Design, commissioning and performance of the PIBETA detector at PSI

E. Frlež, D. Počanić, K. A. Assamagan, Yu Bagaturia, V. A. Baranov, W. Bertl, Ch Brönnimann, M. Bychkov, J. F. Crawford, M. Daum, Th Flügel, R. Frosch, R. Horisberger, V. A. Kalinnikov, V. V. Karpukhin, N. V. Khomutov, J. E. Koglin, A. S. Korenchenko, S. M. Korenchenko, T. KozlowskiB. Krause, N. P. Kravchuk, N. A. Kuchinsky, W. Li, D. W. Lawrence, R. C. Minehart, D. Mzhavia, H. Obermeier, D. Renker, Barry Ritchie, S. Ritt, T. Sakhelashvili, R. Schnyder, V. V. Sidorkin, P. L. Slocum, L. C. Smith, N. Soić, W. A. Stephens, I. Supek, Z. Tsamalaidze, B. A. VanDevender, Y. Wang, H. P. Wirtz, K. O H Ziock

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


We describe the design, construction and performance of the PIBETA detector built for the precise measurement of the branching ratio of pion beta decay, π+→π0e+νe, at the Paul Scherrer Institute. The central part of the detector is a 240-module spherical pure CsI calorimeter covering ∼3π sr solid angle. The calorimeter is supplemented with an active collimator/beam degrader system, an active segmented plastic target, a pair of low-mass cylindrical wire chambers and a 20-element cylindrical plastic scintillator hodoscope. The whole detector system is housed inside a temperature-controlled lead brick enclosure, which in turn is lined with cosmic muon plastic veto counters. Commissioning and calibration data were taken during two 3-month beam periods in 1999/2000 with π+ stopping rates between 1.3·103 π+/s and 1.3·106 π+/s. We examine the timing, energy and angular detector resolution for photons, positrons and protons in the energy range of 5-150 MeV, as well as the response of the detector to cosmic muons. We illustrate the detector signatures for the assorted rare pion and muon decays and their associated backgrounds.

Original languageEnglish (US)
Pages (from-to)300-347
Number of pages48
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Issue number3
StatePublished - Jul 1 2004


  • Calibration and performance
  • Construction
  • Detector design
  • Large acceptance segmented calorimeter
  • Pure CsI scintillators
  • Tracking and particle identification

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Instrumentation


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