Beam-Line FIG. 3. Implementation of detectors in the πM1 area in a Geant4 [10] simulation. The beam strikes the thin scintillator beam hodoscope and three GEM chambers, passes through a hole in the annular veto scintillator, enters the cryotarget vacuum chamber and strikes one of the targets, then exits the vacuum chamber and goes through the beam monitor. Scattered particles are detected by two symmetric spectrometers, each with two straw chambers wrapped in RF shielding and two planes of scintillator paddles.

No abstract

The main aim of the study is to perform the long-term stability test of gain of the single mask triple GEM detector. A simple method is used for this longterm stability test using a radioactive X-ray source with high activity. The test is continued till accumulation of charge per unit area > 12.0 mC/mm 2 . The details of the chamber fabrication, the test set-up, the method of measurement and the test results are presented in this paper.

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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 suggests this behavior could be related to the excitation of the d à ð2380Þ hexaquark.