CERN Accelerating science

Schematics of the ENUBET instrumented decay tunnel. The three layers of modules of the calorimeter (light green) constitute the inner wall of the tunnel. The rings of the scintillator tiles of the photon veto (yellow) are located just below the modules. The length of each module is 10~cm and the tile doublets of the photon veto are installed every 7~cm. In the lateral readout option, the optical fibers (not shown) bring the light in the radial direction toward the outer part of the tunnel (light brown) where the SiPMs (not shown) are positioned.

Layout of the three Modules of the calorimeter. The GEANT4 simulation shows a 3 GeV electron impinging at 200 mrad the side under the calorimeter. The numbers in parenthesis correspond to the LCMs of the Modules. The $z$ direction corresponds to the axis of the tunnel. The $x$ axis correspond to the radial direction of the tunnel while $y$ cover a fraction of the azimuthal direction of the tunnel.

Layout of one LCM. The axis definition is the same as for Fig.~\ref{fig:scheme_modules}

Layout of the fibers running toward the SiPMs through several LCMs by the iron grooves. The axis definition is the same as for Fig.~\ref{fig:scheme_modules}

Mounting of one of the Modules before the bundling of the fibers and the installation of the SiPMs.

Mounting of one of the Modules before the bundling of the fibers and the installation of the SiPMs.

The full calorimeter: Module 3 (blue box) on the right, Module 2 (orange box) on the left, Module 1 behind Module 2 (not visible). The red box points out one LCM in the prototype. During the beam-test, the charged particle beam was impinging from the right and Module 1+2 were used for shower containment.

Left: fiber connector close up. Right: detail of the SiPM's connector.

Left: fiber connector close up. Right: detail of the SiPM's connector.

Four doublets of the photon veto installed below Module 3 (bottom rightmost part of the figure).

Layout of the hadronic beamline modeled with FLUKA. The regions in green are those composed of borated polyethylene.

Left: Layout of the neutron shielding above the LCMs. Right: neutron reduction induced by the borated polyethylene shielding vs the longitudinal position in the tagger. The solid line represents the neutron flux at the inner surface of the tagger while the dashed one the flux just outside of the shielding.

Left: Layout of the neutron shielding above the LCMs. Right: neutron reduction induced by the borated polyethylene shielding vs the longitudinal position in the tagger. The solid line represents the neutron flux at the inner surface of the tagger while the dashed one the flux just outside of the shielding.

Layout of the instrumentation in the T9 experimental area. The detectors installed in T9 are the Calorimeter (Module 1,2,3), two Cherenkov counters (Cher A and B), two silicon chambers (Si chambers), a muon catcher ($\mu$ catchers) and the trigger scintillator plane (Scinti). Dimensions and distances are not in scale.

Signal response to minimum ionizing particles (mip) of each LCM. The LCMs belonging to the same Module are contained in boxes. Blue (dashed line): Module 3 with Y11 fibers. Light blue (continuous line): Module 3 with BCF92 fibers. Green (dashed line) Module 2. Orange (dotted line): Module 1.

Distribution of the energy deposited in the scintillator by 3~GeV muons impinging on the front face of the calorimeter for data (red dots) and simulation (blue line).

Fiducial areas selected for the test beam data analysis obtained projecting the tracks reconstructed by the silicon chambers. Left: area selected for muon and pion (green square) and for electron (blue and green squares) responses on the front face of the calorimeter. Right: the red area represents the fiducial area selected for 100~mrad runs, where particles impinge from the lateral side of the inclined calorimeter.

Energy reconstructed in the calorimeter versus beam energy for a 100~mrad run. Testbeam data (red dots) are compared with Monte Carlo simulation including (green triangles) and not including (blue squares) the SiPM saturation. The horizontal errors correspond to the momentum bite of the beam. The vertical error bars (not visible in the plot, since of $\mathcal{O}$(0.1\%) and covered by the marker) in ``MC'' and ``Data'' are given by the standard error of the mean of the gaussian fit performed on the electron peaks. The vertical error bars in ``MC + SiPM saturation'' are given by the uncertainty on the number of pixels available to the light collection (the lowest estimate is $\sim$4580, while the highest estimate is $\sim$5400).

Energy resolution versus beam energy for particles impinging on the front face (0~mrad run) for data (red dots) and simulation (blue squares). The fit parameters for data and simulation (MC) are shown in the top and bottom insets.

Left: average energy deposited in the scintillator as a function of calorimeter planes for 3~GeV pions. Each LCM corresponds to 0.45~$\lambda_0$. Right: energy ratio between data and MC.

:

: Caption not extracted

Experimental setup for the selection of charge exchange events with converted photons. ``pm1'' and ``pm2'' are the 3$\times$3 cm$^2$ scintillator pads. VETO is the 15$\times$15 cm$^2$ pad used to veto charged particles produced after the Delrin block. The trigger is given by the coincidence of pm1 and pm2 and the anti-coincidence of VETO.

:

: Caption not extracted