5 Search Results

Meson-baryon systems with strangeness content provide a unique laboratory for investigating the strong interaction and testing theoretical models of hadron structure and dynamics. In this work, the measured correlation functions for oppositely charged $$Ξ$$-K and $$Ξ$$ − 𝜋 pairs obtained in high-multiplicity pp collisions at $$\sqrt{𝑠}$$ = 13 TeV at the LHC are presented. For the first time, high-precision data on the $$Ξ$$-K interaction are delivered at small relative momenta. The scattering lengths, extracted via the Lednický–Lyuboshits expression of the pair wavefunction, indicate a repulsive and a shallow attractive strong interaction for the $$Ξ$$-K and $$Ξ$$ − 𝜋 systems, respectively.more » The $$Ξ$$(1620) and $$Ξ$$(1690) states are observed in the $$Ξ$$ − 𝜋 correlation function and their properties, mass and width, are determined. These measurements are in agreement with other available results. Such high-precision data can help refine the understanding of these resonant states, provide stronger constraints for chirally motivated potentials, and address the key challenge of describing the coupled-channel dynamics that may give rise to molecular configurations .« less

Here, this paper reports measurements of the transverse energy per unit pseudorapidity (𝑑⁢𝐸_𝑇/𝑑⁢𝜂) produced in Au + Au collisions at $$\sqrt{𝑠_{𝑁⁢𝑁}}$$ = 200 GeV, performed with the sPHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The results cover the pseudorapidity range |𝜂| < 1.1 and constitute the first such measurement performed using a hadronic calorimeter at RHIC. Measurements of 𝑑⁢𝐸_𝑇/𝑑⁢𝜂 are presented for a range of centrality intervals and the average 𝑑⁢𝐸_𝑇/𝑑⁢𝜂 as a function of the number of participating nucleons, 𝑁_part, is compared to a variety of Monte Carlo heavy-ion event generators. The results are in agreement withmore » previous measurements at RHIC, and feature an improved granularity in 𝜂 and improved precision in low-𝑁_part events.« less

The pseudorapidity distribution of charged hadrons produced in Au + Au collisions at a center-of-mass energy of $$\sqrt{s_{NN}}$$ = 200 GeV is measured using data collected by the sPHENIX detector. Charged hadron yields are extracted by counting cluster pairs in the inner and outer layers of the Intermediate Silicon Tracker, with corrections applied for detector acceptance, reconstruction efficiency, combinatorial pairs, and contributions from secondary decays. The measured distributions cover |η| < 1.1 across various centralities, and the average pseudorapidity density of charged hadrons at mid-rapidity is compared to predictions from Monte Carlo heavy-ion event generators. This result, featuring full azimuthalmore » coverage at mid-rapidity, is consistent with previous experimental measurements at the Relativistic Heavy Ion Collider, thereby supporting the broader sPHENIX physics program.« less

We report on new measurements of elliptic flow (v₂) of electrons from heavy-flavor hadron decays at mid-rapidity (|y| < 0.8) in Au+Au collisions at $$\sqrt{s{NN}}$$ = 27 and 54.4 GeV from the STAR experiment. Heavy-flavor decay electrons (eHF) in Au+Au collisions at $$\sqrt{s{NN}}$$ = 54.4 GeV exhibit a non-zero v₂ in the transverse momentum (p_T) region of p_T < 2 GeV/c with the magnitude comparable to that at $$\sqrt{s{NN}}$$=200 GeV. The measured e^HF v₂ at 54.4 GeV is also consistent with the expectation of their parent charm hadron v₂ following number-of-constituent-quark scaling as other light and strange flavor hadrons atmore » this energy. These suggest that charm quarks gain significant collectivity through the evolution of the QCD medium and may reach local thermal equilibrium in Au+Au collisions at $$\sqrt{s{NN}}$$=54.4 GeV. The measured e^HF v₂ in Au+Au collisions at $$\sqrt{s{NN}}$$ = 27 GeV is consistent with zero within large uncertainties. The energy dependence of v₂ for different flavor particles (π,Φ,D⁰/e^HF) shows an indication of quark mass hierarchy in reaching thermalization in high-energy nuclear collisions.« less