## Abstract

In this letter we report the first multi-differential measurement of correlated pion-proton pairs from 2 billion Au+Au collisions at s_{NN}=2.42 GeV collected with HADES. In this energy regime the population of Δ(1232) resonances plays an important role in the way energy is distributed between intrinsic excitation energy and kinetic energy of the hadrons in the fireball. The triple differential d^{3}N/dM_{π±p}dp_{T}dy distributions of correlated π^{±}p pairs have been determined by subtracting the πp combinatorial background using an iterative method. The invariant-mass distributions in the Δ(1232) mass region show strong deviations from a Breit-Wigner function with vacuum width and mass. The yield of correlated pion-proton pairs exhibits a complex isospin, rapidity and transverse-momentum dependence. In the invariant mass range 1.1<M_{inv}(GeV/c^{2})<1.4, the yield is found to be similar for π^{+}p and π^{−}p pairs, and to follow a power law 〈A_{part}〉^{α}, where 〈A_{part}〉 is the mean number of participating nucleons. The exponent α depends strongly on the pair transverse momentum (p_{T}) while its p_{T}-integrated and charge-averaged value is α=1.5±0.08^{st}±0.2^{sy}.

Original language | English |
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Article number | 136421 |

Journal | Physics Letters B |

Volume | 819 |

DOIs | |

State | Published - 10 Aug 2021 |

## Keywords

- Baryonic resonances
- Freezeout
- Heavy-ion reactions