In situ performance of the Vertex Silicon Plane in the BM@N experiment during Run 9

Abstract

The Vertex Silicon Plane (VSP) was commissioned and operated for the first time as the most upstream tracking station of the Baryonic Matter at Nuclotron (BM@N) experiment at the NICA accelerator complex during Run 9. The station consisting of six double-sided silicon microstrip modules based on the CBM-BM@N detector technology was installed about 8 cm downstream from the target inside the SP-41 analyzing magnet. The in situ module performance was characterized in terms of the signal-to-noise ratio, time resolution, and Lorentz drift in the magnetic field. The most probable cluster signal-to-noise ratio ranges from 15.5 to 33.2, while the time resolution relative to the trigger pulse is about 12 ns. The tracking performance was evaluated using track-hit residuals and hit-matching efficiency; two independent reference configurations based on the Forward Silicon Detector (FSD) and Gas Electron Multiplier (GEM) tracking systems give consistent efficiencies of about 95%. The contribution of the VSP to the BM@N tracking performance was further studied through the transverse track impact parameter and the reconstruction of short VSP-GEM tracklets. Owing to its position close to the target and its coverage at large polar angles, the VSP provides an additional near-target tracking point and makes it possible to extend the geometrical acceptance beyond that of the FSD- and GEM-based central tracking system.