CERN Accelerating science

Schematic side view of the NA62 beamline and detector in 2021.

Simulated radial position of Cherenkov photons at the location of the diaphragm in \CW\ for proton (lowest radius), kaon and pion (highest radius) beam particles as a function of wavelength with \NN\ at 1.71\,bar (left panel) and \HH\ at 3.67\,bar (right panel). The quantum efficiency of the KTAG photomultiplier tubes and the transmittance of the glass filters are imposed. Dashed lines show the extent of a 2.0\,mm diaphragm aperture centred at 100\,mm.

Simulated radial position of Cherenkov photons at the location of the diaphragm in \CW\ for proton (lowest radius), kaon and pion (highest radius) beam particles as a function of wavelength with \NN\ at 1.71\,bar (left panel) and \HH\ at 3.67\,bar (right panel). The quantum efficiency of the KTAG photomultiplier tubes and the transmittance of the glass filters are imposed. Dashed lines show the extent of a 2.0\,mm diaphragm aperture centred at 100\,mm.

Sketch of the KTAG optical system (not to scale), highlighting the optical elements (green areas) and the path of Cherenkov light (blue lines).

Simulated radial position at the diaphragm of Cherenkov photons for proton, kaon and pion beam particles with \CH\ at 3.8\,bar (left panel), and as a function of wavelength (right panel). The quantum efficiency of the KTAG photomultipliers and the transmittance of the glass filters are imposed. The three distributions are normalised to the same integral. Dashed lines show the extent of a 2.0\,mm diaphragm aperture centred at 100\,mm.

Simulated radial position at the diaphragm of Cherenkov photons for proton, kaon and pion beam particles with \CH\ at 3.8\,bar (left panel), and as a function of wavelength (right panel). The quantum efficiency of the KTAG photomultipliers and the transmittance of the glass filters are imposed. The three distributions are normalised to the same integral. Dashed lines show the extent of a 2.0\,mm diaphragm aperture centred at 100\,mm.

: \CH\ under construction in a clean room at CERN. The photo shows the cylindrical gas vessel (silver-coloured part on the left of the image) and the support structure of the optical system (black part) sitting on a specialised CEDAR workbench (red part). The diaphragm can be seen at the end of the support structure on the right of the image.

: \CH\ in preparation for the test-beam on the H6 beamline at CERN.

Numbers of 6-fold, 7-fold and 8-fold coincidences per trigger as functions of diaphragm aperture at 3.85\,bar, at the H6 test-beam.

: width=0.49\textwidth

: width=0.49\textwidth : Numbers of 6-fold, 7-fold and 8-fold coincidences per trigger as functions of pressure, at a diaphragm aperture of 1.7\,mm, at the H6 test-beam. The three peaks are from the pion (lowest pressure), kaon and proton (highest pressure), shown in linear scale (left panel) and log scale (right panel). The right panel includes fits to the three peaks (dashed lines).

: height=8cm, width=0.68\textwidth

: height=8cm, width=0.30\textwidth : \CH\ (left panel) and KTAG photon-detection system (right panel) during installation in the experimental hall. In the left panel, the downstream end of \CH\ is on the left, and the black enclosure of the KTAG photon-detection system is on the right. In the right panel, the upstream-side of the enclosure is removed, revealing the eight sectors within.

Numbers of reconstructed beam particles with 5-fold, 6-fold, 7-fold and 8-fold sector coincidences per beam particle (normalised arbitrarily), as a function of diaphragm aperture at 3.88\,bar, measured using data collected with periodic triggers.

: width=0.49\textwidth

: width=0.49\textwidth : Numbers of reconstructed beam particles with 5-fold, 6-fold, 7-fold and 8-fold sector coincidences in linear scale (left panel) and log scale (right panel). The data were collected with a periodic trigger and a diaphragm aperture of 1.8\,mm, and are normalised to the measured beam intensity. The three peaks correspond to the pion (lowest pressure), kaon and proton (highest pressure). The pion peak is distorted due to limitations of the KTAG data acquisition. The right panel includes a fit to the right side of the pion peak (dashed line).

: width=0.49\textwidth

: width=0.49\textwidth : Left: number of photoelectrons per kaon candidate for \CW\ and \CH\ in the data, reconstructed with a 2\,ns time window and normalised to the same integral. Right: $K^{+}$ identification efficiency for \CW\ and \CH\ as a function of N-fold sector coincidences, with analytical expectations for the efficiency given the Poisson mean numbers of photoelectrons of 20.6 and 18.1 from fits to the distributions in the left panel.