Experimental results on the excitation of isomeric nuclear states in the reactions sup.111Cd(gamma, gamma') sup.111Cd, sup.113mIn (gamma, gamma') sup.113mIn, and sup.115In (gamma, gamma') sup.115mIn ...studied by the activation method at photon energies of up to 8 MeV are presented. The respective experiments were performed at the LUE-8 linear electron accelerator of the Institute for Nuclear Research (INR, Moscow). A method for calculating cross sections per equivalent photon was developed with the aid of a simulation on the basis of the GEANT4 code. The data obtained in this way are discussed from the point of view of the possibility of studying collective nuclear excitations of various multipolarity near the threshold.
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.
A large acceptance lead-scintillator time-of-flight (TOF) wall has been developed to detect photons, neutrons, and charged particles produced in meson-photoproduction experiments on the proton and on ...the neutron. A TOF resolution of
600
ps
and a position resolution of
11×18
cm
2
(full-width at half-maximum) have been achieved. The wall has been successfully used in
η and
π
+ photoproduction experiments as a photon and a neutron detector. This paper reports its design, calibration and performance.
Experimental results on the excitation of isomeric nuclear states in the reactions
111
Cd(γ, γ′)
111
m
Cd,
113
In(γ, γ′)
113
m
In, and
115
In(γ, γ′)
115
m
In studied by the activation method at ...photon energies of up to 8 MeV are presented. The respective experiments were performed at the LUE-8 linear electron accelerator of the Institute for Nuclear Research (INR, Moscow). A method for calculating cross sections per equivalent photon was developed with the aid of a simulation on the basis of the GEANT-4 code. The data obtained in this way are discussed from the point of view of the possibility of studying collective nuclear excitations of various multipolarity near the threshold.
New experimental data on the total and partial photoabsorption cross sections on nuclei of deuterium and carbon are represented. Total cross sections are obtained by summing the partial cross ...sections for photoproduction of mesons. They are in good agreement with total cross sections obtained earlier by subtracting the background measured with an empty target. The measurements were performed at the facility GRAAL with back-scattered tagged beam γ-rays in the energy range from 700 to 1500 MeV.
New data on the fragmentation of carbon nuclei by photons with energies from 800 to 1500 MeV, obtained in the collaboration GRAAL, are presented. These data include the yields of heavier fragments ...than nucleons. Comparison of new results with literature data, obtained with real and virtual photons in reactions with electrons and relativistic ions (Coulomb dissociation) is done using a general approach in frame of the Weizsäcker–Williams model. Possible reasons for the observed differences between them are discussed.
Σ beam asymmetries for
π
+ photoproduction on the proton have been measured in the energy range 550–1100 MeV over a wide angular range. The statistical and systematic errors of the data are much ...lower than in previous measurements, due to the high polarization of the photon beam and the cylindrical geometry of the 4
π detector. Our results confirm the predictions WI98 and SM95 of the VPI partial-wave analysis at the energies below 850 MeV and at 1050 MeV while, between these two regions, they differ at backward angles. It may indicate the smaller contribution of
S
11(1650) resonance, than it was quoted previously by the VPI and PDG groups. A newly developed unitary isobar model reproduces our data up to 950 MeV.
The results of experimental studies of positron generation near the threshold carried out in 2018 at the ILC MSU femtosecond laser complex and the LUE-8 linear electron accelerator of the Institute ...for Nuclear Research of the Russian Academy of Sciences are presented. The measurements were carried out using three different detection methods: using a MEDIPIX detector; phosphor films and video cameras; as well as scintillation arrays and silicon photomultipliers.
The double polarization (beam-recoil) observables Ox and Oz have been measured for the reaction γp → K+Λ from threshold production to E ∼ 1500MeV. The data were obtained with the linearly polarized ...beam of the GRAAL facility. Values for the target asymmetry T could also be extracted despite the use of an unpolarized target. Analyses of our results by two isobar models tend to confirm the necessity to include new or poorly known resonances in the 1900MeV mass region.
Beam asymmetry and differential cross section for the reaction gamma+p->eta+p were measured from production threshold to 1500 MeV photon laboratory energy. The two dominant neutral decay modes of the ...eta meson, eta->2g and eta->3pi0, were analyzed. The full set of measurements is in good agreement with previously published results. Our data were compared with three models. They all fit satisfactorily the results but their respective resonance contributions are quite different. The possible photoexcitation of a narrow state N(1670) was investigated and no evidence was found.