M. Dieterle - A2 Collaboration at MAMI

M. Dieterle
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M. Dieterle
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A2 Collaboration at MAMI
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Nuclear Experiment (35)
 
High Energy Physics - Experiment (11)
 
Nuclear Theory (4)
 
High Energy Physics - Phenomenology (2)
 
Physics - Instrumentation and Detectors (1)

Publications Authored By M. Dieterle

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. Read More

Photoproduction of $\eta$ mesons from neutrons} \abstract{Results from measurements of the photoproduction of $\eta$ mesons from quasifree protons and neutrons are summarized. The experiments were performed with the CBELSA/TAPS detector at the electron accelerator ELSA in Bonn using the $\eta\to3\pi^{0}\to6\gamma$ decay. A liquid deuterium target was used for the measurement of total cross sections and angular distributions. Read More

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. Read More

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 $\eta\rightarrow 3\pi^0$. Read More

The reactions $\gamma p\to \eta p$ and $\gamma p\to \eta' p$ have been 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 were obtained with unprecedented accuracy, providing fine energy binning and full production-angle coverage. Read More

The Dalitz decay pi^0 -> e^+e^-gamma has been measured in the gamma p -> pi^0 p reaction with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The value obtained for the slope parameter of the pi^0 electromagnetic transition form factor, a_pi = 0.030+/-0. Read More

The scalar dipole polarizabilities, $\alpha_{E1}$ and $\beta_{M1}$, are fundamental properties related to the internal dynamics of the nucleon. The currently accepted values of the proton polarizabilities were determined by fitting to unpolarized proton Compton scattering cross section data. The measurement of the beam asymmetry $\Sigma_{3}$ in a certain kinematical range provides an alternative approach to the extraction of the scalar polarizabilities. Read More

The Dalitz decays eta -> e^+e^-g and omega -> pi^0 e^+e^- have been measured in the g p -> eta p and g p -> omega p reactions, respectively, with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The value obtained for the slope parameter of the electromagnetic transition form factor of eta, Lambda^{-2}_eta=(1.97+/-0. Read More

High statistics measurements of the photon asymmetry $\mathrm{\Sigma}$ for the $\overrightarrow{\gamma}$p$\rightarrow\pi^{0}$p reaction have been made in the center of mass energy range W=1214-1450 MeV. The data were measured with the MAMI A2 real photon beam and Crystal Ball/TAPS detector systems in Mainz, Germany. The results significantly improve the existing world data and are shown to be in good agreement with previous measurements, and with the MAID, SAID, and Bonn-Gatchina predictions. Read More

Total cross sections, angular distributions, and invariant-mass distributions have been measured for the photoproduction of $\pi^0\pi^0$ pairs off free protons and off nucleons bound in the deuteron. The experiments were performed at the MAMI accelerator facility in Mainz using the Glasgow photon tagging spectrometer and the Crystal Ball/TAPS detector. The accelerator delivered electron beams of 1508 and 1557~MeV, which produced bremsstrahlung in thin radiator foils. Read More

Photoproduction of $\pi\eta$-pairs from nucleons has been investigated from threshold up to incident photon energies of $\approx$~1.4~GeV. The quasi-free reactions $\gamma p\rightarrow p\pi^0\eta$, $\gamma n\rightarrow n\pi^0\eta$, $\gamma p\rightarrow n\pi^+\eta$, and $\gamma n\rightarrow p\pi^-\eta$ were for the first time measured from nucleons bound in the deuteron. Read More

Differential cross sections for the gamma p -> pi^0 p reaction have been measured with the A2 tagged-photon facilities at the Mainz Microtron, MAMI C, up to the center-of-mass energy W=1.9 GeV. The new results, obtained with a fine energy and angular binning, increase the existing quantity of pi^0 photoproduction data by ~47%. Read More

