Speaker
Description
In non-central heavy-ion collisions, the initial strong magnetic (B) field can give rise to a broad range of phenomena, such as the splitting of Landau levels under strong B-fields, which has significant implications in QCD [1]. The neutral ($K^{*0}$) and charged ($K^{*\pm}$) vector mesons have similar masses and isospin; however, their quark magnetic moments differ by a factor of five, making them ideal probes for studying Landau level splitting and potential isospin symmetry breaking in the presence of B-fields [2]. The recent observation of isospin violation in neutral and charged kaons by NA61/SHINE challenges the assumption of isospin symmetry in QCD, though the cause remains unknown [3]. A difference in $K^{*0,\pm}$ yields due to B-field can feeddown ($K^{*0} \rightarrow K^{\pm} + \pi^{\mp}$, $K^{*\pm} \rightarrow K_{S}^{0} +\pi^{\pm}$) into the inclusive neutral and charged kaon yields, and contribute to the above apparent isospin violation.
In this talk, we will present the invariant mass peak position and its width, transverse momentum ($p_{T}$) spectra, yields ($dN/dy$), and $\langle p_{T} \rangle$ of $K^{*0,\pm}$ mesons near mid-rapidity, utilizing collisions involving isospin-asymmetric nuclei (Au+Au, Ru+Ru, Zr+Zr) and isospin-symmetric nuclei (O+O), as well as p+p collisions at $\sqrt{s_{NN}} = 200$ GeV. We report on particle ratios, including $K^{*\pm}/K^{*0}$ and $K^{\pm}/K_{S}^{0}$, as a function of $p_{T}$ and centrality in various heavy-ion collision systems. Results from p+p collisions, which are expected to have no B-field effect, serve as a good baseline. Additionally, results from BES-II Au+Au collisions ($\sqrt{s_{NN}} = 7.7 - 19.6$ GeV) will be presented to study the energy dependence of the above ratios. This study offers comprehensive insights into Landau levels, isospin violation, and late-stage B-fields in QCD medium.
[1] F. Bruckmann et. al., Phys. Rev. C 96, 074506 (2017)
[2] K. Xu et. al., Phys. Lett. B 809, 135706 (2020)
[3] H. Adhikary et. al, (NA61/SHINE collaboration), 2312.06572
| Category | Experiment |
|---|---|
| Collaboration (if applicable) | STAR |
