The UI group has built two of the scintillator arrays placed at the end of the FOCUS spectrometer which is used to identify muons.

• The two UI arrays are labeled MH1 and MH2.
  • The MH1 array consists of 84 vertical and 126 horizontal counters.
  • The MH2 array consists of 52 vertical and 78 horizontal counters.
  • The MH3 array built by our colleagues at University of Puerto Rico consist of 54 counters at + 45 degrees and 54 counters at - 45 degrees.
• Muon are shielded by about 15 absorption lengths of iron which absorb all charged particles from charm decay but muons.
• The use of scintillation counters allows for very crisp (1 Rf bucket) timing.
• Fine granularity is used in order to uniquely match tracks to muon hits to the extent allowed by multiple Coulomb scattering
• Here is a schematic of the MH1 array