0000000000096221
AUTHOR
M. Günther
Measurement of Compton scattering at MAMI for the extraction of the electric and magnetic polarizabilities of the proton
A precise measurement of the differential cross-sections $d\sigma/d\Omega$ and the linearly polarized photon beam asymmetry $\Sigma_3$ for Compton scattering on the proton below pion threshold has been performed with a tagged photon beam and almost $4\pi$ detector at the Mainz Microtron. The incident photons were produced by the recently upgraded Glasgow-Mainz photon tagging facility and impinged on a cryogenic liquid hydrogen target, with the scattered photons detected in the Crystal Ball/TAPS set-up. Using the highest statistics Compton scattering data ever measured on the proton along with two effective field theories (both covariant baryon and heavy-baryon) and one fixed-$t$ dispersion …
Postersitzung 7: Urologische Tumoren — Grundlagenforschung
Nach Ureterosigmoidostomie (UST) wurde bis 1986 uber 79 im Anastomosenbereich entstandene Adenocarcinome berichtet. Zwei entsprechende Carcinome sind im Colon-Conduit, vier im Ileum-Conduit beschrieben [6, 10]. Die Carcinomentstehung, insbesondere nach Ureterosigmoidostomie, wird meist auf eine durch gemeinsame Ableitung von Stuhl und Urin induzierte endogene Nitrosaminsynthese im Darm zuruckgefuhrt [9]. Crissey [3, 4] beschrieb 1980 in einem von ihm inaugurierten Rattenmodell in 66% eine Carcinomentstehung bei gemeinsamer Ableitung von Urin und Stuhl im Darm. Die Latenzzeit betrug 8–11 Monate. Bei Gittes [5] entstanden bei der Weiterfuhrung dieses Modells in 80% Carcinome nach 8–12 Monaten…
Neue Ergebnisse zur regionalen hyperthermen Cytostaticaperfusion tumortragender Rattenextremitäten unter besonderer Berücksichtigung der Hyperthermie
Mit Ausnahme unserer Mitteilungen uber die hypertherme Cytostatica- Perfusion tumortragender Extremitaten von Nacktratten liegen keine experimentellen Arbeiten zur Wirksamkeit dieser Form der regionalen Thermochemotherapie vor. Unsere Untersuchungen mit Melphalan ergaben keine signifikante Verlangerung der Uberlebenszeiten der Tiere, konnten jedoch einen hemmenden Einflus auf das Primartumor- und Metastasenwachstum mit langeren Uberlebenszeiten in Einzelfallen zeigen (1/ 3).
Insight into the narrow structure in η-photoproduction on the neutron from helicity\ud dependent cross sections
The double polarization observable E and the helicity dependent cross sections σ1/2 and σ3/2 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→3π0. The results show that the narrow structure previously observed in η photoproduction from the neutron is only apparent in σ1/2 and hence, most likely related to a spin-1/2 amplitude. Nucleon resonances that …
Deuteron photodisintegration by polarized photons in the region of the $d^*(2380)$
We report the first large-acceptance measurement of the beam–spin asymmetry for deuteron photodisintegration (γ→d→pn) in the photon energy range 420<Eγ<620MeV. The measurement provides important new constraints on the mechanisms of photodisintegration above the Δ resonance and on the photocoupling of the recently discovered d⁎(2380) hexaquark.
Single π0 production off neutrons bound in deuteron with linearly polarized photons
The quasifree γ→d→π0n(p) photon beam asymmetry, Σ, has been measured at photon energies, Eγ, from 390 to 610 MeV, corresponding to center of mass energy from 1.271 to 1.424 GeV, for the first time. The data were collected in the A2 hall of the MAMI electron beam facility with the Crystal Ball and TAPS calorimeters covering pion center-of-mass angles from 49∘ to 148∘. In this kinematic region, polarization observables are sensitive to contributions from the Δ(1232) and N(1440) resonances. The extracted values of Σ have been compared to predictions based on partial-wave analyses (PWAs) of the existing pion photoproduction database. Our comparison includes the SAID, MAID and Bonn–Gatchina anal…
First measurement of the polarization observable E and helicity-dependent cross sections in single π 0 photoproduction from quasi-free nucleons
The double-polarization observable $E$ and the helicity-dependent cross sections $\sigma_{1/2}$ and $\sigma_{3/2}$ have been measured for the first time for single $\pi^{0}$ photoproduction from protons and neutrons bound in the deuteron at the electron accelerator facility MAMI in Mainz, Germany. The experiment used a circularly polarized photon beam and a longitudinally polarized deuterated butanol target. The reaction products, recoil nucleons and decay photons from the $\pi^0$ meson were detected with the Crystal Ball and TAPS electromagnetic calorimeters. Effects from nuclear Fermi motion were removed by a kinematic reconstruction of the $\pi^{0}N$ final state. A comparison to data mea…
Insight into the narrow structure in {\boldmath{$\eta$}}-photoproduction on the neutron from helicity dependent cross sections
The double polarization observable $E$ and the helicity dependent cross sections $\sigma_{1/2}$ and $\sigma_{3/2}$ were measured for $\eta$ photoproduction from quasi-free 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 $4\pi$ detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from $\eta\rightarrow 2\gamma$ and $\eta\rightarrow 3\pi^0$. The results show that the narrow structure previously observed in $\eta$ photoproduction from the neutron is only apparent in $\sigma_…
Photoproduction of π 0 mesons off protons and neutrons in the second and third nucleon resonance regions
Photoproduction of mesons off quasi-free nucleons bound in the deuteron allows to study the electromagnetic excitation spectrum of the neutron and the isospin structure of the excitation of nucleon resonances. The database for such reactions is much more sparse than for free proton targets. Single $\pi^0$ photoproduction off quasi-free nucleons from the deuteron was experimentally studied. Nuclear effects were investigated by a comparison of the results for free protons and quasi-free protons and used as a correction for the quasi-free neutron data. The experiment was performed at the tagged photon beam of the Mainz MAMI accelerator for photon energies between 0.45~GeV and 1.4~GeV, using an…
Bounds on new Majoron models from the Heidelberg-Moscow experiment
In recent years several new Majoron models were invented to avoid shortcomings of the classical models while leading to observable decay rates in double beta experiments. We give the first experimental half life bounds on double beta decays with new Majoron emission and derive bounds on the effective neutrino--Majoron couplings from the data of the $^{76}Ge$ HEIDELBERG--MOSCOW experiment. While stringent half life limits for all decay modes and the coupling constants of the classical models were obtained, small matrix elements and phase space integrals \cite{hir95,pae95} result in much weaker limits on the effective coupling constants of the new Majoron models.
