R&D Of Electromagnetic Calorimeter For NICA/MPD

Investigation of hot and dense baryonic matter is a challenging task in modern physics.It provides information on the in-medium properties of hadrons and nuclear matter equation of state,allows a search for possible manifestations of the deconfinement and/or chiral symmetry restoration,phase transition,mixed phase and critical end point,and sheds light on the evolution of the Early Universe and formation of neutron stars.An essential part of the JINR scientific program resulted from many discussions in view of the Dubna Nuclotron upgrade is dedicated to the study of hot and dense baryonic matter.Realization of this ambitious goal is related to the construction of a new JINR accelerator complex the Nuclotron-based Ion Collider fAcility(NICA)to provide collisions of heavy-ions over a wide range of atomic masses,from Au+Au collisions at a centre-of-mass energy of(?)=4-11GeV(for Au79+)and an average luminosity of L≈1027 cm-2s-1,to proton-proton collisions with(?)=4-20GeV and L≈1030cm-2s-1.Two interaction points are foreseen at the NICA collider,which provide a possibility for two detectors to operate simultaneously.One of these detectors,the MultiPurpose Detector(MPD),is optimized for the study of properties of hot and dense matter in heavy-ion collisions.The detector to explore phase diagram of strongly interacting matter in a high track multiplicity environment has to cover a large phase space,be functional at high interaction rates and comprise high efficiency and excellent particle identification capabilities.It must also be based on the recent detector developments in order to meet the ambitious physics requirements,and to be of comparatively reasonable costElectromagnetic 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 selectedThe entire ECal is a barrel structure consisting of 43008 ECal towers 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 ECalThis topic starts from three aspects of simulation,key technology research and prototype test,and realizes a more complete study of MPD-ECal.The detector was simulated by using GEANT 4 and MpdRoot simulation software.The specific conclusions are as follows.The size of the ECal module is determined by simulation,and the physical properties that the detector can achieve are optimal at the selected size.The simulation obtained the linearity of the detector energy and verified that the detector has a good linear response.In view of the fact that MPD-ECal is involved in particle identification,the difference in deposition energy of the inhomogeneous particles in the ECal module is simulated,and the feasibility of the detector module for particle identification is verified.The position resolution of the detector in the case of a 3×3 module array is simulated After the auxiliary correction,the position resolution of the detector at 3 GeV energy can reach 3 mm.The overall energy deposition of the MPD-ECal was measured and the simulation concluded that the energy deposition is a single-valued function related to the incident particle energy,independent of the particle pseudo-rapidity.Through the simulation data analysis,the π0 reconstruction method is mastered,and the π0 reconstruction energy spectrum is obtainedSecond,the key technology research on MPD-ECal was carried out The specific research results are as follows.The scintillator luminescence properties were studied,the photoelectron number measurement method was mastered,and a plastic scintillator excellent in luminescence performance was selected.The luminescent and mechanical properties of wavelength shifting fibers were investigated.It is concluded that BCF91A and Y11 are consistent in luminescence performance,but Y11 is more stable in bending resistance and BCF91A is less resistant to bending.The reflective properties of various reflective materials used in MPD-ECal were studied,and many excellent materials were selected,which has a strong guiding effect on subsequent detector optimization.Mastered the key technologies in the prototype manufacturing process,such as dimensional accuracy control,pressurization method,wedge-type module cutting method,etc.,and studied the influence of temperature change on the mechanical stability of ECal module.The mastery of these key technologies has accumulated invaluable experience in the production of shashlik calorimeters.Up to now,the production of one ECal module prototype and two ECal unit prototypes has been successfully completed.Provided conditions for prototype testing Third,the prototype completed the cosmic ray test and beam test,the test results are as follows.The ECal tower prototype was tested.By comparing the SoLID-ECal cosmic ray test results,the energy resolution of ECal tower has reached 5%/(?).Go to DESY to finish the beam test for two ECal unit prototypes.A well-fit energy linear relationship between NPE and electron energy,energy resolution around 4.5%,time resolution around 212.4ps and position resolution around 4.7mm at 1.6GeV were achieved.All these results show that the prototype of ECal is 21 fully capable of the requirement of the NICA/MPD.There is still a lot of work worthy of further research,including calibration of detectors,running of collision experiments,analysis of experimental results,physical discussion,and so on.