Performance test and commissioning of recoil detectors of HESR day-one experiment

The proposed Day-One experiment at HESR is to measure antiproton-proton elastic scattering in a large range of four momentum transfer squared t (0.0008-0.1 GeV²). One goal of the experiment is to determine the elastic differential parameters, i.e. σ_T, ρ and b. The elastic scattered antiproton and recoil proton will be measured by tracking detectors in the forward angle region and by recoil detectors near θ=90 ^circle, respectively. The recoil detectors consist of two silicon detectors and two germanium detectors which cover a polar angle from 71 ^circle to 91.5 ^circle. All detectors are single-sided structure with 1.2 mm pitch on the front side. The two silicon detectors have the same dimensions, 76.8 mm x 50.0 mm x 1.0 mm. The two germanium detectors have the same sensitive area but different thickness, 80.4 mm x 50.0 mm x 5.0 (11.0) mm. After assembling and system tests in the laboratory with radioactive source ²⁴⁴Cm, the detector system has been installed into COSY ring. The commissioning experiments by using proton beam has been performed in 2013. Data of proton-proton elastic scattering has been taken at several momenta. Preliminary data analysis indicate that the recoil detectors are working as good as expected. The latest results are presented.