Cosmic millicharge background and reheating probes

Abstract We demonstrate that the searches for dark sector particles can provide probes of reheating scenarios, focusing on the cosmic millicharge background produced in the early universe. We discuss two types of millicharge particles (mCPs): either with, or without, an accompanying dark photon. The...

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Main Authors: Xucheng Gan, Yu-Dai Tsai
Format: Article
Language:English
Published: SpringerOpen 2025-07-01
Series:Journal of High Energy Physics
Subjects:
Online Access:https://doi.org/10.1007/JHEP07(2025)094
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author Xucheng Gan
Yu-Dai Tsai
author_facet Xucheng Gan
Yu-Dai Tsai
author_sort Xucheng Gan
collection DOAJ
description Abstract We demonstrate that the searches for dark sector particles can provide probes of reheating scenarios, focusing on the cosmic millicharge background produced in the early universe. We discuss two types of millicharge particles (mCPs): either with, or without, an accompanying dark photon. These two types of mCPs have distinct theoretical motivations and cosmological signatures. We discuss constraints from the overproduction and mCP-baryon interactions of the mCP without an accompanying dark photon, with different reheating temperatures. We also consider the ∆N eff constraints on the mCPs from kinetic mixing, varying the reheating temperature. The regions of interest in which the accelerator and other experiments can probe the reheating scenarios are identified in this paper for both scenarios. These probes can potentially allow us to set an upper bound on the reheating temperature down to ~ 10 MeV, much lower than the previously considered upper bound from inflationary cosmology at around ~ 1016 GeV. In addition, we derive a new “distinguishability condition”, in which the two mCP scenarios may be differentiated by combining cosmological and theoretical considerations. Finally, we discuss the implications of dedicated mCP searches, future CMB-S4 observations, and the target for experiments when considering the minimally allowed reheating temperature.
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spelling doaj-art-876a8af63c344bdb87c2b0e9e338efb62025-08-20T03:04:12ZengSpringerOpenJournal of High Energy Physics1029-84792025-07-012025712710.1007/JHEP07(2025)094Cosmic millicharge background and reheating probesXucheng Gan0Yu-Dai Tsai1Center for Cosmology and Particle Physics, Department of Physics, New York UniversityLos Alamos National Laboratory (LANL)Abstract We demonstrate that the searches for dark sector particles can provide probes of reheating scenarios, focusing on the cosmic millicharge background produced in the early universe. We discuss two types of millicharge particles (mCPs): either with, or without, an accompanying dark photon. These two types of mCPs have distinct theoretical motivations and cosmological signatures. We discuss constraints from the overproduction and mCP-baryon interactions of the mCP without an accompanying dark photon, with different reheating temperatures. We also consider the ∆N eff constraints on the mCPs from kinetic mixing, varying the reheating temperature. The regions of interest in which the accelerator and other experiments can probe the reheating scenarios are identified in this paper for both scenarios. These probes can potentially allow us to set an upper bound on the reheating temperature down to ~ 10 MeV, much lower than the previously considered upper bound from inflationary cosmology at around ~ 1016 GeV. In addition, we derive a new “distinguishability condition”, in which the two mCP scenarios may be differentiated by combining cosmological and theoretical considerations. Finally, we discuss the implications of dedicated mCP searches, future CMB-S4 observations, and the target for experiments when considering the minimally allowed reheating temperature.https://doi.org/10.1007/JHEP07(2025)094Cosmology of Theories BSMModels for Dark Matter
spellingShingle Xucheng Gan
Yu-Dai Tsai
Cosmic millicharge background and reheating probes
Journal of High Energy Physics
Cosmology of Theories BSM
Models for Dark Matter
title Cosmic millicharge background and reheating probes
title_full Cosmic millicharge background and reheating probes
title_fullStr Cosmic millicharge background and reheating probes
title_full_unstemmed Cosmic millicharge background and reheating probes
title_short Cosmic millicharge background and reheating probes
title_sort cosmic millicharge background and reheating probes
topic Cosmology of Theories BSM
Models for Dark Matter
url https://doi.org/10.1007/JHEP07(2025)094
work_keys_str_mv AT xuchenggan cosmicmillichargebackgroundandreheatingprobes
AT yudaitsai cosmicmillichargebackgroundandreheatingprobes