We study the possibility that dark radiation, sourced through the decay of dark matter in the late Universe, carries electromagnetic interactions. The relativistic flux of particles induces recoil signals in direct detection and neutrino experiments through its interaction with millicharge, electric/magnetic dipole moments, or anapole moment/charge radius. Taking the DM lifetime as 35 times the age of the Universe, as currently cosmologically allowed, we show that direct detection (neutrino) experiments have complementary sensitivity down to $ε\sim 10^{-11}$ $(10^{-12})$, $d_χ/μ_χ\sim 10^{-9}\,μ_B$ $(10^{-13}μ_B)$, and $a_χ/b_χ\sim 10^{-2}\,{\rm GeV}^{-2}$ $(10^{-8}\,{\rm GeV}^{-2})$ on the respective couplings. Finally, we show that such dark radiation can lead to a satisfactory explanation of the recently observed XENON1T excess in the electron recoil signal without being in conflict with other bounds.
We study linear and nonlinear optical properties of electromagnetically induced transparency (EIT) medium interacting with two quantized laser fields for adiabatic EIT case. We show that EIT medium exhibits normal dispersion. Kerr and higher order nonlinear refractive-index coefficients are also calculated in a completely analytical form. It is indicated that EIT medium exhibits giant resonantly enhanced nonlinearities. We discuss the response of the EIT medium to nonclassical light fields and find that the polarization vanishes when the probe laser is initially in a nonclassical state of no s…
While the behavior of the dominant component of the dark matter is reasonably well established by cosmological observables, its particle nature and interactions with the rest of the matter are not known. We consider three dark matter models that admit electromagnetic interaction between baryons and dark matter: (a) milli-charged particle (CCDM) of charge $q_{\rm ccdm}$ and mass $m_{\rm ccdm}$, (b) a neutral atom of two charged particles of mass $m_{\rm dd}$ (DD), and (c) a neutral atom of doubly charged particle and helium nucleus (HeD). We derive and discuss in detail the formation, stability…
We reinterpret the results of the direct searches for dark matter in terms of milli-interacting dark particles. The model reproduces the positive results from DAMA/LIBRA and CoGeNT and is consistent with the absence of signal in the XENON100, CDMS-II/Ge and LUX detectors. Dark atoms, interacting with standard atoms through a kinetic mixing between photons and dark photons and a mass mixing of σ mesons with dark scalars, diffuse elastically in terrestrial matter where they deposit all their energy. Reaching underground detectors through gravity at thermal energies, they form bound states with n…
Dark matter annihilation might power the first luminous stars in the Universe. These types of stars, known as dark stars, could form in $(10^6\mathrm{-}10^8)\,M_\odot$ protohalos at redshifts $z \sim 20$, and they could be much more luminous and larger in size than ordinary stars powered by nuclear fusion. We investigate the formation of dark stars in the self-interacting dark matter (SIDM) scenario. We present a concrete particle physics model of SIDM that can simultaneously give rise to the observed dark matter density, satisfy constraints from astrophysical and terrestrial searches, and add…
Impostor Among $ν$s: Dark Radiation Masquerading as Self-Interacting Neutrinos
Saha Institute of Nuclear Physics（萨哈核物理研究所）；Homi Bhabha National Institute（霍米·巴巴国立学院）；Washington University（华盛顿大学）；Johannes Gutenberg-Universität Mainz（美因茨约翰内斯古腾堡大学）；Southern University of Science and Technology（南方科技大学）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）
The nature of neutrinos, whether Dirac or Majorana, is hitherto not known. Assuming that the neutrinos are Dirac, which needs $B-L$ to be an exact symmetry, we make an attempt to explain the observed proportionality between the relic densities of dark matter (DM) and baryonic matter in the present Universe ${\it i.e.,}\,\, Ω_{\rm DM} \approx 5\, Ω_{\rm B}$. Assuming the existence of heavy $SU(2)_L$ scalar doublet $(X= (X^0, X^-)^T)$ in the early Universe, an equal and opposite $B-L$ asymmetry can be generated in left and right-handed sectors by the CP-violating out-of-equilibrium decay $X^0 \t…
