Crystal Detectors in Particle Physics
- PDF / 1,970,454 Bytes
- 24 Pages / 414.72 x 648 pts Page_size
- 43 Downloads / 255 Views
ABSTRACT We review the principal characteristics driving the design of precision calorimeters composed of inorganic crystal scintillators now in operation (L3, CLEO II) or developed for the next generation of particle physics experiments. The unique discovery potential of these detectors (1.5 to 50 m 3 of crystals; 10' to > 10' elements) is the result of their high electron and photon energy resolution over a wide energy range, uniform hermetic acceptance and fine granularity. Experiments at CERN's multi-TeV Large Hadron Collider (LHC) will search for the Higgs particles thought to be responsible for mass, and for many other new physics processes. In order to exploit the intrinsically high resolution of crystal detectors, exceptionally high speed (1 to 30 ns decay time) and radiation resistance are required. BaF 2 and CeF 3 are currently the preferred choices, and higher density alternatives such as PbWO 4 are under investigation. Lower energy, high luminosity experiments that will measure rare particle decays, and explore the violation of the fundamental "CP" symmetry that may be related to the predominance of matter over antimatter in our universe, have chosen Cesium Iodide for its combination of high light output, speed, and radiation resistance. Recent developments by Caltech include the use of photons generated by an H- beam from an RFQ accelerator to calibrate and provide sub-percent resolution in the L3 BGO calorimeter, and an in situ optical bleaching technique that renders large BaF 2 crystals now mass produced in China radiation hard up to dose levels > 10 MegaRads.
INTRODUCTION The superb energy resolution and detection efficiency of total absorption shower counters composed of inorganic scintillating crystals have been known for decades. In high energy physics, the use of large arrays of scintillating crystals for the precision measurement of the energy and angle of photons and electrons has been a key factor in many of the fundamental discoveries in this field [1]. This was first demonstrated in the Crystal Ball detector's study [2] of radiative transitions and decays of the Charmonium family (Figure 1 [3]). Over the last decade, larger crystal calorimeters have been constructed, and their use has been a key factor in the successful physics programs of the L3 experiment at LEP [4], CLEO II at CESR [5] and the Crystal Barrel at LEAR [6]. Crystal detector arrays of this type also have been designed and are under development for the next generation of high energy physics experiments aimed at the study of CP violation, including KTeV at Fermilab [7]), and the SLAC [8] and KEK [9] B Factory detectors. In addition, crystal calorimeters containing 10' to more than 10' elements have been designed and studied intensively by a large sector of the high energy physics community planning experiments for multi-TeV hadron colliders, including the late Superconducting SuperCollider (SSC) in the U.S. [10,11] and the Large Hadronic Collider (LHC) at CERN in Europe [12,13]. The unique physics capability of a crystal cal
Data Loading...
