Speaker
Description
With the beginning of the High Luminosity phase at the LHC (HL-LHC) at CERN, the Scattering and Neutrino Detector (SND@LHC), installed in a secondary LHC tunnel located at about 480 m distance from ATLAS interaction point, will be entirely upgraded.
The present detector design, whose signal events are interactions of neutrinos with energies mostly between 100 GeV and 1 TeV produced in the very forward direction from LHC $pp$ collisions, is based on a tungsten target equipped with nuclear emulsions and scintillating fibers, an iron-scintillator calorimeter and muon filter, and, since 2025, drift tube detectors. HL-LHC will deliver an instantaneous luminosity five times larger than the current one, and the frequency of accesses to the LHC tunnel needed to replace the emulsions before overexposure would be unmanageable.
The "Long Shutdown 3'' phase of the LHC machine will begin in July 2026. After the decomissioning of the SND@LHC experiment an entirely new detector, called SND@HL-LHC, will be installed in the same experimental area.
While the general structure of the upgrade detector is similar to the present one, including a veto region, followed by a tungsten target region and a calorimetry/muon filter section, two major changes are planned. First, both the target and calorimeter sections will be instrumented with silicon strip sensors, making SND@HL-LHC the first neutrino experiment based on silicon detectors. Second, the calorimeter will be magnetized, enabling the measurement of muon momentum and charge. Fast timing detector layers, based on small scintillating tiles read out by SiPMs, will be installed to generate a trigger signal for the readout of the silicon modules. In addition, a fast combination of information from the timing detectors and the veto layers will be used to define neutrino candidate events online. The feasibility to forward a corresponding trigger signal to ATLAS is under study.
A recently proposed design change foresees the insertion of additional silicon pixel planes, based on ALPIDE MAPS chips, used in the Inner Tracking System of the ALICE experiment. Pixel planes will help resolving ambiguities generated by the independent x-y measurements provided by silicon strips, enhancing the reconstruction of interaction vertices. In addition, a significant improvement in the muon momentum measurement is expected from the placement of two or three pixel planes at the beginning of the magnetized volume, in particular for muon tracks surrounded by hadronic shower particles. The design of pixel planes mechanics, services and readout for their installation in SND@HL-LHC is underway, together with the simulation of different placement options to study the effects on tracking, hadron shower energy and direction reconstruction, and muon momentum measurements.