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1. Primordial Black Hole Dark Matter Simulations Using PopSyCLE

   https://doi.org/10.3847/1538-4357/ad3df0  

   Pruett, Kerianne; Dawson, William; Medford, Michael S; Lu, Jessica R; Lam, Casey; Perkins, Scott; McGill, Peter; Golovich, Nathan; Chapline, George (July 2024, The Astrophysical Journal)

   Abstract Primordial black holes (PBHs), theorized to have originated in the early Universe, are speculated to be a viable form of dark matter. If they exist, they should be detectable through photometric and astrometric signals resulting from gravitational microlensing of stars in the Milky Way. Population Synthesis for Compact-object Lensing Events, orPopSyCLE, is a simulation code that enables users to simulate microlensing surveys, and is the first of its kind to include both photometric and astrometric microlensing effects, which are important for potential PBH detection and characterization. To estimate the number of observable PBH microlensing events, we modifyPopSyCLEto include a dark matter halo consisting of PBHs. We detail our PBH population model, and demonstrate ourPopSyCLE+ PBH results through simulations of the Optical Gravitational Lensing Experiment-IV (OGLE-IV) and Nancy Grace Roman Space Telescope (Roman) microlensing surveys. We provide a proof-of-concept analysis for adding PBHs intoPopSyCLE, and thus include many simplifying assumptions, such asf_DM, the fraction of dark matter composed of PBHs, and ${\overline{m}}_{\mathrm{PBH}}$, mean PBH mass. Assuming ${\overline{m}}_{\mathrm{PBH}}=30$M_⊙, we find ∼3.6f_DMtimes as many PBH microlensing events than stellar evolved black hole events, a PBH average peak Einstein crossing time of ∼91.5 days, estimate on order of 10²f_DMPBH events within the 8 yr OGLE-IV results, and estimate Roman to detect ∼1000f_DMPBH microlensing events throughout its planned microlensing survey. 

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2. More on black holes perceiving the dark dimension

   https://doi.org/10.1103/PhysRevD.110.015004  

   Anchordoqui, Luis A; Antoniadis, Ignatios; Lüst, Dieter (July 2024, Physical Review D)

   In the last two years, the dark dimension scenario has emerged as focal point of many research interests. In particular, it functions as a stepping stone to address the cosmological hierarchy problem and provides a colosseum for dark matter contenders. We reexamine the possibility that primordial black holes (PBHs) perceiving the dark dimension could constitute all of the dark matter in the Universe. We reassess limits on the abundance of PBHs as dark matter candidates from $\gamma$-ray emission resulting from Hawking evaporation. We reevaluate constraints from the diffuse $\gamma$-ray emission in the direction of the Galactic Center that offer the best and most solid upper limits on the dark matter fraction composed of PBHs. The revised mass range that allows PBHs to assemble all cosmological dark matter is estimated to be ${10}^{15}\lesssim M_{\mathrm{BH}}/\mathrm{g}\lesssim {10}^{21}$. We demonstrate that, due to the constraints from $\gamma$-ray emission, quantum corrections due to the speculative memory burden effect do not modify this mass range. We also investigate the main characteristics of PBHs that are localized in the bulk. We show that PBHs localized in the bulk can make all cosmological dark matter if ${10}^{11}\lesssim M_{\mathrm{BH}}/\mathrm{g}\lesssim {10}^{21}$. Finally, we comment on the black holes that could be produced if one advocates a space with two boundaries for the dark dimension. Published by the American Physical Society2024 

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3. Indirect detection of hot dark matter

   https://doi.org/10.1007/JHEP05(2025)127  

   Dror, Jeff A; Sandick, Pearl; Haghi, Barmak_Shams Es; Yang, Fengwei (May 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> Cosmologically stable, light particles that came into thermal contact with the Standard Model in the early universe may persist today as a form of hot dark matter. For relics with masses in the eV range, their role in structure formation depends critically on their mass. We trace the evolution of such hot relics and derive their density profiles around cold dark matter halos, introducing a framework for theirindirect detection. Applying this framework to axions — a natural candidate for a particle that can reach thermal equilibrium with the Standard Model in the early universe and capable of decaying into two photons — we establish stringent limits on the axion-photon couplingg_aγusing current observations of dwarf galaxies, the Milky Way halo, and galaxy clusters. Our results set new bounds on hot axions in the$$ \mathcal{O}\left(1-10\right) $$ $O\left(1-10\right)$eV range. 

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4. Hawking radiation of nonrelativistic scalars: applications to pion and axion production

   https://doi.org/10.1007/JHEP11(2024)071  

   Cui, Hao-Ran; Tsai, Yuhsin; Xu, Tao (November 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> In studying secondary gamma-ray emissions from Primordial Black Holes (PBHs), the production of scalar particles like pions and axion-like particles (ALPs) via Hawking radiation is crucial. While previous analyses assumed relativistic production, asteroid-mass PBHs, relevant to upcoming experiments like AMEGO-X, likely produce pions and ALPs non-relativistically when their masses exceed 10 MeV. To account for mass dependence in Hawking radiation, we revisit the greybody factors for massive scalars from Schwarzschild black holes, revealing significant mass corrections to particle production rates compared to the projected AMEGO-X sensitivity. We highlight the importance of considering non-relativisticπ⁰production in interpreting PBH gamma-ray signals, essential for determining PBH properties. Additionally, we comment on the potential suppression of pion production due to form factor effects when producing extended objects via Hawking radiation. We also provide an example code for calculating the Hawking radiation spectrum of massive scalar particles Image missing<#comment/>. 

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5. Probing Benchmark Models of Hidden-Sector Dark Matter with DAMIC-M

   https://doi.org/10.1103/2tcc-bqck  

   Aggarwal, K; Arnquist, I; Avalos, N; Bertou, X; Castelló-Mor, N; Chavarria, A E; Cuevas-Zepeda, J; Dastgheibi-Fard, A; De_Dominicis, C; Deligny, O; et al (August 2025, Physical Review Letters)

   We report on a search for sub-GeV dark matter (DM) particles interacting with electrons using the DAMIC-M prototype detector at the Modane Underground Laboratory. The data feature a significantly lower detector single $e^{-}$rate (factor 50) compared to our previous search, while also accumulating a 10 times larger exposure of $\sim 1.3\mathrm{kg}\text{−}\mathrm{day}$. DM interactions in the skipper charge-coupled devices (CCDs) are searched for as groups of two or three adjacent pixels with a total charge between 2 and $4e^{-}$. We find 144 candidates of $2e^{-}$and 1 candidate of $4e^{-}$, where 141.5 and 0.071, respectively, are expected from background. With no evidence of a DM signal, we place stringent constraints on DM particles with masses between 1 and $1000\mathrm{MeV}/c^2$interacting with electrons through an ultralight or heavy mediator. For large ranges of DM masses below $1\mathrm{GeV}/c^2$, we exclude theoretically motivated benchmark scenarios where hidden-sector particles are produced as a major component of DM in the Universe through the freeze-in or freeze-out mechanisms. 

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