Coalescence parameter $B_2$ as a function of rapidity, for fixed transverse momentum per nucleon values. Statistical and systematic uncertainties on the data points are represented by vertical bars and boxes, respectively. The statistical uncertainties are smaller than the size of the markers in the reported scale and, hence, not visible. Bands show the model predictions from Pythia 8.3 (left panel) and from a coalescence model used as afterburner of Epos 3 (right panel), the width reflecting the statistical uncertainties.