Relativistic Heavy Ion Collisions
High Acceptance Di-Electron Spectrometer
The investigation of hadron properties inside nuclear matter at normal and high densities and temperatures is one of the main goals of current nuclear physics studies. Heavy ion, pion and proton induced reactions on heavy nuclei in a 1-3.5 GeV kinetic beam energy region are the proper tool to probe particle properties in long-living dense state of nuclear matter. The matter created in such collisions differs from the one studied at SPS, RHIC or LHC because it consists mainly of baryons (nucleons and its excited states- baryon resonances) and little mesons and can be compressed up to 3 times nuclear matter density for about 10-12 fm/c. Di-electron pairs originating from in-medium hadron decays and rare strange hadrons (kaons, hyperons) are the main probes measured in the experiment. Since conclusions on in-medium effects rely strongly on the understanding of hadron properties in vacuum and their production mechanism in nucleon-nucleon collisions a complementary program focusing on e+e-, kaon and hyperon (Σ, Λ) production in elementary collisions is also needed.
In order to investigate this phenomenon, the electron-positron pair spectrometer HADES (High Acceptance Di-Electron Spectrometer) was set up, and is in operation at GSI (Helmholtzzentrum für Schwerionenforschung)Darmstadt (Germany) by an international collaboration of 17 institutions from 9 European countries. It is optimized for the detection of leptons exploiting threshold like RICH (Ring Imaging Cherenkov) detector subsystem. In the same time it is very efficient spectrometer of all charged particles like protons, pions, kaons etc. It is using both relativistic heavy ion beams and secondary pion beam provided by SIS18 facility.
The members of our group actively participate in data analysis, paper writing, proposals of new experiments etc. Our main goals are identification of produced particles, reconstruction of mesons decaing into di-lepton and-or pion pairs, flow studies etc.
In addition to that, our group was involved in the construction and is involved in the operation of the two HADES detector subsystems:
- large (~5 meters high) wall consisting from 384 scintillation rods (up to 2,5 meters long) Time-of-flight system (TOF) It ´s purpose is to measure time of flight of charge particles with very high precision of about 100 psec and in combination with other subsystem properly identify them as well as measure their energy.
- smaller Forward Wall (FW hodoscope) consisting from 380 square scintillation detectors covering small polar angles serves for determination of the reaction plane as well as of collision centrality.
Further, sspectrometer HADES is operated since 2018 in the framework of newly build Large Research Infrastructure FAIR(Facility for Antiproton and Ion Research), which is ESFRI landmark (European Strategy Forum on Research Infrastructures) located at GSI. Our group is involved in that context in the corresponding upgrade activities of HADES, particularly in the design and construction of new detector ECAL (Electromagnetic Calorimeter). This is large wall consisting from 978 lead glass modules. The role of ECAL is to identify and determine the energy of neutral particles like pions and eta mesons via their two photon decay. The mass and energy of neutral particle can be computed from energies and directions of photons detected in lead glass modules.
Team members of the HADES experiment:
Andrej Kugler (vedoucí skupiny)
Pablo Ramos Rodrigues
Andrej Kugler, firstname.lastname@example.org
The phase diagram in the region of high baryonic density and rather low temperature is expected to show rich structure, like critical point, phase transition between hadronic and partonic matter, or new phases of matter, i.e. quarkyonic matter. The prove of existence of such structures would be breakthrough in our understanding of strong interaction. Therefore it is a main goal of many research activities in high energy heavy ion physics. This research is linked as well with the verification of models , which attempt to describe the fusion of neutron stars generating gravitational waves observed recently (Nobel prize 2017] as well as to understanding supernova explosions. Experiments HADES and CBM in the Nuclear Matter Physics pillar of newly build Large Research Infrastructure FAIR(Facility for Antiproton and Ion Research) will play unique role in the studies of the equation-of-state of nuclear matter at neutron star core densities. Experiment CBM is designed to measure at very high reaction rates up to 10 MH. This is crucial for to achieve the required precision during multi-differential measurement of rare probes such as multi-strange hyperons, charmed particles and vector mesons, which are sensitive to the dense phase of fireball created during the heavy ion collision. zone. Most of these measurements will be carried out for the first time in the energy domain 1-10 GeV/nucleon available at SIS100 accelerator of FAIR.
Our group is involved in design and construction of hadron calorimeter PSD (Projectile Spectator Detector) and in tests of its prototypes. The PSD will measure main characteristic features of heavy ion collisions like centrality, reaction plane and directed flow. PSD is one of detector subsystem of CBM. It will be placed at distance of about 8 m from the target and will detect projectile spectators, i.e. noninteracting nucleons and fragments emitted forward at low polar angels. The PSD will be located very close to the beam line and therefore high intensity beam will result in very high radiation dose. Our group is exploiting neutron source at NPI cyclotron is carrying out test of radiation hardness of corresponding components and test if they stay operational up to 3×1012 n/cm2. We are testing for example silicon photomultipliers SiPM which will be used to read out light from PSD modules. We are participating also on R&D of other aspects of PSD, simulations of directed flow measurement by PSD, tests of PSD supermodule at CERN, construction of support frame for PSD together with our colleagues from Czech Technical University etc.
Team members of the CBM experiment:
Andrej Kugler, email@example.com