We consider direct-detection searches for sub-GeV dark matter via electron scatterings in the presence of large interactions between dark and ordinary matter. Scatterings both on electrons and nuclei in the Earth's crust, atmosphere, and shielding material attenuate the expected local dark matter flux at a terrestrial detector, so that such experiments lose sensitivity to dark matter above some critical cross section. We study various models, including dark matter interacting with a heavy and ultralight dark photon, through an electric dipole moment, and exclusively with electrons. For a dark-…
Above a critical dark matter-nucleus scattering cross section any terrestrial direct detection experiment loses sensitivity to dark matter, since the Earth crust, atmosphere, and potential shielding layers start to block off the dark matter particles. This critical cross section is commonly determined by describing the average energy loss of the dark matter particles analytically. However, this treatment overestimates the stopping power of the Earth crust. Therefore the obtained bounds should be considered as conservative. We perform Monte Carlo simulations to determine the precise value of th…
We study the direct detection prospects for a representative set of simplified models of sub-GeV dark matter (DM), accounting for existing terrestrial, astrophysical and cosmological constraints. We focus on dark matter lighter than an MeV, where these constraints are most stringent, and find three scenarios with accessible direct detection cross sections: (i) DM interacting via an ultralight kinetically mixed dark photon, (ii) a DM sub-component interacting with nucleons or electrons through a light scalar or vector mediator, and (iii) DM coupled with nucleons via a mediator heavier than ~ 10…
We study self-interacting dark matter signatures at the Large Hadron Collider. A light dark photon, mediating dark matter self-interactions, can bind dark matter particles to form a bound state when they are produced via a heavy pseduoscalar in $pp$ collisions. The bound state can further annihilate into a pair of boosted dark photons, which subsequently decay into charged leptons through a kinetic mixing portal, resulting in striking displaced lepton jet signals. After adapting the analysis used in the ATLAS experiment, we explore the reach of the model parameters at the $13~{\rm TeV}$ run wi…
Self-interacting dark matter (SIDM) with a light mediator is a promising scenario to alleviate the small-scale problems of the cold dark matter paradigm while being consistent with the latter at large scales, as suggested by astrophysical observations. This, however, leads to an under-abundant SIDM relic due to large annihilation rates into mediator particles, often requiring an extension of the simplest thermal or non-thermal relic generation mechanism. In this work, we consider a singlet-doublet fermion dark matter scenario where the singlet fermion with a light scalar mediator gives rise to…
The Gamma Factory is a proposal to back-scatter laser photons off a beam of partially-stripped ions at the LHC, producing a beam of $\sim 10$ MeV to $1$ GeV photons with intensities of $10^{16}$ to $10^{18}~\text{s}^{-1}$. This implies $\sim 10^{23}$ to $10^{25}$ photons on target per year, many orders of magnitude greater than existing accelerator light sources and also far greater than all current and planned electron and proton fixed target experiments. We determine the Gamma Factory's discovery potential through "dark Compton scattering," $γe \to e X$, where $X$ is a new, weakly-interactin…
Direct searches for dark matter lead to serious problems for simple models with stable neutral Weakly Interacting Massive Particles (WIMPs) as candidates for dark matter. A possibility is discussed that new stable quarks and charged leptons exist and are hidden from detection, being bound in neutral dark atoms of composite dark matter. Stable -2 charged particles $O^{--}$ are bound with primordial helium in O-helium (OHe) atoms, being specific nuclear interacting form of composite Warmer than Cold dark matter. Slowed down in the terrestrial matter, OHe is elusive for direct methods of undergro…
Neutrino mass constraints in interacting dark energy models after DESI DR2
College of Sciences, Northeastern University（东北大学理学院）；Shenyang Institute of Engineering（沈阳工程学院）；College of Physical Science and Technology, Shenyang Normal University（沈阳师范大学物理科学与技术学院）；MOE Key Laboratory of Data Analytics and Optimization for Smart Industry, Northeastern University（东北大学智能工业数据优化与分析教育部重点实验室）；National Frontiers Science Center for Industrial Intelligence and Systems Optimization, Northeastern University（东北大学工业智能与系统优化前沿科学中心）
