2006/07/11 by Holger Gies, Joerg Jaeckel, Andreas Ringwald · 152 citations
Physics and Astronomy · #Atomic and Subatomic Physics Research #Dark Matter and Cosmic Phenomena #Fermion #Magnetic field #Pair production #Particle physics #Photon #Physics #Polarization (electrochemistry) #Production (economics) #Quantum Mechanics and Applications #Quantum mechanics #Standard Model (mathematical formulation) #hep-ex #hep-ph
paper · pdf · doi:10.1103/physrevlett.97.140402
published in Physical Review Letters 97(14), 140402 (American Physical Society) · 4 pages, 2 figures
arxiv created 2006/07/11 · openalex publication_date 2006/10/02 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Possible extensions of the standard model of particle physics suggest the existence of particles with small, unquantized electric charge. Photon-initiated pair production of millicharged fermions in a magnetic field would manifest itself as a vacuum magnetic (VM) dichroism. We show that laser polarization experiments searching for this effect yield, in the mass range below 0.1 eV, much stronger constraints on millicharged fermions than previous laboratory searches. VM birefringence due to virtual pair production gives a slightly better constraint for masses between 0.1 and a few eV. We comment on the possibility that the VM dichroism observed by PVLAS arises from pair production of such millicharged fermions rather than from single production of axionlike particles. Such a scenario can be confirmed or firmly excluded by a search for invisible decays of orthopositronium with a branching-fraction sensitivity of about 10(-9).