Compressed Baryonic Matter

The research group led by Ľuboš Krupa is studying strongly interacting matter under extreme conditions, one of the most exciting research programs in modern nuclear physics. The recent discoveries of neutron star mergers and supermassive neutron stars challenge our knowledge on high-density strong-interaction (QCD) matter, like its equation-of-state (EOS) and the microscopic degrees-of-freedom. The mission of the Compressed Baryonic Matter (CBM) experiment is to produce and investigate dense nuclear matter in energetic heavy-ion collisions, to explore the high-density EOS, and to search for new phases of matter, which may feature characteristic structures such as a first-order phase transition with a region of phase coexistence and a critical endpoint.

The scientific goal of the CBM experiment is to find answers to the following fundamental questions:

  • What is the high-density equation-of-state of nuclear matter, which is relevant for our understanding of supernova, the structure of neutron stars, and the dynamics of neutron star mergers?
  • What are the relevant degrees of freedom at high densities? Is there a phase transition from hadronic to quark-gluon matter, a region of phase coexistence, and a critical point? Do exotic QCD phases like quarkyonic matter exist? Can we find experimental evidence for the restoration of chiral symmetry, in order to shed light on the generation of hadron masses?
  • How far can we extend the chart of nuclei towards the third (strange) dimension by producing single and double hypernuclei? Which role do hyperons play in the core of neutron stars?

The Olomouc group is part of the international HADES collaboration, which includes more than 120 members from 13 European countries. We are involved in the operation and maintenance of the detector system and developed in cooperation with the scientific infrastructure departments of GSI different detector systems and components of the data acquisition system.

HADES is a versatile, High Acceptance DiElectron Spectrometer operating with beam extracted from the heavy ion synchrotron SIS18. It uses directed beam from the synchrotron or optionally secondary pion beams produced in a production target 15 m upstream from the HADES target point. It combines a magnetic spectrometer with detector systems specialized in detecting rare decay products such as electrons and positrons from conversion decays of hadrons. The spectrometer features a sophisticated superconducting toroid, low-mass drift chambers, a ring-imaging Cherenkov detector using a CsI photocathode and a pre-shower detector. The time-of-flight system uses diamond start detectors and scintillator and resistive plate based stop detectors. The spectrometer has been running since the beginning of the century and is part of the CBM/HADES project for FAIR.

A deeper understanding of the microscopic properties of baryon-rich QCD matter requires systematic multi-differential analyses of various observables with a large collision systems. The main tasks in this direction of research are:

  1. Properties of the dense hadronic medium in the vicinity of a first-order nuclear liquid-gas phase transition and critical point.
  2. Onset of thermal radiation in baryon rich matter to study the microscopic properties of the fireball.
  3. Measurement of the fireball lifetime and temperature.
  4. Mapping the caloric curve of nuclei.
  5. Understanding the strangeness production and in-medium propagation.
  6. Probing the equation-of-state and nuclear symmetry energy at high densities.

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