The Relativistic Heavy Ion Collider (RHIC) accelerates nuclei to ultra-relativistic velocities, producing some of the strongest known magnetic fields in the Universe (1014 − 1015 Tesla). The highly Lorentz-contracted Coulomb fields of the nuclei generate a flux of linearly polarized quasi-real photons that can interact via the Breit-Wheeler process to produce electron-positron pairs (γγ → e+e−). Experimental data presented in this article are consistent with Breit-Wheeler theory across all measured differentials. The detected pairs are produced predominantly at low transverse momentum (P) with a smooth invariant mass distribution, with the individual e± preferentially aligned along the beam direction, and with a 4th-order modulation in azimuth between the e+e− pair and e± momenta. The P spectrum broadens from large to small impact parameters. Our observation opens new opportunities to study Quantum Chromodynamics under extreme conditions and provides a new tool for interdisciplinary study of extreme electromagnetic fields.
|Original language||English (US)|
|State||Published - Oct 27 2019|
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