D. Werthmueller - Crystal Ball Collaboration at MAMI

D. Werthmueller
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Name
D. Werthmueller
Affiliation
Crystal Ball Collaboration at MAMI
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Nuclear Experiment (15)
 
High Energy Physics - Phenomenology (3)
 
High Energy Physics - Experiment (3)
 
Nuclear Theory (1)

Publications Authored By D. Werthmueller

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

An experimental study of $\omega$ photoproduction on the proton was conducted by using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. The $\gamma p\to\omega p$ differential cross sections are measured from threshold to the incident-photon energy $E_\gamma=1.40$ GeV ($W=1. 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

Photoproduction of $\pi^{0}\pi^{0}$ and $\pi^{0}\pi^{\pm}$ pairs from nuclei has been measured over a wide mass range ($^2$H, $^{7}$Li, $^{12}$C, $^{40}$Ca, and $^{\rm nat}$Pb) for photon energies from threshold to 600 MeV. The experiments were performed at the MAMI accelerator in Mainz, using the Glasgow photon tagging spectrometer and a 4$\pi$ electromagnetic calorimeter consisting of the Crystal Ball and TAPS detectors. A shift of the pion-pion invariant mass spectra for heavy nuclei to small invariant masses has been observed for $\pi^0$ pairs but also for the mixed-charge pairs. 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

Coherent photoproduction of $\pi^0$-mesons from threshold ($E_{th} \approx$ 136 MeV) throughout the $\Delta$-resonance region and of $\eta$-mesons close to the production threshold ($E_{th} \approx$ 570 MeV for $\eta$) has been measured for $^7$Li nuclei. The experiment was performed using the tagged-photon beam of the Mainz MAMI accelerator with the Crystal Ball and TAPS detectors combined to give an almost 4$\pi$ solid-angle electromagnetic calorimeter. The reactions were identified by a combined invariant-mass and missing-energy analysis. 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

2010Jul
Affiliations: 1Crystal Ball Collaboration at MAMI, 2Crystal Ball Collaboration at MAMI, 3Crystal Ball Collaboration at MAMI, 4Crystal Ball Collaboration at MAMI, 5Crystal Ball Collaboration at MAMI, 6Crystal Ball Collaboration at MAMI, 7Crystal Ball Collaboration at MAMI, 8Crystal Ball Collaboration at MAMI, 9Crystal Ball Collaboration at MAMI, 10Crystal Ball Collaboration at MAMI, 11Crystal Ball Collaboration at MAMI, 12Crystal Ball Collaboration at MAMI, 13Crystal Ball Collaboration at MAMI, 14Crystal Ball Collaboration at MAMI, 15Crystal Ball Collaboration at MAMI, 16Crystal Ball Collaboration at MAMI, 17Crystal Ball Collaboration at MAMI, 18Crystal Ball Collaboration at MAMI, 19Crystal Ball Collaboration at MAMI, 20Crystal Ball Collaboration at MAMI, 21Crystal Ball Collaboration at MAMI, 22Crystal Ball Collaboration at MAMI, 23Crystal Ball Collaboration at MAMI, 24Crystal Ball Collaboration at MAMI, 25Crystal Ball Collaboration at MAMI, 26Crystal Ball Collaboration at MAMI, 27Crystal Ball Collaboration at MAMI, 28Crystal Ball Collaboration at MAMI, 29Crystal Ball Collaboration at MAMI, 30Crystal Ball Collaboration at MAMI, 31Crystal Ball Collaboration at MAMI, 32Crystal Ball Collaboration at MAMI, 33Crystal Ball Collaboration at MAMI, 34Crystal Ball Collaboration at MAMI, 35Crystal Ball Collaboration at MAMI, 36Crystal Ball Collaboration at MAMI, 37Crystal Ball Collaboration at MAMI, 38Crystal Ball Collaboration at MAMI, 39Crystal Ball Collaboration at MAMI, 40Crystal Ball Collaboration at MAMI, 41Crystal Ball Collaboration at MAMI, 42Crystal Ball Collaboration at MAMI, 43Crystal Ball Collaboration at MAMI, 44Crystal Ball Collaboration at MAMI, 45Crystal Ball Collaboration at MAMI, 46Crystal Ball Collaboration at MAMI, 47Crystal Ball Collaboration at MAMI, 48Crystal Ball Collaboration at MAMI, 49Crystal Ball Collaboration at MAMI, 50Crystal Ball Collaboration at MAMI, 51Crystal Ball Collaboration at MAMI, 52Crystal Ball Collaboration at MAMI, 53Crystal Ball Collaboration at MAMI, 54Crystal Ball Collaboration at MAMI, 55Crystal Ball Collaboration at MAMI, 56Crystal Ball Collaboration at MAMI, 57Crystal Ball Collaboration at MAMI, 58Crystal Ball Collaboration at MAMI, 59Crystal Ball Collaboration at MAMI, 60Crystal Ball Collaboration at MAMI, 61Crystal Ball Collaboration at MAMI, 62Crystal Ball Collaboration at MAMI, 63Crystal Ball Collaboration at MAMI, 64Crystal Ball Collaboration at MAMI, 65Crystal Ball Collaboration at MAMI, 66Crystal Ball Collaboration at MAMI, 67Crystal Ball Collaboration at MAMI, 68Crystal Ball Collaboration at MAMI, 69Crystal Ball Collaboration at MAMI, 70Crystal Ball Collaboration at MAMI, 71Crystal Ball Collaboration at MAMI, 72Crystal Ball Collaboration at MAMI, 73Crystal Ball Collaboration at MAMI, 74Crystal Ball Collaboration at MAMI, 75Crystal Ball Collaboration at MAMI, 76Crystal Ball Collaboration at MAMI, 77Crystal Ball Collaboration at MAMI, 78Crystal Ball Collaboration at MAMI, 79Crystal Ball Collaboration at MAMI, 80Crystal Ball Collaboration at MAMI, 81Crystal Ball Collaboration at MAMI, 82Crystal Ball Collaboration at MAMI, 83Crystal Ball Collaboration at MAMI, 84Crystal Ball Collaboration at MAMI

The gp-->etap reaction has been measured with the Crystal Ball and TAPS multiphoton spectrometers in the energy range from the production threshold of 707 MeV to 1.4 GeV (1.49 =< W >= 1. Read More