observables at a fixed scattering angle was taken into account. The application of the obtained values allows better explanation and illustration of the laws for the elastic lepton–deuteron scattering. [ABSTRACT FROM AUTHOR]

Polarized response functions for beam and target polarization in the elastic electron-deuteron scattering process are investigated. We report numerical results for all the non-vanishing polarized response functions as functions of the four-momentum transfer square Q2. The sensitivity of the predicted results to the nucleon form factors is investigated. For the neutron and proton form factors, the standard dipole fit, the modified dipole fit 1, the modified dipole fit 2, and the relativistic harmonic oscillator model are used. In addition, the dependence of the results on the deuteron wave functions obtained from different modern N N potentials is studied. For this purpose, the realistic and high-precision Argonne υ18, chiral N3LO, Nijmegen-I, and CD-Bonn N N potentials are used. We found that all the non-vanishing polarized response functions are sensitive to the choices of nucleon form factors, whereas they are slightly dependent on the N N potential model adopted for the deuteron wave function. The results for all polarized response functions using the relativistic harmonic oscillator model for the nucleon form factors are found to be very small in comparison to the results of other models. [ABSTRACT FROM AUTHOR]

We report new measurements of the double-polarized photodisintegration of 3He at an incident photon energy of 16.5 MeV, carried out at the High Intensity γ-ray Source (HIγS) facility located at Triangle Universities Nuclear Laboratory (TUNL). The spin-dependent double-differential cross sections and the contribution from the three-body channel to the Gerasimov–Drell–Hearn (GDH) integrand were extracted and compared with the state-of-the-art three-body calculations. The calculations, which include the Coulomb interaction and are in good agreement with the results of previous measurements at 12.8 and 14.7 MeV, deviate from the new cross section results at 16.5 MeV. The GDH integrand was found to be about one standard deviation larger than the maximum value predicted by the theories.

Data on the polarization observables T, P, and H for the reaction γp→pπ0 are reported. Compared to earlier data from other experiments, our data are more precise and extend the covered range in energy and angle substantially. The results were extracted from azimuthal asymmetries measured using a transversely polarized target and linearly polarized photons. The data were taken at the Bonn electron stretcher accelerator ELSA with the CBELSA/TAPS detector. Within the Bonn-Gatchina partial wave analysis, the new polarization data lead to a significant narrowing of the error band for the multipoles for neutral-pion photoproduction.

Abstract Recent data on photoproduction of η ′ mesons off protons have been included in the data base for the Bonn–Gatchina partial wave analysis. The real and imaginary parts of the S -wave η ′ p → η ′ p scattering amplitude in the threshold region were fit to yield the η ′ p scattering length and the interaction range. This new analysis found | a η ′ p | = (0.403 ± 0.015 ± 0.060) fm and a phase ϕ = (87 ± 2) ∘ , while the range parameter is not well-constrained. The striking behavior of the GRAAL data on the beam asymmetry in the threshold region suggests that a narrow proton- η ′ resonance might exist. However, the scattering length was found to be relatively insensitive to the possible existence of this narrow resonance. [ABSTRACT FROM AUTHOR]

A study of the partial-wave content of the γ p → η ′ p reaction in the fourth resonance region is presented, which has been prompted by new measurements of polarization observables for that process. Using the Bonn–Gatchina partial-wave formalism, the incorporation of new data indicates that the N ( 1895 ) 1 / 2 − , N ( 1900 ) 3 / 2 + , N ( 2100 ) 1 / 2 + , and N ( 2120 ) 3 / 2 − are the most significant contributors to the photoproduction process. New results for the branching ratios of the decays of these more prominent resonances to N η ′ final states are provided; such branches have not been indicated in the most recent edition of the Review of Particle Properties. Based on the analysis performed here, predictions for the helicity asymmetry E for the γ p → η ′ p reaction are presented. [ABSTRACT FROM AUTHOR]

The reaction γ p → K ⁎ + Λ was measured using the CLAS detector for photon energies between the threshold and 3.9 GeV at the Thomas Jefferson National Accelerator Facility. For the first time, spin-density matrix elements have been extracted for this reaction. Differential cross sections, spin density matrix elements, and the Λ recoil polarization are compared with theoretical predictions using the BnGa partial wave analysis. The main result is the evidence for significant contributions from N ( 1895 ) 1 / 2 − and N ( 2100 ) 1 / 2 + to the reaction. Branching ratios for decays into K ⁎ Λ for these resonances and further resonances are reported. [ABSTRACT FROM AUTHOR]

