New forward hadron calorimeter and hodoscope for the BM@N heavy ions experiment

New forward hadron calorimeter with transverse and longitudinal segmentation has been developed and constructed for the upgraded fixed target BM@N experiment at JINR, Dubna. The main purpose of this calorimeter is to provide event-by-event centrality and reaction plane orientation measurements in nucleus-nucleus collisions. The design of the hadron calorimeter composed of sampling lead/scintillator modules with a beam hole in the center is discussed. The light collection from longitudinal sections in modules is provided by Wave Length Shifting (WLS) fibers embedded in scintillator plates. Micro-pixel photodetectors (Hamamatsu MPPCs) are used for light detection from each longitudinal section of modules. The measured light yield is about 50 photoelectrons per section for MIPs. Sampling ADCs are used for signal readout in the calorimeter. The performance of the FHCAL is discussed. For centrality measurement additional forward quartz hodoscope is developed to measure charge of fragments in the FHCAL beam hole. The method of collision centrality determination is discussed.