https://doi.org/10.1140/epjc/s10052-025-14966-5
Regular Article - Experimental Physics
System size dependence of charged hadrons directed flow at 
= 200 GeV using a multi-phase transport model
1
Department of Physics, Panchayat College, 768028, Odisha, Bargarh, India
2
Instituto de Alta Investigación, Universidad de Tarapacá, Casilla 7D, 1000000, Arica, Chile
Received:
24
June
2025
Accepted:
17
October
2025
Published online:
1
November
2025
The directed flow (
) of charged hadrons (
) in symmetric collision systems (O + O, Cu + Cu, Zr + Zr, Ru + Ru, Au + Au, and U + U) at 
200 GeV using string-melting version of A Multiphase Transport (AMPT-SM) model is reported. The as a function of pseudo-rapidity (
) is obtained for transverse momentum (
) ranges of 0.2
2.0 GeV/c and 2.05.0 GeV/c. The dependence of -slope (
) at mid-rapidity on range, collision centrality, and system size are discussed particularly in the context of the hard-soft asymmetry in the flow profiles of produced particles. In the AMPT-SM model, a system size independence of the magnitude of between Cu + Cu and Au + Au collisions at low-
is observed, and this finding is similar to the observation from the STAR experiment at 200 GeV. In contrast, a strong centrality and system size dependence, with the opposite sign of , is found for the high- charged hadrons. The AMPT-SM model demonstrates a clear violation of the expected scaling of charged hadrons 
across different colliding systems.
© The Author(s) 2025
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Funded by SCOAP3.