First results from the longitudinally polarized frozen-spin target (FROST) program are reported. The double-polarization observable E , for the reaction γ → p → → π + n , has been measured using a circularly polarized tagged-photon beam, with energies from 0.35 to 2.37 GeV. The final-state pions were detected with the CEBAF Large Acceptance Spectrometer in Hall B at the Thomas Jefferson National Accelerator Facility. These polarization data agree fairly well with previous partial-wave analyses at low photon energies. Over much of the covered energy range, however, significant deviations are observed, particularly in the high-energy region where high- L multipoles contribute. The data have been included in new multipole analyses resulting in updated nucleon resonance parameters. We report updated fits from the Bonn–Gatchina, Jülich–Bonn, and SAID groups. [ABSTRACT FROM AUTHOR]

We report new measurements of the double-polarized photodisintegration of 3 He at an incident photon energy of 16.5 MeV, carried out at the High Intensity γ -ray Source (HI γ S) facility located at Triangle Universities Nuclear Laboratory (TUNL). The spin-dependent double-differential cross sections and the contribution from the three-body channel to the Gerasimov–Drell–Hearn (GDH) integrand were extracted and compared with the state-of-the-art three-body calculations. The calculations, which include the Coulomb interaction and are in good agreement with the results of previous measurements at 12.8 and 14.7 MeV, deviate from the new cross section results at 16.5 MeV. The GDH integrand was found to be about one standard deviation larger than the maximum value predicted by the theories. [ABSTRACT FROM AUTHOR]

Data on the polarization observables T , P , and H for the reaction γ p → p π 0 are reported. Compared to earlier data from other experiments, our data are more precise and extend the covered range in energy and angle substantially. The results were extracted from azimuthal asymmetries measured using a transversely polarized target and linearly polarized photons. The data were taken at the Bonn electron stretcher accelerator ELSA with the CBELSA/TAPS detector. Within the Bonn-Gatchina partial wave analysis, the new polarization data lead to a significant narrowing of the error band for the multipoles for neutral-pion photoproduction. [ABSTRACT FROM AUTHOR]

Photoproduction of two neutral pions off the proton is studied using linearly polarized photons, and the polarization observables I s and I c are measured for the first time. These two observables are unique to multi-meson final states; they characterize correlations between the linear photon polarization and the direction of outgoing single particles in photoproduction of three-body final states. The I s and I c distributions suggest that, in the 1.8 to 2.0 GeV mass region, the N ( 1520 ) 3 / 2 − π intermediate state is reached with reaction dynamics consistent with a dominant J P = 3 / 2 + wave. These data are included in the Bonn–Gatchina (BnGa) partial wave analysis which is based on a large variety of data; the analysis confirms a significant contribution from the reaction chain γ p → N ( 1900 ) 3 / 2 + → N ( 1520 ) 3 / 2 − π 0 → p π 0 π 0 . [ABSTRACT FROM AUTHOR]

The survey of cluster models used for the description of the properties of nuclei was carried out. The interaction of intermediate protons with various odd and even nuclei is reviewed. The influence of the clusterization effects on the behavior of the elastic and inelastic scattering observables are demonstrated by using multiple diffraction scattering theory (MDST) and the α-cluster model with dispersion. The comparison of the calculations, based on two- and four-nucleon correlation models, have been performed. The elastic scattering of light nuclei from α-cluster nuclei is analyzed. The results given in this review suggest that the MDST variants based on cluster models seem to be rather attractive as compared with those based on the single-nucleon approximation. Such approaches, considering nucleon and light-nuclei scattering on α-clusters, are among the best examples of using Glauber's MDST, since they automatically include the internal nucleon-nucleon correlations both in the incident and target nuclei. Besides, α-clusters have zero spin and, in this case, the scattering amplitude does not involve explicit consideration of spin-spin effects. Moreover, these models often permit an accurate analytical calculation of the MDST series. [ABSTRACT FROM AUTHOR]

This review treats the advances in Light Baryon Spectroscopy of the last two decades, which were mainly obtained by measuring meson-production reactions at photon facilities all over the world. We provide a consistent compendium of experimental results, as well as a review of the theoretical methods of amplitude analysis used to analyze the data. The most significant datasets are presented in detail and are listed in combination with a full set of the relevant references. In addition, a brief summary of spin-formalisms, which are ubiquitous in Light Baryon Spectroscopy , as well as a review on complete experiments, are provided. The synthesis of the reviewed knowledge is presented in a full interpretation of the new results on the Light Baryon Spectrum. [ABSTRACT FROM AUTHOR]

Abstract: The circular photon asymmetry for photoproduction on the proton was measured for the first time at the tagged photon facility of the MAMI C accelerator using the Crystal Ball/TAPS photon spectrometer. The experimental results are interpreted within a phenomenological isobar model that confirms the dominant role of the resonance. The measured asymmetry allows us to identify small contributions from positive-parity resonances via interference terms with the dominant amplitude. [ABSTRACT FROM AUTHOR]

