Beamtest characterization of the ENUBET Demonstrator

The goal of the ENUBET project is to develop the first monitored neutrino beam, where the neutrino flux can be measured with a 1% precision, in order to carry out measurements of high precision of the neutrino cross section in the energy range of relevance for HyperKamiokande and DUNE. The systematic uncertainties are suppressed by detecting, in an instrumented decay tunnel, the large-angle leptons generated in the K+e3 three body decay (K+ -> e+pi 0 nu e). The collaboration recently completed the beamline design and tested the largest prototype of the decay tunnel: the Demonstrator. It is a sampling calorimeter composed of iron absorbers and plastic scintillators, whose light is collected by WLS fibers and readout by SiPMs. In this contribution, we discuss the characterization results obtained in the two beamtests on the PS extracted T9 beamline at CERN in 2022 and 2023. Namely the linearity and energy resolution, the effect of the optical crosstalk and a first preliminary particle identification analysis.