Abstract

This contribution will outline the physics programme exploiting the intense energy tagged polarised real photon beam at MAMI-C. The coupling of an intense photon beam and close to complete detector acceptance offers unique opportunities for preci- sion measurements to challenge our understanding of the structure of the nucleon and the nucleus as well as the underlying theory of Quantum Chromo Dynamics (QCD). The experimental facility and the physics programme will be outlined and selected recent pre- liminary analyses will be presented.

Highlights

  • The scattered electrons following this process are momentum analysed in the Glasgow-Mainz Tagger, a magnetic dipole spectrometer with a highly segmented focal plane detector array [3]

  • The scintillation light deposited in each crystal is read by its own 2 inch Photomultiplier tube (PMT)

  • The intense tagged photon beam, polarised and unpolarised targets and close to complete detector acceptance enable a rich programme of precise physics measurements to be obtained

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Summary

The MAMI-C accelerator facility

The MAMI-C[1] electron beam facility produces a 1.65 GeV high quality ∼100% duty factor electron beam from four cascaded racetrack microtrons. The scattered electrons following this process are momentum analysed in the Glasgow-Mainz Tagger, a magnetic dipole spectrometer with a highly segmented focal plane detector array [3] This provides a determination of the energy of the associated bremsstrahlung photon with a resolution of 2-3 MeV and with time resolution σt=0.117 ns. To extend the energy range of the tagged photons a new endpoint tagger (EPT) has recently been commissioned This is constructed from a new ∼1.2 T dipole magnet and associated focal plane detector array. The EPT is placed upstream of the current tagger (Fig. 2) and enables the analysis of low energy electrons associated with the higher energy photons close to the endpoint This device extends the maximum achievable tagged photon energy at MAMI-C to 1.59 GeV.

Crystal Ball
TAPS BAF2 calorimeter
The Physics programme with the Crystal Ball at MAMI
Polarisation observables in meson photoproduction
Strangeness photoproduction
Coherent pion photoproduction
Findings
Summary
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