2015Jun
Affiliations: 1The CBELSA/TAPS Collaboration, 2The CBELSA/TAPS Collaboration, 3The CBELSA/TAPS Collaboration, 4The CBELSA/TAPS Collaboration, 5The CBELSA/TAPS Collaboration, 6The CBELSA/TAPS Collaboration, 7The CBELSA/TAPS Collaboration, 8The CBELSA/TAPS Collaboration, 9The CBELSA/TAPS Collaboration, 10The CBELSA/TAPS Collaboration, 11The CBELSA/TAPS Collaboration, 12The CBELSA/TAPS Collaboration, 13The CBELSA/TAPS Collaboration, 14The CBELSA/TAPS Collaboration, 15The CBELSA/TAPS Collaboration, 16The CBELSA/TAPS Collaboration, 17The CBELSA/TAPS Collaboration, 18The CBELSA/TAPS Collaboration, 19The CBELSA/TAPS Collaboration, 20The CBELSA/TAPS Collaboration, 21The CBELSA/TAPS Collaboration, 22The CBELSA/TAPS Collaboration, 23The CBELSA/TAPS Collaboration, 24The CBELSA/TAPS Collaboration, 25The CBELSA/TAPS Collaboration, 26The CBELSA/TAPS Collaboration, 27The CBELSA/TAPS Collaboration, 28The CBELSA/TAPS Collaboration, 29The CBELSA/TAPS Collaboration, 30The CBELSA/TAPS Collaboration, 31The CBELSA/TAPS Collaboration, 32The CBELSA/TAPS Collaboration, 33The CBELSA/TAPS Collaboration, 34The CBELSA/TAPS Collaboration, 35The CBELSA/TAPS Collaboration, 36The CBELSA/TAPS Collaboration, 37The CBELSA/TAPS Collaboration, 38The CBELSA/TAPS Collaboration, 39The CBELSA/TAPS Collaboration, 40The CBELSA/TAPS Collaboration, 41The CBELSA/TAPS Collaboration, 42The CBELSA/TAPS Collaboration, 43The CBELSA/TAPS Collaboration, 44The CBELSA/TAPS Collaboration, 45The CBELSA/TAPS Collaboration, 46The CBELSA/TAPS Collaboration, 47The CBELSA/TAPS Collaboration, 48The CBELSA/TAPS Collaboration, 49The CBELSA/TAPS Collaboration, 50The CBELSA/TAPS Collaboration, 51The CBELSA/TAPS Collaboration, 52The CBELSA/TAPS Collaboration, 53The CBELSA/TAPS Collaboration, 54The CBELSA/TAPS Collaboration, 55The CBELSA/TAPS Collaboration, 56The CBELSA/TAPS Collaboration, 57The CBELSA/TAPS Collaboration, 58The CBELSA/TAPS Collaboration, 59The CBELSA/TAPS Collaboration, 60The CBELSA/TAPS Collaboration, 61The CBELSA/TAPS Collaboration, 62The CBELSA/TAPS Collaboration, 63The CBELSA/TAPS Collaboration, 64The CBELSA/TAPS Collaboration, 65The CBELSA/TAPS Collaboration, 66The CBELSA/TAPS Collaboration, 67The CBELSA/TAPS Collaboration, 68The CBELSA/TAPS Collaboration, 69The CBELSA/TAPS Collaboration, 70The CBELSA/TAPS Collaboration, 71The CBELSA/TAPS Collaboration, 72The CBELSA/TAPS Collaboration, 73The CBELSA/TAPS Collaboration, 74The CBELSA/TAPS Collaboration, 75The CBELSA/TAPS Collaboration, 76The CBELSA/TAPS Collaboration, 77The CBELSA/TAPS Collaboration, 78The CBELSA/TAPS Collaboration, 79The CBELSA/TAPS Collaboration

Data on the polarization observables T, P, and H for the reaction $\gamma p\to p\pi^0$ 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. Read More

The first data on target and beam-target asymmetries for the $\gamma p\to\pi^0\eta p$ reaction at photon energies from 1050 up to 1450 MeV are presented. The measurements were performed using the Crystal Ball and TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. The general assumption that the reaction is dominated by the $\Delta 3/2^-$ amplitude is confirmed. Read More

We discuss the procedure of extracting the photoproduction cross section for neutral pseudoscalar mesons off neutrons from deuteron data. The main statement is that the final-state interaction (FSI) corrections for the proton and neutron target are in general not equal, but for pi0 production there are special cases were they have to be identical and there are large regions in the parameter space of incident photon energy and pion polar angle, \theta^*, where they happen to be quite similar. The corrections for both target nucleons are practically identical for $\pi_0$ production in the energy range of the Delta(1232)3/2+ resonance due to the specific isospin structure of this excitation. Read More

We report on a measurement of the neutron detection efficiency in NaI crystals in the Crystal Ball detector obtained from a study of single p0 photoproduction on deuterium using the tagged photon beam at the Mainz Microtron. The results were obtained up to a neutron energy of 400 MeV. They are compared to previous measurements made more than 15 years ago at the pion beam at the BNL AGS. Read More

We present new data for the transverse target asymmetry T and the very first data for the beam-target asymmetry F in the $\vec \gamma \vec p\to\eta p$ 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. Read More

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 measure the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the $\Delta(1232)$ region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Read More

Differential and total cross sections for the quasifree reactions $\gamma p\rightarrow\eta p$ and $\gamma n\rightarrow\eta n$ have been determined at the MAMI-C electron accelerator using a liquid deuterium target. Photons were produced via bremsstrahlung from the 1.5 GeV incident electron beam and energy-tagged with the Glasgow photon tagger. Read More

