Development of shashlik electromagnetic calorimeter for the NICA/MPD

Abstract

The main goal of the NICA heavy-ion program at JINR is an experimental investigation into the properties of nuclear matter within the energy region of the maximum baryonic density. The Multi Purpose Detector (MPD) is one of the detectors at NICA collider, which is optimized for the study on properties of hot and dense matter in heavy-ion collisions and, in particular, the search for a manifestation of possible deconfinement and/or chiral symmetry restoration phase transitions, critical end-point and mixed quark-hadron phase. Electromagnetic calorimeter (ECal) is an important part of MPD . The particular goal of MPD-ECal is to measure position and energy of photons and electrons. Taking all factors (high energy resolution, high segmentation, large enough distance to the vertex, small Moliere radius, high magnetic field and high time resolution) into consideration, a shashlik-type electromagnetic calorimeter is selected. Therefore the tower consists of 220 layers of lead plates and scintillator plates whose thicknesses are namely 0.3mm/1.5mm. The tower cell is 4×4 cm2 in size. To reduce the dead zones effect, all towers should be cut from four sides at small angles, which will significantly improve the position resolution and the performance homogeneity of the ECal. Currently, energy deposition, energy resolution and position reconstruction are studied through Monte Carlo simulations. A prototype of shashlik Ecal has been built and the cosmic test results show that the number of photoelectrons (Npe) is around 522. By comparing with the previous ECal experimental results and simulation results, it is indirectly considered that the energy resolution of the prototype has reached 5%/√E (GeV) . Key technologies to increase light yield are being studied and will be used in the development of new prototypes.