FoCal pad prototype and its test results

A new forward calorimeter (FoCal) covering 3.4 < η < 5.8 is being developed as a possible detector upgrade of the ALICE experiment at LHC . FoCal will be a unique detector with a Si+W electromagnetic calorimeter (FoCal-E) and a conventional sampling hadronic calorimeter (FoCal-H), and the installation of and data taking with FoCal are expected during the LHC Long Shutdown 3 (in 2025-2027) and Run 4 (in 2027–2029), respectively. A prototype module, called "mini-FoCal", was built and tested in 2018. 60 silicon pad sensors were used to produce 20 layers in total with a size of 281.0 mm by 96.0 mm and a thickness of 5.5 mm. The first beam test with the mini-FoCal was carried out at the CERN PS and SPS complexes in 2018. Electromagnetic shower signals were successfully measured in addition to the MIP peak for calibration. A good signal-to-noise ratio was confirmed and the energy resolution of the mini-FoCal was estimated to be Δ E / E = 4.1% ± 0.5% for a positron beam with an energy of 150 GeV . Following the beam tests, the mini-FoCal was temporarily placed in the ALICE cavern to study its performance under realistic experimental conditions over one month, and preliminary results are presented.