New data on the polarization observables T, P, and H for the reaction $\gamma p \to p\pi^0$ are reported. The results are extracted from azimuthal asymmetries when a transversely polarized butanol target and a linearly polarized photon beam are used. The data were taken at the Bonn electron stretcher accelerator ELSA using the CBELSA/TAPS detector. Read More

2014May
Affiliations: 1A2 Collaboration at MAMI, 2A2 Collaboration at MAMI, 3A2 Collaboration at MAMI, 4A2 Collaboration at MAMI, 5A2 Collaboration at MAMI, 6A2 Collaboration at MAMI, 7A2 Collaboration at MAMI, 8A2 Collaboration at MAMI, 9A2 Collaboration at MAMI, 10A2 Collaboration at MAMI, 11A2 Collaboration at MAMI, 12A2 Collaboration at MAMI, 13A2 Collaboration at MAMI, 14A2 Collaboration at MAMI, 15A2 Collaboration at MAMI, 16A2 Collaboration at MAMI, 17A2 Collaboration at MAMI, 18A2 Collaboration at MAMI, 19A2 Collaboration at MAMI, 20A2 Collaboration at MAMI, 21A2 Collaboration at MAMI, 22A2 Collaboration at MAMI, 23A2 Collaboration at MAMI, 24A2 Collaboration at MAMI, 25A2 Collaboration at MAMI, 26A2 Collaboration at MAMI, 27A2 Collaboration at MAMI, 28A2 Collaboration at MAMI, 29A2 Collaboration at MAMI, 30A2 Collaboration at MAMI, 31A2 Collaboration at MAMI, 32A2 Collaboration at MAMI, 33A2 Collaboration at MAMI, 34A2 Collaboration at MAMI, 35A2 Collaboration at MAMI, 36A2 Collaboration at MAMI, 37A2 Collaboration at MAMI, 38A2 Collaboration at MAMI, 39A2 Collaboration at MAMI, 40A2 Collaboration at MAMI, 41A2 Collaboration at MAMI, 42A2 Collaboration at MAMI, 43A2 Collaboration at MAMI, 44A2 Collaboration at MAMI, 45A2 Collaboration at MAMI, 46A2 Collaboration at MAMI, 47A2 Collaboration at MAMI, 48A2 Collaboration at MAMI, 49A2 Collaboration at MAMI, 50A2 Collaboration at MAMI, 51A2 Collaboration at MAMI, 52A2 Collaboration at MAMI, 53A2 Collaboration at MAMI, 54A2 Collaboration at MAMI, 55A2 Collaboration at MAMI, 56A2 Collaboration at MAMI, 57A2 Collaboration at MAMI, 58A2 Collaboration at MAMI, 59A2 Collaboration at MAMI, 60A2 Collaboration at MAMI, 61A2 Collaboration at MAMI, 62A2 Collaboration at MAMI, 63A2 Collaboration at MAMI, 64A2 Collaboration at MAMI, 65A2 Collaboration at MAMI, 66A2 Collaboration at MAMI, 67A2 Collaboration at MAMI, 68A2 Collaboration at MAMI, 69A2 Collaboration at MAMI, 70A2 Collaboration at MAMI, 71A2 Collaboration at MAMI, 72A2 Collaboration at MAMI, 73A2 Collaboration at MAMI, 74A2 Collaboration at MAMI, 75A2 Collaboration at MAMI, 76A2 Collaboration at MAMI, 77A2 Collaboration at MAMI, 78A2 Collaboration at MAMI, 79A2 Collaboration at MAMI

A new measurement of the rare, doubly radiative decay eta->pi^0 gamma gamma was conducted with the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. New data on the dependence of the partial decay width, Gamma(eta->pi^0 gamma gamma), on the two-photon invariant mass squared, m^2(gamma gamma), as well as a new, more precise value for the decay width, Gamma(eta->pi^0 gamma gamma) = (0.33+/-0. Read More

Precise angular distributions have been measured for the first time for the photoproduction of $\pi^{0}$-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 quasi-free protons bound in the deuteron to the results for free protons and then applied as a correction to the quasi-free neutron data. Read More

Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of mixed-charge pion pairs in the reactions $\boldsymbol{\gamma}p\rightarrow n\pi^0\pi^+$ off free protons and $\boldsymbol{\gamma}d\rightarrow (p)p\pi^0\pi^-$ and $\boldsymbol{\gamma}d\rightarrow (n)n\pi^0\pi^+$ off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow-Mainz magnetic spectrometer. Read More

