Promptντfluxes in present and futureτneutrino experiments

We use a nonperturbative QCD approach, the quark-gluon string model, to compute the $\tau$-neutrino fluxes produced by fixed target $\mathrm{pA}$ collisions (where $A$ is a target material) for incident protons of energies ranging from 120 to 800 GeV. The purpose of this calculation is to estimate in a consistent way the prompt background for the ${\nu }_{\mu }\left({\nu }_e\right)\leftrightarrow {\nu }_{\tau }$ oscillation search in the on-going ${\nu }_{\mu }\left({\nu }_e\right)\leftrightarrow {\nu }_{\tau }$ oscillation search experiments CHORUS and NOMAD, as well as the expected prompt background in future experiments, such as COSMOS at Fermilab and a possible second-generation ${\nu }_{\mu }\left({\nu }_e\right)\leftrightarrow {\nu }_{\tau }$ search experiment at the CERN SPS. In addition, we compute the number of ${\nu }_{\tau }$ interactions expected by the experiment E872 at Fermilab.