The average transverse momentum of charged particles for $0.5< p_T< 4 $GeV/$c$(left panel) and $0.15< p_T< 4 $GeV/$c$ (right panel) in INEL $pp$ events at$\sqrt{s}=900 $GeV as a function of $n_{\rm ch}$ in comparison to models. The error bars and the shaded area indicate the statistical and systematic errors of the data, respectively In the lower panels, the ratio Monte Carlo over data is shown The shaded areas indicate the statistical and systematic uncertainty of the data,added in quadrature.