CERN - European Organization for Nuclear Research - Physics Department - NA62

The NA62 Detector

The ultra-rare kaon decay experiment relies on the following factors to achieve the required level of background rejection with respect to the signal channel:

  • high-resolution timing - to support a high-rate environment;
  • kinematic rejection – involving cutting on the square of the missing mass of the observed particles in the decay with respect to the incident kaon vector;
  • particle identification of kaons, pions, muons, electrons and photons;
  • hermetic vetoing of photons out to large angles and of muons within the acceptance;
  • redundancy of information.

To fulfill these purposes, the following elements and features are required to be incorporated in the layout, shown schematically above:

  1. An intense, momentum-selected hadron beam of secondary particles. The K+ component in the beam is positively identified with respect to the other beam particles by an upgraded differential Čerenkov (CEDAR) counter;
  2. The coordinates and momentum of individual beam particles are registered before entering the decay region by 3 silicon pixel tracking detectors (GTK) tracking detectors.
  3. A large-acceptance, magnetic spectrometer with tracking detectors (STRAW Tracker) in vacuum are required to detect and measure the coordinates and momentum of charged particles originating from the decay region.
  4. These are backed-up by a ring-imaging Čerenkov (RICH) counter to identify pions with respect to muons.
  5. A set of photon-veto detectors provides hermetic coverage from zero out to large (~50mr) angles from the decay region. This is assured by the existing, high-resolution, e.m. (LKR) calorimeter, supplemented, at small and forward angles, by intermediate ring (IRC) and small-angle (SAC) calorimeters and, at large angles, by a series of annular photon-veto (LAV) detectors.
  6. The LKr calorimeter is backed up by muon-veto detectors (MUV), composed of a two-part hadron calorimeter followed by additional iron and a transversally-segmented hodoscope. This system supplements and provides redundancy with respect to the RICH in the detection and rejection of muons.
  7. These detectors are complemented by ‘guard-ring’ counters (CHANTI) surrounding the last GTK station, to veto charged particles upstream of the decay region and a transversally-segmented, charged-particle hodoscope (CHOD), covering the acceptance and located between the RICH and the LKr calorimeter.
  8. All these components of the detector are inter-connected with a high-performance trigger and data-acquisition (TDAQ) system.