To describe photo- and meson-induced reactions on the nucleon, one is faced with a rather extensive coupled-channel problem. Ignoring the effects of channel coupling, as one would do in describing a certain reaction at the tree level, invariably creates a large inconsistency between the different reactions that are described. In addition, the imaginary parts of the amplitude, which are related through the optical theorem, to total cross-sections, are directly reflected in certain polarization observables. Performing a full coupled-channel calculation thus offers the possibility to implement the maximum number of constraints. The drawback one is faced with is to arrive at a simultaneous fit of a large number of reaction channels. While some of the parameters are common to many reactions, one is still faced with the challenge to optimize a large number of parameters in a highly non-linear calculation. Here we show that such an approach is possible and present some results for photoinduced strangeness production. [ABSTRACT FROM AUTHOR]

The multiple diffraction scattering theory and the α-cluster model with dispersion have been applied for calculations of the observables for the elastic scattering of intermediate energy protons by 20Ne and 24Mg nuclei. The target nuclei are considered as composed of the core (16O nucleus) and additional α-clusters (one α-cluster for 20Ne nucleus and a dumb-bell α-cluster configuration for 24Mg nucleus). Taking into account the α-cluster configuration of the core, it was supposed that the additional α-cluster or center of mass of the dumb-bell are arranged with the most probability inside or outside of the core. The calculated observables for the elastic p–20Ne and p–24Mg scattering are in agreement with the existing experimental data. The influence of the deformed core contribution on the behavior of the calculated observables also is tested. [ABSTRACT FROM AUTHOR]

The data on the vector Ay and tensor Ayy, Axx, Axz analyzing powers for the $\overrightarrow dd \to ^3\!\!Hp$ and $\overrightarrow dd \to ^3\!\!Hen$ reactions at Ed = 200 and 270 MeV are presented. The data demonstrate large values of analyzing powers and their strong variation versus the scattering angle. The observed negative sign of the tensor analyzing powers for these reactions at small angles clearly demonstrate the sensitivity to the D/S ratio of the 3H and 3He wave functions, respectively. The calculations performed within one-nucleon exchange model with the use of the standard three-nucleon bound state wave functions fail to reproduce the data on the tensor analyzing powers. [ABSTRACT FROM AUTHOR]

Analyzing powers measurement Ay, Ayy and Axx for the d - p elastic scattering were performed at the Internal Target Station of Nuclotron at JINR at Ed = 880 and 2000 MeV. These data are necessary to obtain the information on the 3NF structure and the relativistic effects. They are also important for development of the efficient deuteron beam polarimetry at high energies. The results of the analyzing powers at Ed = 880 MeV covered the angular range from 60 to 140° in the c.m.s. are compared with several theoretical calculations. The preliminary data on the analyzing powers measurement Ay, Ayy at Ed = 2000 MeV are discussed. [ABSTRACT FROM AUTHOR]

Abstract: The photoproduction of double on the neutron is studied in the beam energy range of 0.6 up to 1.5 GeV, using a liquid deuterium target. The cross section and the beam asymmetry are extracted and compared to those previously obtained on a proton target. The theoretical interpretation of these results is given using different models. [Copyright &y& Elsevier]

The analyzing powers AN and spin correlation parameters ANN, ASS, and ASL of the elastic proton-proton scattering have been measured with an internal polarized atomic beam target at the cooler synchrotron COSY. Excitation functions were taken continuously during the acceleration and deceleration of the internal beam for kinetic energies ranging between 0.45 and 2.5 GeV and scattering angles 30° ⩽ ϴc.m ⩽ 90°. The analyzing power excitation functions provide a new polarization standard in the GeV region. The spin correlation data on ASS disagree strikingly with existing phase shift solutions. The addition of the new polarization data to the world database removes some of the ambiguities in the phase shift solutions and the direct reconstruction of scattering ambiguities. The data are compared with a recent extension of a meson-exchange potential model to higher energies. [ABSTRACT FROM AUTHOR]

The Σ beam asymmetry for positive pion photoproduction on the proton has been measured over an angular range of 40–170° at photon energies from 0.8 to 1.5 GeV. The resulting data set includes 237 accurate points, 136 of these belonging to an almost unexplored domain above 1.05 GeV. Data of such high precision provide severe constraints for partial wave analyses. The influence of this experiment on the GW multipole analysis is demonstrated. Significant changes are found in multipoles connected to the S31(1620) and P13(1720) resonances. Comparisons using the MAID analysis are also presented. [Copyright &y& Elsevier]

The differential cross section for the reaction p(γ,ηp) has been measured from threshold to 1100 MeV photon laboratory energy. For the first time, the region of the S11(1535) resonance is fully covered in a photoproduction experiment and will allow a precise extraction of its parameters at the photon point. These high precision data together with the already measured beam asymmetry data will provide stringent constraints on the extraction of new couplings of baryon resonances to the η meson. [Copyright &y& Elsevier]