Project Details
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Exploring the strangeness dimension of the phase diagram of strongly-interacting matter

Subject Area Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
Term from 2019 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 405580046
 
Final Report Year 2023

Final Report Abstract

The investigation of strongly interacting matter under extreme conditions is a very important topic in modern high energy nuclear physics with close ties to astrophysics and cosmology. Various experimental efforts are currently on-going, e.g. the Beam Energy Scan (BES) program of the STAR collaboration at the Relativistic Heavy-Ion Collider (RHIC) in the USA, in order to systematically study the phase diagram of QCD-matter with high energy heavy-ion collisions. Another, dedicated detector system for the investigation of highly compressed baryonic matter is currently being set-up by the CBM collaboration at FAIR (Facility of Antiproton and Ion Research) in Darmstadt, Germany. An indispensable prerequisite for the interpretation of this data is a realistic modelling of the dynamics of heavy-ion collisions. Therefore, the transport model PHQMD (Parton Hadron Quantum Molecular Dynamics) was developed in the context of this project. It was on one side used for comparisons to existing data and on the other side to make predictions for upcoming experimental efforts. PHQMD allows in particular to perform calculations on the production of light nuclei and hypernuclei, whose production mechanisms in the hot and dense environment of heavy-ion collisions were not fully understood. The comparisons of PHQMD predictions with available data, however, resulted in a very good agreement. The very remarkable observation that under these extreme conditions even very lightly bound objects, such as the deuteron or the hypertriton, are produced with relatively high rates and are able to survive the evolution of the fireball was discussed in the community extensively under the headline “ice in fire”-puzzle (or also “snowball in hell”). This problem found a natural solution within the PHQMD approach, as within this model the production of light (hyper-)nuclei mainly happens in the wake of the outwardly expanding wave of super-dense and hot matter. In this region of the collision system the conditions are such that these clusters can be bound via the nucleon potentials and are able to survive the further evolution of the system. In order to assure that the PHQMD model is widely accessible to the community, a lot of effort was invested in integrating the model into the corresponding software frameworks of the experimental collaborations (CBM (FAIR) and NICA (JINR)). It is thus now available for various physics performance studies and used to improve the experimental setups. Furthermore, numerous predictions were performed for comparisons with data of already running experiments (STAR (RHIC), HADES (GSI), NA61 (CERN)) and found their way into many corresponding publications of these collaborations.

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