Exploring millicharged particles (particles with small rational or irrational charges) has become a central focus in contemporary particle physics and cosmology. Linked to charge quantization, which spurred Dirac Quantization and Grand Unification Theories, the millicharge searches are also testing grounds for string theory and quantum gravity.
I will give a general introduction to millicharged particles and present a novel approach to leverage them for probing reheating cosmology—a pivotal phase post-inflation, shaping the current Universe's particle composition. Millicharge searches offer insights into reheating scenarios and temperatures. I will also discuss the irreducible cosmic millicharged background and implications on the dark matter observations, the 21-cm absorption spectrums, Big Bang nucleosynthesis, and CMB measurements.
Finally, the talk delves into dedicated experimental efforts, notably the FORMOSA experiment at CERN, LANSCE-mQ at LANL, and neutrino experiments at Fermilab, which may help unveil the mysteries in cosmology and fundamental theories.