Measurements of $\gamma p \rightarrow K^{+} \Lambda$ and $\gamma p \rightarrow K^{+} \Sigma^0$ cross-sections have been obtained with the photon tagging facility and the Crystal Ball calorimeter at MAMI-C. The measurement uses a novel $K^+$ meson identification technique in which the weak decay products are characterized using the energy and timing characteristics of the energy deposit in the calorimeter, a method that has the potential to be applied at many other facilities. The fine center-of-mass energy ($W$) resolution and statistical accuracy of the new data results in a significant impact on partial wave analyses aiming to better establish the excitation spectrum of the nucleon. Read More

2013Jun
Affiliations: 1A2 Collaboration at MAMI, 2A2 Collaboration at MAMI, 3A2 Collaboration at MAMI, 4A2 Collaboration at MAMI, 5A2 Collaboration at MAMI, 6A2 Collaboration at MAMI, 7A2 Collaboration at MAMI, 8A2 Collaboration at MAMI, 9A2 Collaboration at MAMI, 10A2 Collaboration at MAMI, 11A2 Collaboration at MAMI, 12A2 Collaboration at MAMI, 13A2 Collaboration at MAMI, 14A2 Collaboration at MAMI, 15A2 Collaboration at MAMI, 16A2 Collaboration at MAMI, 17A2 Collaboration at MAMI, 18A2 Collaboration at MAMI, 19A2 Collaboration at MAMI, 20A2 Collaboration at MAMI, 21A2 Collaboration at MAMI, 22A2 Collaboration at MAMI, 23A2 Collaboration at MAMI, 24A2 Collaboration at MAMI, 25A2 Collaboration at MAMI, 26A2 Collaboration at MAMI, 27A2 Collaboration at MAMI, 28A2 Collaboration at MAMI, 29A2 Collaboration at MAMI, 30A2 Collaboration at MAMI, 31A2 Collaboration at MAMI, 32A2 Collaboration at MAMI, 33A2 Collaboration at MAMI, 34A2 Collaboration at MAMI, 35A2 Collaboration at MAMI, 36A2 Collaboration at MAMI, 37A2 Collaboration at MAMI, 38A2 Collaboration at MAMI, 39A2 Collaboration at MAMI, 40A2 Collaboration at MAMI, 41A2 Collaboration at MAMI, 42A2 Collaboration at MAMI, 43A2 Collaboration at MAMI, 44A2 Collaboration at MAMI, 45A2 Collaboration at MAMI, 46A2 Collaboration at MAMI, 47A2 Collaboration at MAMI, 48A2 Collaboration at MAMI, 49A2 Collaboration at MAMI, 50A2 Collaboration at MAMI, 51A2 Collaboration at MAMI, 52A2 Collaboration at MAMI, 53A2 Collaboration at MAMI, 54A2 Collaboration at MAMI, 55A2 Collaboration at MAMI, 56A2 Collaboration at MAMI, 57A2 Collaboration at MAMI, 58A2 Collaboration at MAMI, 59A2 Collaboration at MAMI, 60A2 Collaboration at MAMI, 61A2 Collaboration at MAMI, 62A2 Collaboration at MAMI, 63A2 Collaboration at MAMI, 64A2 Collaboration at MAMI, 65A2 Collaboration at MAMI, 66A2 Collaboration at MAMI, 67A2 Collaboration at MAMI, 68A2 Collaboration at MAMI, 69A2 Collaboration at MAMI, 70A2 Collaboration at MAMI, 71A2 Collaboration at MAMI, 72A2 Collaboration at MAMI, 73A2 Collaboration at MAMI, 74A2 Collaboration at MAMI, 75A2 Collaboration at MAMI, 76A2 Collaboration at MAMI, 77A2 Collaboration at MAMI, 78A2 Collaboration at MAMI

The g p -> K^0 Sigma^+ reaction has been measured from threshold to Eg=1.45 GeV (W_cm=1.9 GeV) using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. Read More

Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of neutral pion pairs in the reactions $\vec{\gamma}p\rightarrow p\pi^0\pi^0$ and $\vec{\gamma}d\rightarrow (n)p\pi^0\pi^0$, $\vec{\gamma}d\rightarrow (p)n\pi^0\pi^0$ off free protons and off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow magnetic spectrometer. Read More

A precision measurement of the differential cross sections $d\sigma/d\Omega$ and the linearly polarized photon asymmetry $\Sigma \equiv (d\sigma_\perp - d\sigma_\parallel) \slash (d\sigma_\perp + d\sigma_\parallel)$ for the $\vec{\gamma} p \rightarrow \pi^0p$ reaction in the near-threshold region has been performed with a tagged photon beam and almost $4\pi$ detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multi-photon 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. Read More

There is evidence that the photoproduction of single and double pions off bound nucleons inside a nucleus are not only affected by Fermi motion but also by other nuclear effects, such as final state interactions or meson rescattering. We will present preliminary results of a high statistics measurement of single and double pion photoproduction of quasi-free protons and neutrons off the deuteron carried out at the Mainzer Microtron. Read More