Passage of millicharged particles in the electron beam-dump: Refining constraints from SLACmQ and estimating sensitivity of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>NA</mml:mi><mml:mn>64</mml:mn><mml:mi>e</mml:mi></mml:mrow></mml:math>
Nataliya Arefyeva, S. Gninenko, Dmitry Gorbunov, D. Kirpichnikov
Abstract
Millicharged particles (MCPs) arise in many well-motivated extensions of the Standard Model and are a popular subject for experimental searches. We investigate the attenuation of the MCP flux produced at accelerator experiments due to their interactions in the media and demonstrate that it can significantly affect the final sensitivity to the MCP parameter space, leaving its essential part still unexplored. Applying our analysis to the SLACmQ experiment [A. A. Prinz et al., Phys. Rev. Lett. 81, 1175 (1998)], we correct their published exclusion bounds; the obtained results are numerically in a good accordance with A. A. Prinz [Report No. SLAC-R-569]. We also show that this newly reopened area with the MCP masses in the range ${10}^{\ensuremath{-}4}\text{ }\text{ }\mathrm{eV}--1\text{ }\text{ }\mathrm{GeV}$ and charges $\ensuremath{\gtrsim}{10}^{\ensuremath{-}5}e$ can be effectively probed by the $\mathrm{NA}64e$ experiment at the CERN SPS. Light MCPs are mostly produced by a virtual photon in electron scattering off nuclei. The main source of heavy MCP is decays of vector mesons, produced by the electrons on nuclei.