A new measurement of the neutron detection efficiency for the NaI Crystal Ball detector

Pre-printWe report on a measurement of the neutron detection efficiency in NaI crystals in the Crystal Ball detector obtained from a study of single [pi][superscript 0] 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

Compton Scattering Program Studying Nucleon Polarizabilities

The A2 collaboration at the Mainz Microtron has undertaken a program of Compton scattering experiments with the goal of extracting the proton and, in the future, neutron polarizabilities. These are fundamental parameters that describe the response of the nucleon to an electromagnetic field. An extraction of these parameters will provide a crucial test of QCD theories. This talk presented the concept and status of this program, including some preliminary results

Compton Scattering Program Studying Nucleon Polarizabilities

The A2 collaboration at the Mainz Microtron has undertaken a program of Compton scattering experiments with the goal of extracting the proton and, in the future, neutron polarizabilities. These are fundamental parameters that describe the response of the nucleon to an electromagnetic field. An extraction of these parameters will provide a crucial test of QCD theories. This talk presented the concept and status of this program, including some preliminary results

Photoproduction of the omega meson on the proton near threshold

Publisher's version/PDFAn 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 [right arrow] [omega] p differential cross sections are measured from threshold to the incident-photon energy E[subscript gamma] = 1.40 GeV (W = 1.87 GeV for the center-of-mass energy) with 15-MeV binning in E[subscript gamma] and full production-angle coverage. The quality of the present data near threshold gives access to a variety of interesting physics aspects. As an example, an estimation of the [omega]N scattering length [alpha subscript omega]p is provided

T and F asymmetries in [pi superscript 0] photoproduction on the proton

Publisher's Version/PDFThe [gamma]p [right arrow] [pi superscript 0]p reaction was studied at laboratory photon energies from 425 to 1445 MeV with a transversely polarized target and a longitudinally polarized beam. The beam-target asymmetry F was measured for the first time and new high precision data for the target asymmetry T were obtained. The experiment was performed at the photon tagging facility of the Mainz Microtron (MAMI) using the Crystal Ball and TAPS photon spectrometers. The polarized cross sections were expanded in terms of associated Legendre functions and compared to recent predictions from several partial-wave analyses. The impact of the new data on our understanding of the underlying partial-wave amplitudes and baryon resonance contributions is discussed

First measurement of target and beam-target asymmetries in the gamma p -> pi 0 eta p reaction

Publisher's version/PDFThe first data on target and beam-target asymmetries for the [gamma] p [right arrow] [pi superscript 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 [superscript −] amplitude is confirmed. The data are in particular sensitive to small contributions from other partial waves

Measurement of [pi]0 photoproduction on the proton at MAMI C

Publisher's version/PDFDifferential cross sections for the [gamma]p[right arrow][pi superscript 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 superscript 0] photoproduction data by ∼47%. Owing to the unprecedented statistical accuracy and the full angular coverage, the results are sensitive to high partial-wave amplitudes. This is demonstrated by the decomposition of the differential cross sections in terms of Legendre polynomials and by further comparison to model predictions. A new solution of the SAID partial-wave analysis obtained after adding the new data into the fit is presented