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The ALICE Photon Spectrometer (PHOS)

PHOS (PHOton Spectrometer) is a high resolution electromagnetic calorimeter consisting of 17920 detection channels based on leadtungstate crystals (PWO).

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The Video on CDS

Phos Installed

Photo Credits: Antonio Saba

PHOS provides unique coverage of the following physics topics:

  • study initial phase of the collision of heavy nuclei via direct single photons and diphotons,
  • jet-quenching as a probe of deconfinement, studied via high pT_ and π0,
  • signals of chiral-symmetry restoration.

Technical data:

  • 17920 lead-tungstate crystals(PWO) .
  • distance to IP 4400 mm
  • coverage in pseudorapidity -0.12; +0.12
  • coverage in azimuthal angle 100°
  • crystal size 22 × 22 × 180 mm3
  • depth in radiation length 20
  • modularity 5 modules
  • total area 8 m2
  • total crystal weight 12.5 t
  • operating temperature -25°C
  • photoreadout APD

More information about the Alice PHOS