First measurement of the spin interference dynamics of the Drell-Söding process in Au+Au 200 GeV collisions

Target Journal: PRL

PA: Daniel Brandenburg, Sam Corey, Xinbai Li, Lijuan Ruan, Zebo Tang, Kaiyang Wang, Xin Wu, Zhangbu Xu, Wangmei Zha

Abstract

In relativistic heavy-ion collisions, the interplay of photoproduction via photon-nuclear interaction creates a rich environment to explore quantum interference at an unprecedented femtometer scale. For exclusive \( \pi^+ \pi^- \) production, the resonance and continuum production \( \pi^+ \pi^- \) originate from distinct production mechanisms. The continuum \( \pi^+ \pi^- \), mainly produced by the Drell-Söding process, involves a virtual \( \pi^+/\pi^- \) diffraction-scattered on the nucleus. The fluctuation of short-lived \( \pi^+ \pi^- \) pairs is ephemeral, lasting within the time-scale for strong interaction, which could indicate the transient nature of quantum entanglement.

In this paper, we present the first measurement of the diffractive \( p_T \) spectrum and the entanglement-enabled spin interference (EESI) through \( A_{2 \Delta \phi} \) for the Drell-Söding process. We observe distinct interference dynamics between \( \rho^0 \) photoproduction and the Drell-Söding process, providing a unique opportunity to explore the effect of the production mechanism on EESI. Additionally, we observe \( A_{2 \Delta \phi} \) with no clear dependence on mass for \( p_T < 0.1 \) GeV/c and a notably stronger \( A_{2 \Delta \phi} \) for the Drell-Söding process.

Summary & Conclusions

• We present the first measurement of diffractive \( p_T \) spectrum and spin interference measurement for Drell-Söding process.
• The first time to measure \( A_{2 \Delta \phi} \) on mass dependence for \( \rho^0 \) photoproduction and Drell-Söding process. The results shows no clear dependence and an obviously stronger \( A_{2 \Delta \phi} \) for Drell-Söding process.
• The measurement of Drell-Söding process with no intermediate state implicate that the quantum effect (entanglement) could happen around the time scale for strong interaction (no entanglement purity evolution on mass).
• From comparison of \( \rho^0 \) photoproduction and Drell-Söding process, results show a notable production mechanism impact and indicate the photon parton distribution.
• Important to EIC \( \phi \) and direct \( K^+ K^- \); Baseline for mc and model (current no channel).