Abstract
In the DsTau experiment at the CERN SPS (NA65), an independent and direct way to measure tau neutrino production following high energy proton interactions was proposed. As the main source of tau neutrinos is a decay of Ds mesons, produced in proton-nucleus interactions, the project aims at measuring a differential cross section of this reaction. The experimental method is based on a use of high resolution emulsion detectors for effective registration of events with short lived particle decays. Here we present the motivation of the study, details of the experimental technique, and the first results of the analysis of the data collected during test runs, which prove feasibility of the full scale study of the process in future.
Highlights
10 n example, in DUNE [16] and HyperKamiokande [17]) rely on νe flux measurements, but the sample of registered events is contaminated by ντ interactions due to τ → e decays
As the main source of tau neutrinos is a decay of Ds mesons, produced in proton-nucleus interactions, the project aims at measuring a differential cross section of this reaction
There were several measurements on charm particles [26,27,28,29,30], there is a lack of measurements on the Ds differential production cross section in the proton interactions, especially concerning the longitudinal dependence represented by the parameter n
Summary
Two test beam campaigns were held at CERN SPS North Area H2 and H4 beam lines, during 2016 and in 2017. Each module was mounted on a motorized X-Y stage (target mover) to change the position of the module with respect to the proton beam, so to make the detector surface uniformly irradiated at a density of 105 tracks/cm. The angular resolutions of the track segments read out by the HTS is about 2.5 mrad for the angular range relevant for DsTau. The second stage of the emulsions scanning (2) is performed at dedicated scanning stations which are very precise though not as fast as HTS. The second stage of the emulsions scanning (2) is performed at dedicated scanning stations which are very precise though not as fast as HTS In these stations, a further improvement of the resolution of the track readout in the emulsion is achieved by replacing the conventional Z-axis stage (driven by a linear rail and stepping motor) by a piezo-based Z axis (PI PIFOC R P-725.4CD ). The angular measurement reproducibility is found to be 0.16 mrad (RMS), including measurement effects (such as skewing, hysteresis, encoding resolution of X/Y axes and optical aberrations)
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