Transverse momentum spectra of \fzero in pp collisions at $\sqrt{s}=$ 13 TeV for different multiplicity classes. Each spectrum is scaled with the number shown in the figure. Statistical and systematic uncertainties are represented as bars and boxes, respectively. The normalisation uncertainty from the $\mathrm{B.R.}$ of $46\pm6$\% is not expressed in the figure. The lower panel shows the ratios of the spectra in multiplicity classes to the INEL $>$ 0 spectrum.