Monte Carlo study of extending the BM@N tracking acceptance toward midrapidity with the Vertex Silicon Plane

Abstract

The Vertex Silicon Plane (VSP), installed close to the target in BM@N Run 9, can extend the tracking acceptance of the central tracking system toward larger polar angles. Using Monte Carlo simulations of Xe+Sn collisions at 3 AGeV, we reconstruct short tracklets from the primary vertex, one VSP hit, and hits in the first two Gas Electron Multiplier (GEM) stations. These tracklets extend the reconstructed primary-proton coverage toward midrapidity and higher transverse momenta. For the 10-30% centrality interval of the independent validation dataset, the conditional reconstruction efficiency for reconstructible high-$p_T$ primary protons after BDT selection is 67.0%, while the tracklet purity reaches 86.5%. For $p_T>1.2$ GeV/c, the VSP-assisted tracklets increase the number of reconstructed primary protons by 17.5% relative to standard BM@N tracking. Of these additional protons, 84.6% lie within $|y|<0.3$, where the relative reconstruction gain reaches 45.5%. The added acceptance is concentrated in the high-$p_T$, near-midrapidity region relevant for identified-proton observables. Its use in data requires particle identification in the same region.