Ratios of particle yields \kskz and \phikz as functions of \ptt  for low (X) and high (II) multiplicity classes. The middle panels show the double ratios: the measurements in class II divided by those in class X. The significance of the deviations of the double ratios from unity is plotted in the lower panels, with dashed lines indicating a deviation at the 3 $\sigma$ level. Bars represent the statistical uncertainties, while boxes represent the part of the systematic uncertainty that is uncorrelated between multiplicity classes II and X.