It should be noted that BEBC [21] and NOMAD [20] observed a discrepancy between experimental ρ rates and those estimated with JETSET [16]. NOMAD [20] proposed to retune some of the parameters used within JETSET to obtain better agreement. Therefore, for the purpose of this analysis events were simulated both with the default setting and with the setting proposed by NOMAD of key JETSET parameters, taking an average between them as a result and half a difference as a systematic error. We used experimental rates of light neutral mesons and resonances where available (Table 1) for normalization purposes. The uncertainty introduced by the JETSET parameter settings (which amounts to 20% at most) affects only the production of the η′ and ϕ for which no experimental data are available. This uncertainty is reflected in the error quoted in the table. However, since the contribution from η′ and ϕ is small, the overall effect is less important.
