The CALICE hadron calorimeters - test beam results

We present concepts and beam test results of highly granular calorimeter prototypes optimized for the application of particle flow algorithms. A scintillator-steel hadron calorimeter using SiPMs as photodetectors (AHCAL) has been tested in electron and hadron beams at CERN and Fermilab in the energy range 1 – 80 GeV. More than 7600 SiPMs – the highest number ever used – performed well over the period longer than 2 years and did not show an increase of noise. The analysis of the first part of data from hadron beams leads to the energy resolution of 61%/√E which can be further improved to 49%/√E applying energy dependent weights. The data on the longitudinal and transverse shower shapes allow discriminate among hadronization models of GEANT4. Specifically QGSP_BERT and LHEP prediction were compared to the data. Further we present the concept of a Digital Hadron Calorimeter (DHCAL) with two lines of R&D following different read-out and integration approach. Both are based on glass resistive pad chambers with 1 cm pad read-out, alternative amplification techniques like GEMs or MICROMEGAS are also being considered. One series of studies applies a single threshold (1bit) to the signal charges, providing digital readout with the front end part integrated on the pad board. We report on the measurements with a small scale prototype in the Fermilab test beam using muons, positrons, pions, and protons and in the laboratory using cosmic rays. An alternative approach is to use semi-digital readout electronics following a design close to the ILD detector concept. The electronics will not require active cooling and rely on power-pulsing. A small prototype was built and tested with success at the CERN PS test beam in 2008. A few GRPCs as large as 1 m were built with emphasis on minimized dead zones and optimized gas flow. The GRPCs were tested with an electronics board of the same size, containing 144 64channel ASICs, representing the largest ever built chamber with embedded electronics. The results will serve as the basis for the design of the fully instrumented 1 m CALICE test beam digital calorimeter.