Achieving high neutron yields in today’s fusion research relies on high power auxiliary heating in order to attain required core temperatures. This is usually achieved by means of high Neutral Beam (NB) and Radio Frequency (RF) power. Application of NB power is accompanied by production of fast beam ions and associated Beam-Target (BT) reactions. In standard JET operational conditions, the latter and thermal fusion reactions are of the same order of magnitude. This study addresses important issues regarding the impact of density, central electron and ion temperatures and their ratio, Ti/Te, on the fusion performance, measured by total neutron yield and BT neutron counts. NB/RF synergistic effects are discussed as well. It is demonstrated that while thermal reactions can be extrapolated based on existing scaling expressions, the BT neutrons are more difficult to predict and this task in general would require numerical treatment. In this study BT neutrons in JET best performing baseline and hybrid pulses are analysed and underlying dependencies discussed. Central fast ions densities are found to decrease with density and density peaking. This is attributed to poorer beam penetration at high density. The BT reactions however are found to increase, and this is largely due to enhanced core temperatures. Increase in central ion temperature and Ti/Te ratio leads to higher total and BT rates as in the same time BT to total neutron ratio decreases significantly. NB/RF synergistic effects are found to have negligible impact on total neutron rate. This can be explained with reduced beam penetration in conditions of high density leading to lower central fast ions density.