Helicity-Dependent Cross Sections for the Photoproduction of π

The double-polarization observable E and helicity-dependent cross sections σ_{1/2}, σ_{3/2} have been measured for the photoproduction of π^{0} pairs off quasifree protons and neutrons at the Mainz MAMI accelerator with the Crystal Ball/TAPS setup. A circularly polarized photon beam was produced by bremsstrahlung from longitudinally polarized electrons and impinged on a longitudinally polarized deuterated butanol target. The reaction products were detected with an almost 4π covering calorimeter. The results reveal for the first time the helicity- and isospin-dependent structure of the γN→Nπ^{0}π^{0} reaction. They are compared to predictions from reaction models in view of nucleon resonance contributions and also to a refit of one model that predicted results for the proton and for the neutron target. The comparison of the prediction and the refit demonstrates the large impact of the new data.

Study of η and η' Photoproduction at MAMI.

The reactions γp→ηp and γp→η^{'}p are measured from their thresholds up to the center-of-mass energy W=1.96 GeV with the tagged-photon facilities at the Mainz Microtron, MAMI. Differential cross sections are obtained with unprecedented statistical accuracy, providing fine energy binning and full production-angle coverage. A strong cusp is observed in the total cross section for η photoproduction at the energies in the vicinity of the η^{'} threshold, W=1896 MeV (E_{γ}=1447 MeV). Within the framework of a revised ηMAID isobar model, the cusp, in connection with a steep rise of the η^{'} total cross section from its threshold, can only be explained by a strong coupling of the poorly known N(1895)1/2^{-} state to both ηp and η^{'}p. Including the new high-accuracy results in the ηMAID fit to available η and η^{'} photoproduction data allows the determination of the N(1895)1/2^{-} properties.

Insight into the Narrow Structure in η Photoproduction on the Neutron from Helicity-Dependent Cross Sections.

The double polarization observable E and the helicity dependent cross sections σ_{1/2} and σ_{3/2} were measured for η photoproduction from quasifree protons and neutrons. The circularly polarized tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost 4π detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from η→2γ and η→3π^{0}. The results show that the narrow structure previously observed in η photoproduction from the neutron is only apparent in σ_{1/2} and hence, most likely related to a spin-1/2 amplitude. Nucleon resonances that contribute to this partial wave in η production are only N 1/2^{-} (S_{11}) and N 1/2^{+} (P_{11}). Furthermore, the extracted Legendre coefficients of the angular distributions for σ_{1/2} are in good agreement with recent reaction model predictions assuming a narrow resonance in the P_{11} wave as the origin of this structure.

Measurements of double-polarized compton scattering asymmetries and extraction of the proton spin polarizabilities.

The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to extract the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the Δ(1232) region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields γ(E1E1)=-3.5±1.2, γ(M1M1)=3.16±0.85, γ(E1M2)=-0.7±1.2, and γ(M1E2)=1.99±0.29, in units of 10(-4) fm(4).

[Fast neutrons 6.3 MeV in the combined treatment of patients with local recurrence of breast cancer].

The article is devoted to the problem of treatment of patients with locally advanced breast cancer recurrences as well as a study of neutron therapy influence on normal tissues and various critical organs. The use of fast neutrons of 6.3 MeV in these patients is often the only treatment option. A 6-year survival rate of patients without repeated signs of recurrent breast cancer after neutron and neutron-photon therapy is 92.2 ± 5.7%.

[The use of fast neutrons in treatment of malignant tumors of the head and neck].

The article presents issues of the application of neutron therapy in the combined and radiation therapy for head and neck tumors. There were developed methods of neutron and neutron-photon therapy in pre- and postoperative periods as well as in stand-alone option in unresectable tumors. The data obtained clearly demonstrate the superiority of new ways over standard methods of treatment. Neutron therapy is satisfactorily tolerated and allows improving the results of combined and radiation therapy patients with malignant tumors of the head and neck.

[Ozone therapy for radiation reactions and skin lesions after neutron therapy in patients with malignant tumors].

The article discusses the problem of radiation complications from normal tissues in patients after therapy with fast neutrons of 6.3 MeV. The methods of treatment using ozone technologies in patients with radiation reactions and skin lesions on the areas of irradiation after neutron and neutron-photon therapy have been worked out. Ozone therapy showed its harmlessness and increased efficiency of complex treatment of these patients.

Measurement of the transverse target and beam-target asymmetries in η meson photoproduction at MAMI.

We present new data for the transverse target asymmetry T and the very first data for the beam-target asymmetry F in the γ[over →]p[over →]→ηp reaction up to a center-of-mass energy of W=1.9 GeV. The data were obtained with the Crystal-Ball/TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. All existing model predictions fail to reproduce the new data indicating a significant impact on our understanding of the underlying dynamics of η meson photoproduction. The peculiar nodal structure observed in existing T data close to threshold is not confirmed.

