Speaker
Description
Neutral and charged vector mesons can be sensitive to isospin-violating effects induced by Landau level splitting in the presence of a strong
magnetic field ($B$) within a QCD medium~\cite{meson_spiltting_njl}. One such example is the neutral $K^{*0}$ ($d\bar{s}$) and the charged $K^{*+}$ ($u\bar{s}$), which have similar masses and isospin. However, the magnetic moments of their constituent quarks differ significantly, by approximately a factor of five. 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~\cite{na61_isospin}. 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 discuss 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 will provide comprehensive understanding of Landau levels, isospin violation, and late-stage B-fields in QCD medium.
