Speaker
Description
The nature of the high invariant mass region ($M_{K^{+}K^{-}} > 1.1~\mathrm{GeV}/c^{2}$) in coherent $K^{+}K^{-}$ photoproduction in ultra-peripheral heavy-ion collisions (UPCs) has remained an unresolved question in physics. Previous ALICE measurements have shown non-trivial structures in this region, but the underlying production mechanisms are still under debate. The relative contributions from photon–nucleus ($\gamma A$) processes - including coherent $\phi$-meson decay and non resonant Drell--Soding interference - and from the diphoton fusion($\gamma\gamma$) are not yet unambiguously determined.
To shed light on these open issues, we present a new measurement of coherent $K^{+}K^{-}$ photoproduction in Au+Au ultra-peripheral collisions at $\sqrt{s_{_{\mathrm{NN}}}} = 200~\mathrm{GeV}$ with the STAR detector at RHIC. The $K^{+}K^{-}$ pairs are identified using the TPC and TOF detectors, and a clear coherent signal is observed at ( $p_T^{K^{+}K^{-}} < 0.2~\mathrm{GeV}/c$) and ( $M_{K^{+}K^{-}} > 1.1~\mathrm{GeV}/c^{2}$). The invariant mass distribution and differential cross sections are studied to explore the relative roles of resonant, non-resonant, and two-photon processes. This measurement provides new constraints on strangeness photoproduction and on the dynamics of photon--nucleus and two-photon processes in heavy-ion UPCs.
| Is this an experimental talk? | Yes |
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| Is this on behalf of a collaboration? | Yes |
| Which collaboration? | STAR |
| Are you willing to present as a poster if it is not selected for oral presentation? | Yes |