Upper limit on the prompt muon flux derived from the LVD underground experiment

We present the analysis of the muon events with all muon multiplicities collected during 21804 h of operation of the first LVD tower. The measured depth-angular distribution of muon intensities has been used to obtain the normalization factor A the power index γ of the primary all-nucleon spectrum, and the ratio Rc of the prompt muon flux to that of {π} mesons---the main parameters which determine the spectrum of cosmic ray muons at the sea level. The values of γ=2.77±0.05 (68% C.L.) and Rc<2.0×10^-3 (95% C.L.) have been obtained. The upper limit to the prompt muon flux favors the models of charm production based on QGSM and the dual parton model.