(K, $\pi$) invariant-mass distribution for the interval $1< \pt< 2 $ GeV/$c$ for the 0-10% (left) and 30-50% (right) centrality classes, obtained after the subtraction of the background estimated by a fourth-order polynomial function for the most central collisions and an exponential for the 30-50% centrality class. The contribution of reflections is also included in the fit. The fit function used to describe the signal (solid line) is shown.