In-medium $\Delta (1232)$ potential, pion production in heavy-ion collisions and the symmetry energy

Abstract

Using the dcQMD transport model, the isoscalar and isovector in-medium potentials of the $\Delta$(1232) baryon are studied and information regarding their effective strength is obtained from a comparison to experimental pion production data in heavy-ion collisions below 800 MeV/nucleon impact energy. The best description is achieved for an isoscalar potential moderately more attractive than the nucleon optical potential and a rather small isoscalar relative effective mass m${}_{\Delta }^{\ast }\approx$ 0.45. For the isovector component only a constraint between the potential's strength at saturation and the isovector effective mass difference can be extracted, which depends on quantities such as the slope of the symmetry energy and the neutron-proton effective mass difference. These results are incompatible with the usual assumption, in transport models, that the $\Delta$(1232) and nucleon potentials are equal. The density dependence of symmetry energy can be studied using the high transverse momentum tail of pion multiplicity ratio spectra. Results are however correlated with the value of neutron-proton effective mass difference. This region of spectra is shown to be affected by uncertain model ingredients such as the pion potential or in-medium correction to inelastic scattering cross-sections at levels smaller than 10$\%$. Extraction of precise constraints for the density dependence of symmetry energy above saturation will require experimental data for pion production in heavy-ion collisions below 800 MeV/nucleon impact energy and experimental values for the high transverse momentum tail of pion multiplicity ratio spectra accurate to better than 5$\%$.

22 pages, 13 figures

References in corpus (16)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Neutron Star Observations: Prognosis for Equation of State Constraints
• Results of the ASY-EOS experiment at GSI: The symmetry energy at suprasaturation density
• The Giant Dipole Resonance as a quantitative constraint on the symmetry energy
• Symmetry energy from elliptic flow in 197Au + 197Au
• Systematics of central heavy ion collisions in the 1A GeV regime
• Neutron matter from chiral two- and three-nucleon calculations up to N${}^3$LO
• Isospin effects on sub-threshold kaon production at intermediate energies
• Implications from GW170817 for $\Delta$-isobar admixed hypernuclear compact stars
• Neutron-proton effective mass splitting in neutron-rich matter at normal density from analyzing nucleon-nucleus scattering data within an isospin dependent optical model
• $\Delta$ (1232) effects in density-dependent relativistic Hartree-Fock theory and neutron stars
• Thermal properties of asymmetric nuclear matter with an improved isospin- and momentum-dependent interaction
• Constraining the high-density nuclear symmetry energy with the transverse-momentum dependent elliptic flow
• The neutron/proton ratio of squeezed-out nucleons and the high density behavior of the nuclear symmetry energy
• Effects of energy conservation on equilibrium properties of hot asymmetric nuclear matter
• Decomposition of sensitivity of the symmetry energy observables

Cited by in corpus (2)

• Baryonic dense matter in view of gravitational-wave observations
• Hyperonization in compact stars