Nuclear modification factor ($R_{cp}$) of protons and pions are investigatedby simulating Au + Au collisions from 0.8 to 1.8$A$ GeV in a framework of anisospin-dependent quantum molecular dynamics (IQMD) model. $R_{cp}$ of protonsrises with the increase of \pt~ at different beam energies owing to radial flowand Cronin effect. The rate of increase of \rcp~ is suppressed at higher beamenergies. The significant difference of $R_{cp}$ between protons and pionsindicates different medium effects between protons and pions. By changing thein-medium nucleon-nucleon cross section, the $R_{cp}$ of protons changes a lot,while the $R_{cp}$ of pions does not. Taking the pion absorption into account,the $R_{cp}$ of pions becomes close to unity without $p_{T}$ dependence afterdeactivating the reaction $\pi N \rightarrow \Delta$, while there is nearly nochange on proton. This suggests that the pion absorption plays a dominant roleon pion dynamics and have slight effect for proton dynamics.
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