Researchers have explored how the rapidity-even directed flow $v_1^{\rm even}$ of protons and antiprotons in Au+Au heavy-ion collisions can reveal details about baryon stopping. Using a (3+1)-dimensional viscous relativistic hydrodynamic model coupled to hadronic transport, the study focuses on Beam Energy Scan (BES) energies. The double-junction baryon stopping picture motivates a rapidity-even component in the baryon deposition in the initial state of the collision.

The work demonstrates that the split in the $v_1^{\rm even}$ of protons and antiprotons is particularly sensitive to the rapidity extension of the baryon deposition, which is directly associated with double-junction baryon stopping. Specifically, the mid-rapidity curvature, $\frac{d^2 \Delta v_1^{\rm even} (p-\bar{p})}{dy^2}|_{y=0}$, emerges as a robust discriminator of the initial state baryon rapidity profiles. This parameter can help distinguish between different scenarios of how baryons stop and distribute after the collision.

A simultaneous measurement of $\Delta v_1^{\rm even}$ and its curvature at mid-rapidity could constrain both the baryon diffusion strength and the baryon stopping profile. This would provide access to a deeper understanding of the underlying physics of baryon stopping in relativistic heavy-ion collisions, a crucial phenomenon for understanding the formation of the quark-gluon plasma and the properties of dense nuclear matter.