Improved Pion-Kaon Identification in Heavy-Ion Collisions with a Two-Dimensional Transformation

Abstract

Accurate identification of charged pions and kaons is essential for precision measurements in relativistic heavy-ion collisions, but becomes increasingly challenging at intermediate and high transverse momentum due to the overlap between time-of-flight mass-square ($m^{2}$) and ionization energy loss ($n\sigma$) distributions. In this work, we present a two-dimensional shift and rotation method that exploits the correlated information between $m^{2}$ and $n\sigma$ to enhance particle identification performance. The method is validated using Au+Au collision events generated with the AMPT model, where detector response effects are incorporated through a data-driven smearing procedure tuned to reproduce the particle identification performance of the STAR experiment. The reconstructed pion and kaon transverse momentum distributions show excellent agreement with the AMPT input, maintaining a purity exceeding 98\% at high $p_T$ and extend the reliable identification range up to $p_T \approx$ 3 GeV/$c$. The extracted elliptic flow $v_2$ remains consistent with the input over the extended $p_T$ range, demonstrating that the proposed method provides a robust framework for high precision identified hadron measurements.