beecee Posted July 29, 2021 Posted July 29, 2021 https://phys.org/news/2021-07-collisions-matterantimatter-pure-energy.html Collisions of light produce matter/antimatter from pure energy: Scientists studying particle collisions at the Relativistic Heavy Ion Collider (RHIC)—a U.S. Department of Energy Office of Science user facility for nuclear physics research at DOE's Brookhaven National Laboratory—have produced definitive evidence for two physics phenomena predicted more than 80 years ago. The results were derived from a detailed analysis of more than 6,000 pairs of electrons and positrons produced in glancing particle collisions at RHIC and are published in Physical Review Letters. The primary finding is that pairs of electrons and positrons—particles of matter and antimatter—can be created directly by colliding very energetic photons, which are quantum "packets" of light. This conversion of energetic light into matter is a direct consequence of Einstein's famous E=mc2 equation, which states that energy and matter (or mass) are interchangeable. Nuclear reactions in the sun and at nuclear power plants regularly convert matter into energy. Now scientists have converted light energy directly into matter in a single step. The second result shows that the path of light traveling through a magnetic field in a vacuum bends differently depending on how that light is polarized. Such polarization-dependent deflection (known as birefringence) occurs when light travels through certain materials. (This effect is similar to the way wavelength-dependent deflection splits white light into rainbows.) But this is the first demonstration of polarization-dependent light-bending in a vacuum. more at link.............. the paper: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.052302 Measurement of e+e− Momentum and Angular Distributions from Linearly Polarized Photon Collisions ABSTRACT: 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 cos4Δϕ=(16.8±2.5)% and smooth invariant mass distribution absent of vector mesons (ϕ, ω, and ρ) at the experimental limit of ≤0.2% of the observed yields. The differential cross section as a function of e+e− pair transverse momentum P⊥ peaks at low value with √〈P2⊥〉=38.1±0.9 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.
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