2019/10/31 by STAR Collaboration, M. S. Abdallah, B. E. Aboona +402 · 3 citations
Physics and Astronomy · #Atomic physics #High-Energy Particle Collisions Research #Meson #Nuclear physics #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum Chromodynamics and Particle Interactions #Quantum chromodynamics #nucl-ex
paper · pdf · doi:10.1103/physrevlett.127.052302
published as Phys. Rev. Lett. 127, 052302 (2021) · Keywords: Ultra-peripheral collisions, Breit-Wheeler process, vacuum birefringence, two-photon process, QED under extreme conditions, strong fields
openalex publication_date 2021/07/27 · openalex created_date 2021/08/02 · arxiv created 2021/08/04 · arxiv updated 2021/08/05 · openalex updated_date 2026/08/06
The Breit-Wheeler process which produces matter and antimatter from photon collisions is experimentally investigated through the observation of 6085 exclusive electron-positron pairs in ultraperipheral Au+Au collisions at √sNN=200 GeV. The measurements reveal a large fourth-order angular modulation of cos4\mathrm\ensuremathΔ\ensuremathφ=(16.8\ifmmode±\else\textpm\fi2.5)% and smooth invariant mass distribution absent of vector mesons (\ensuremathφ, \ensuremathω, and \ensuremathρ) at the experimental limit of \ensuremath≤0.2% of the observed yields. The differential cross section as a function of e+e^\ensuremath- pair transverse momentum P_\ensuremath⊥ peaks at low value with √⟨P_\ensuremath⊥2⟩=38.1\ifmmode±\else\textpm\fi0.9 MeV and displays a significant centrality dependence. These features are consistent with QED calculations for the collision of linearly polarized photons quantized from the extremely strong electromagnetic fields generated by the highly charged Au nuclei at ultrarelativistic speed. The experimental results have implications for vacuum birefringence and for mapping the magnetic field which is important for emergent QCD phenomena.