Neutron skin of (208)pb from coherent pion photoproduction.

Information on the size and shape of the neutron skin on (208)Pb is extracted from coherent pion photoproduction cross sections measured using the Crystal Ball detector together with the Glasgow tagger at the MAMI electron beam facility. On exploitation of an interpolated fit of a theoretical model to the measured cross sections, the half-height radius and diffuseness of the neutron distribution are found to be c(n)=6.70±0.03(stat.) fm and a(n)=0.55±0.01(stat.)(-0.03)(+0.02)(sys.) fm, respectively, corresponding to a neutron skin thickness Δr(np)=0.15±0.03(stat.)(-0.03)(+0.01)(sys.) fm. The results give the first successful extraction of a neutron skin thickness with an electromagnetic probe and indicate that the skin of (208)Pb has a halo character. The measurement provides valuable new constraints on both the structure of nuclei and the equation of state for neutron-rich matter.

Measurement of the 1H(γ, p)π0 reaction using a novel nucleon spin polarimeter.

We report the first large-acceptance measurement of polarization transfer from a polarized photon beam to a recoiling nucleon. The measurement pioneers a novel polarimetry technique, which can be applied to many other nuclear and hadron physics experiments. The commissioning reaction of 1H(γ, p)π0 in the range 0.4

Photoproduction of π0 mesons off neutrons in the nucleon resonance region.

Precise angular distributions have been measured for the first time for the photoproduction of π0 mesons off neutrons bound in the deuteron. The effects from nuclear Fermi motion have been eliminated by a complete kinematic reconstruction of the final state. The influence of final-state-interaction effects has been estimated by a comparison of the reaction cross section for quasifree protons bound in the deuteron to the results for free protons and then applied as a correction to the quasifree neutron data. The experiment was performed at the tagged photon facility of the Mainz Microtron MAMI with the Crystal Ball and TAPS detector setup for incident photon energies between 0.45 and 1.4 GeV. The results are compared to the predictions from reaction models and partial-wave analyses based on data from other isospin channels. The model predictions show large discrepancies among each other and the present data will provide much tighter constraints. This is demonstrated by the results of a new analysis in the framework of the Bonn-Gatchina coupled-channel analysis which included the present data.

[Radiation-induced reactions in breast cancer patients after breast-conserving surgery with intraoperative and external beam radiotherapy].

The present study is aimed to evaluate the frequency and severity of radiation-induced reactions in patients with stage T1-2N0-1M0 breast cancer, who received intraopeartive radiation therapy (IORT) in combination with external beam radiotherapy (EBRT). A small-size betatron producing 6 MeV electron beam was used for IORT. External beam radiotherapy was performed using Rokus and Theratron machines. Radiotherapy treatment was planned using a specially devised method to ensure acceptable levels of severity and frequency of radiation reactions. The patients were divided into 3 groups: the study (40 patients), control (88) and comparison (50) ones. Radiation-induced skin reactions in the study group ranged from erythema to moist desquamation and edema. Magnetic laser therapy was used to treat radiation-induced injuries. The applied method of estimating the total dose of IORT and EBRT was shown to provide the acceptable levels of severity and frequency of radiation reactions.

Narrow structure in the excitation function of η photoproduction off the neutron.

The photoproduction of η mesons off nucleons bound in 2H and 3He has been measured in coincidence with recoil protons and recoil neutrons for incident photon energies from threshold up to 1.4 GeV. The experiments were performed at the Mainz MAMI accelerator, using the Glasgow tagged photon facility. Decay photons from the η→2γ and η→3π0 decays and the recoil nucleons were detected with an almost 4π electromagnetic calorimeter combining the Crystal Ball and TAPS detectors. The data from both targets are of excellent statistical quality and show a narrow structure in the excitation function of γn→nη. The results from the two measurements are consistent, taking into account the expected effects from nuclear Fermi motion. The best estimates for position and intrinsic width of the structure are W=(1670±5) MeV and Γ=(30±15) MeV. For the first time precise results for the angular dependence of this structure have been extracted.

Accurate test of chiral dynamics in the γp→π0p reaction.

A precision measurement of the differential cross sections dσ/dΩ and the linearly polarized photon asymmetry Σ≡(dσ⊥-dσ∥)/(dσ⊥+dσ∥) for the γp→π0p reaction in the near-threshold region has been performed with a tagged photon beam and almost 4π detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multiphoton detector system and a cryogenic liquid hydrogen target were used. These data allowed for a precise determination of the energy dependence of the real parts of the S- and all three P-wave amplitudes for the first time and provide the most stringent test to date of the predictions of chiral perturbation theory and its energy region of agreement with experiment.

[Diagnosis of mycoplasma infections using directed amplification]. / Diagnostika mikoplazmennykh zarazhenii s pomoshch'iu napravlennoi amplifikatsii.

