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HADES experimental overview

Hanna Zbroszczyk

TL;DR

HADES investigates high-density, baryon-rich matter created in low-energy heavy-ion collisions, focusing on hadronic observables, strangeness, and electromagnetic probes. By combining fluctuations, flow, correlations, hypernuclei measurements, and dielectron spectroscopy, the study maps the dense QCD regime and constrains the equation of state. Key findings include the necessity of attractive proton–proton interactions to describe fluctuation data, bell-shaped rapidity distributions for light hypernuclei, and a thermal dielectron component that informs the medium temperature and lifetime. These results refine our understanding of dense QCD matter and lay groundwork for energy-scan programs and CBM collaboration.

Abstract

We report the recent results from the HADES experiment obtained in Au+Au and Ag+Ag collisions at center-of-mass energies per nucleon pair of 2.42 and 2.55 GeV, respectively. In particular, measurements of hadronic and dilepton observables are presented, and prospects for the future experimental program are outlined.

HADES experimental overview

TL;DR

HADES investigates high-density, baryon-rich matter created in low-energy heavy-ion collisions, focusing on hadronic observables, strangeness, and electromagnetic probes. By combining fluctuations, flow, correlations, hypernuclei measurements, and dielectron spectroscopy, the study maps the dense QCD regime and constrains the equation of state. Key findings include the necessity of attractive proton–proton interactions to describe fluctuation data, bell-shaped rapidity distributions for light hypernuclei, and a thermal dielectron component that informs the medium temperature and lifetime. These results refine our understanding of dense QCD matter and lay groundwork for energy-scan programs and CBM collaboration.

Abstract

We report the recent results from the HADES experiment obtained in Au+Au and Ag+Ag collisions at center-of-mass energies per nucleon pair of 2.42 and 2.55 GeV, respectively. In particular, measurements of hadronic and dilepton observables are presented, and prospects for the future experimental program are outlined.
Paper Structure (9 sections, 5 figures)

This paper contains 9 sections, 5 figures.

Table of Contents

  1. Introduction
  2. Physics goals and detector
  3. Hadronic Observables
  4. Fluctuations
  5. Flow
  6. Correlations
  7. Hypernuclei
  8. Dileptons
  9. Summary and outlook

Figures (5)

  • Figure 1: Stretched schematic view of the HADES detector with the setup used in heavy-ion collisions focused on the beam-axis direction.
  • Figure 2: The energy dependence of the normalized proton number factorial cumulants $C_{2}(p)/C_{1}(p)$. The purple box represents the preliminary HADES measurement (scaled down by a factor of 10). The model simulations including only global baryon number conservation are shown as solid green squares, while the open green (open blue) boxes correspond to simulations with attractive (repulsive) proton–proton interactions. The open purple box denotes the result of model simulations incorporating three-particle attractions among protons. The latter provides the best description of the HADES data. For details, see fl4marvin.
  • Figure 3: Left: scaling of elliptic flow as a function of transverse momentum for protons, tritons and helium-3; right: d-$\Lambda$ femtoscopic correlation function for Ag+Ag collisions together with Lednicky-Lyuboshits fit.
  • Figure 4: Left: preliminary normalized rapidity distributions of deuterons, $\Lambda$ hyperons and hypertritons; right: same but for tritons, $\Lambda$ hyperons and hyperhydrogen-4.
  • Figure 5: Left: Invariant mass of dielectron thermal excess pairs; right: mass invariant distribution of elliptic flow for dilepton pairs after subtracting contributions originating from $\pi^0$ decays.