Refine
Year of publication
Document Type
- Article (321)
- Preprint (150)
- Working Paper (1)
Language
- English (472)
Has Fulltext
- yes (472)
Is part of the Bibliography
- no (472)
Keywords
- BESIII (14)
- Branching fraction (9)
- LHC (9)
- e +-e − Experiments (9)
- Particle and Resonance Production (6)
- Quarkonium (6)
- Hadronic decays (5)
- ALICE experiment (4)
- Branching fractions (4)
- Lepton colliders (4)
Institute
- Physik (440)
- Frankfurt Institute for Advanced Studies (FIAS) (167)
- Informatik (137)
- Informatik und Mathematik (3)
- Medizin (2)
- ELEMENTS (1)
Streamer chamber data for collisions of Ar + KCl and Ar + BaI2 at 1.2 GeV/nucleon are compared with microscopic model predictions based on the Vlasov-Uehling-Uhlenbeck equation, for various density-dependent nuclear equations of state. Multiplicity distributions and inclusive rapidity and transverse momentum spectra are in good agreement. Rapidity spectra show evidence of being useful in determining whether the model uses the correct cross sections for binary collisions in the nuclear medium, and whether momentum-dependent interactions are correctly incorporated. Sideward flow results do not favor the same nuclear stiffness parameter at all multiplicities.
In the past two decades, pions created in the high density regions of heavy ion collisions have been predicted to be sensitive at high densities to the symmetry energy term in the nuclear equation of state, a property that is key to our understanding of neutron stars. In a new experiment designed to study the symmetry energy, the multiplicities of negatively and positively charged pions have been measured with high accuracy for central 132Sn+124Sn, 112Sn+124Sn, and 108Sn+112Sn collisions at E/A = 270 MeV with the SπRIT Time Projection Chamber. While individual pion multiplicities are measured to 4% accuracy, those of the charged pion multiplicity ratios are measured to 2% accuracy. We compare these data to predictions from seven major transport models. The calculations reproduce qualitatively the dependence of the multiplicities and their ratios on the total neutron and proton number in the colliding systems. However, the predictions of the transport models from different codes differ too much to allow extraction of reliable constraints on the symmetry energy from the data. This finding may explain previous contradictory conclusions on symmetry energy constraints obtained from pion data in Au+Au system. These new results call for still better understanding of the differences among transport codes, and new observables that are more sensitive to the density dependence of the symmetry energy.