First measurement of helicity-dependent cross sections in Photoproduction From Quasi-free Nucleons
The helicity-dependent cross sections for the photoproduction of π0η pairs have been measured for the first time. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with the combined Crystal Ball – TAPS calorimeter. The experiment used a polarized deuterated butanol target and a circularly polarized photon beam. This arrangement allowed the σ1/2 (photon and target spin antiparallel) and σ3/2 (parallel spins) components to be measured for quasi-free production of π0η pairs off protons and neutrons. The main finding is that the two helicity components contribute identically, within uncertainties, for both participant protons and neutrons. The absolute cou…
Measurement of the beam-helicity asymmetry in photoproduction of π0η pairs on carbon, aluminum, and lead
The beam-helicity asymmetry was measured, for the first time, in photoproduction of $\pi^{0}\eta$ pairs on carbon, aluminum, and lead, with the A2 experimental setup at MAMI. The results are compared to an earlier measurement on a free proton and to the corresponding theoretical calculations. The Mainz model is used to predict the beam-helicity asymmetry for the nuclear targets. The present results indicate that the photoproduction mechanism for $\pi^{0}\eta$ pairs on nuclei is similar to photoproduction on a free nucleon. This process is dominated by the $D_{33}$ partial wave with the $\eta\Delta(1232)$ intermediate state.
Helicity-dependent cross sections and double-polarization observable E in eta photoproduction from quasi-free protons and neutrons
Precise helicity-dependent cross sections and the double-polarization observable $E$ were measured for $\eta$ photoproduction from quasi-free protons and neutrons bound in the deuteron. The $\eta\rightarrow 2\gamma$ and $\eta\rightarrow 3\pi^0\rightarrow 6\gamma$ decay modes were used to optimize the statistical quality of the data and to estimate systematic uncertainties. The measurement used the A2 detector setup at the tagged photon beam of the electron accelerator MAMI in Mainz. A longitudinally polarized deuterated butanol target was used in combination with a circularly polarized photon beam from bremsstrahlung of a longitudinally polarized electron beam. The reaction products were de…
Spin polarisation and dichroism in ARUPS from thin rare earth films
Abstract In the present study, spin polarisation and dichroism were investigated in angular resolved VUV photoemission ARUPS from magnetised as well as paramagnetic rare earth surfaces. Thin Gd(0001) films were prepared epitaxially on W(110). The photoelectrons were excited by polarised synchrotron radiation from the BESSY I synchrotron radiation source. A SPLEED detector attached to an electron spectrometer mounted on a single axis goniometer was used for angular resolved spin analysis. The main part of this work focused on the characteristic surface state of Gd(0001) which shows a splitting, as previously observed by linear magnetic dichroism and spin polarised photoemission. The spin ana…
First measurement of helicity-dependent cross sections in π0η photoproduction from quasi-free nucleons
The helicity-dependent cross sections for the photoproduction of $\pi^0\eta$ pairs have been measured for the first time. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with the combined Crystal Ball - TAPS calorimeter. The experiment used a polarized deuterated butanol target and a circularly polarized photon beam. This arrangement allowed the $\sigma_{1/2}$ (photon and target spin antiparallel) and $\sigma_{3/2}$ (parallel spins) components to be measured for quasi-free production of $\pi^0\eta$ pairs off protons and neutrons. The main finding is that the two helicity components contribute identically, within uncertainties, for both participant pr…
Signatures of the d*(2380) Hexaquark in d(γ,pn→)
We report a measurement of the spin polarization of the recoiling neutron in deuterium photodisintegration, utilizing a new large acceptance polarimeter within the Crystal Ball at MAMI. The measured photon energy range of 300-700 MeV provides the first measurement of recoil neutron polarization at photon energies where the quark substructure of the deuteron plays a role, thereby providing important new constraints on photodisintegration mechanisms. A very high neutron polarization in a narrow structure centered around E_{γ}∼570 MeV is observed, which is inconsistent with current theoretical predictions employing nucleon resonance degrees of freedom. A Legendre polynomial decomposition sugge…
Die regionale hypertherme Cytostatikaperfusion tumortragender Rattenextremitäten
Zur regionalen Cytostatikaperfusion liegen bislang einige Untersuchungen an tumortragenden Tieren unter normothermen Bedingungen vor (1, 2, 5), eine Arbeitsgruppe berichtet uber Ergebnisse nach alleiniger hyperthermer Perfusion (3). Alle Autoren beschreiben die Wirksamkeit der Perfusion anhand verschiedener Parameter. Die Untersuchungen weisen jedoch einige methodische Mangel auf und entsprechen nicht dem derzeitigen Konzept der Cytostatikaperfusion unter hyperthermen Bedingungen.