Test systems for rapid detection of mycoplasmas in biological samples have been elaborated on the base of the polymerase chain reaction (PCR). Amplification of the conservative rDNA sequences was used for testing of cell cultures for mycoplasmal contamination. Mycoplasma pneumoniae detection system has been developed based on amplification of the species-specific DNA sequences. Inversions of some repeated sequences in the Mycoplasma pneumoniae genome make it possible to run the PCR with a single primer. The revealed spacer length polymorphism for 16S-23S rDNA operons can be used in the mycoplasmas identification.

[Production and testing of lyophilized standard preparation for diagnosis of Mycoplasma pneumoniae infection by the indirect hemagglutination test]. / Prigotovlenie i ispytanie liofilizovannogo standartnogo preparata dlia diagnostiki v reaktsii nepriamoi gemaggliutinatsii Mikoplazmy pnevmonii.

A method for production of a reference lyophilized preparation for diagnosis of Mycoplasma pneumonia infections in the indirect hemagglutination (IHA) test has been developed. The method is based on conjugation using bi-diasotized benzidine of acrolein-treated sheep erythrocytes and ultrasonicated whole Mycoplasma antigen. After lyophilization the diagnostic preparation retained its standard properties for 1.5 years (the observation period). The sensitivity of the preparation in detection of antibody exceeded those of the CFT and the metabolism inhibition (MI) test 16--64-fold and the specificity was as good as in these tests. The diagnostic value of the preparation in the IHA was 78.1%, in the CFT--64.7%. As compared with the CFT and the MI test, the IHA with Mycoplasma diagnostic preparation is simple and reproducible.

[Humoral antiviral immunity in children with hematologic neoplasms]. / Gumoral'nyi protivovirusnyi immunitet u deteiu s onkogematologicheskimi zabolevaniiami.

Antiviral humoral immunity was studied in patients with Hodgkin's disease, idiopathic thrombocytopenic purpura (ITP), and aplastic anemia (AA). Insufficiency of antiviral humoral immunity as regards antigenically unrelated viruses and Mycoplasma pneumoniae was characteristic of all these conditions. A remission of Hodgkin's disease and ITP was associated with a reliable increase of the studied parameters in comparison with the acute period of the disease. After splenectomy humoral immunity parameters were virtually unchanged in patients with ITP, whereas in patients with Hodgkin's disease and AA the deficiency of antibody production is 40% increased after the operation.

[Characteristics of the immunologic response to Mycoplasma pneumoniae as a polyclonal lymphocyte activator]. / Osobennost' immunologicheskogo otveta na Mycoplasma pneumoniae kak na poliklonal'nyi aktivator limfotsitov.

M. pneumoniae, used as mitogen, was shown to initiate the synthesis of antibodies to salmonellae in the culture of lymphocytes obtained from healthy donors as actively as lectins and Staphylococcus aureus protein A. In these experiments IgG antibodies were mainly synthesized. The serological study of a group of persons (333 subjects) for 2.5 years revealed that seroconversion to M. pneumoniae and simultaneously to viruses occurred in 78% of cases. In more than a half of the cases a rise in the titers of antibodies to M. pneumoniae and simultaneously to salmonellae was found to occur with no cases of salmonellosis being registered. The results of this study make it possible to come to the conclusion that M. pneumoniae is a polyclonal activator of antibody-producing cells in vitro and, probably, in vivo.

[State of cellular immunity and phagocytes in guinea pigs infected with Mycoplasma pneumoniae]. / Sostoianie kletochnogo immuniteta i fagotsitov pri zarazhenii morskikh svinok Mycoplasma pneumoniae.

The work presents the results of the study of experimental Mycoplasma pneumoniae infection in guinea-pigs. A considerable increase in the engulfment of mycoplasmas and blood leukocytes was found to occur on days 14-28 after the infection. The correlation between the degree of the engulfment of mycoplasmas by macrophages and the activity of lymphocytes in the reaction of blast-cell transformation with phytohemagglutinin and Mycoplasma antigen was observed. The peculiarities of the course of infection in sensitized animals were revealed. Virulent Mycoplasma pneumoniae strains were found to have a toxic effect on the lymphocytes and macrophages of guinea-pigs. This effect was neutralized by specific antiserum. The importance of these facts for the pathogenesis of Mycoplasma infection is discussed.

[Experience with neutron teletherapy of malignant tumors]. / Opyt distantsionnoi neitronnoi terapii zlokachestvennykh opukholei.

A medico-biological complex for fast neutron therapy of cancer and research in physics and radiobiology was developed at the Siberian Branch of the Center within the framework of Cyclotron Department of Research Institute of Nuclear Physics (Polytechnical Institute, Tomsk). Certain problems of forming a fast neutron beam from the Y-120 type cyclotron are discussed. Baseline data of dosimetric and radiobiologic studies are presented. The first experience of Soviet researchers with fast neutron treatment of head and neck cancer is described. Favorable preliminary results suggest further clinical application of the said procedure.