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1. The low-energy spectrum in DAMIC at SNOLAB

   https://doi.org/10.21468/SciPostPhysProc.12.011  

   Chavarria, Alvaro E. (July 2023, SciPost Physics Proceedings)

   The DAMIC experiment employs large-area, thick charge-coupled devices (CCDs) to search for the interactions of low-mass dark matter particles in the galactic halo with silicon atoms in the CCD target. From 2017 to 2019, DAMIC collected data with a seven-CCD array (40-gram target) installed in the SNOLAB underground laboratory. We report dark-matter search results, including a conspicuous excess of events above the background model below 200 V_{ee} V e e , whose origin remains unknown. We present details of the published spectral analysis, and update on the deployment of skipper CCDs to perform a more precise measurement by early 2023. 

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2. 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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3. S8 Tension in the Context of Dark Matter–Baryon Scattering

   https://doi.org/10.3847/2041-8213/acdb63  

   He, Adam; Ivanov, Mikhail M.; An, Rui; Gluscevic, Vera (August 2023, The Astrophysical Journal Letters)

   Abstract We explore an interacting dark matter (IDM) model that allows for a fraction of dark matter (DM) to undergo velocity-independent scattering with baryons. In this scenario, structure on small scales is suppressed relative to the cold DM scenario. Using the effective field theory of large-scale structure, we perform the first systematic analysis of BOSS full-shape galaxy clustering data for the IDM scenario, and we find that this model ameliorates theS₈tension between large-scale structure and Planck data. Adding theS₈prior from the Dark Energy Survey (DES) to our analysis further leads to a mild ∼3σpreference for a nonvanishing DM–baryon scattering cross section, assuming ∼10% of DM is interacting and has a particle mass of 1 MeV. This result produces a modest ∼20% suppression of the linear power atk≲ 1hMpc⁻¹, consistent with other small-scale structure observations. Similar scale-dependent power suppression was previously shown to have the potential to resolveS₈tension between cosmological data sets. The validity of the specific IDM model explored here will be critically tested with upcoming galaxy surveys at the interaction level needed to alleviate theS₈tension. 

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4. DESI 2024 VI: cosmological constraints from the measurements of baryon acoustic oscillations

   https://doi.org/10.1088/1475-7516/2025/02/021  

   Adame, AG; Aguilar, J; Ahlen, S; Alam, S; Alexander, DM; Alvarez, M; Alves, O; Anand, A; Andrade, U; Armengaud, E; et al (February 2025, Journal of Cosmology and Astroparticle Physics)

   Abstract We present cosmological results from the measurement of baryon acoustic oscillations (BAO) in galaxy, quasar and Lyman-αforest tracers from the first year of observations from the Dark Energy Spectroscopic Instrument (DESI), to be released in the DESI Data Release 1. DESI BAO provide robust measurements of the transverse comoving distance and Hubble rate, or their combination, relative to the sound horizon, in seven redshift bins from over 6 million extragalactic objects in the redshift range 0.1 <z< 4.2. To mitigate confirmation bias, a blind analysis was implemented to measure the BAO scales. DESI BAO data alone are consistent with the standard flat ΛCDM cosmological model with a matter density Ω_m=0.295±0.015. Paired with a baryon density prior from Big Bang Nucleosynthesis and the robustly measured acoustic angular scale from the cosmic microwave background (CMB), DESI requiresH₀=(68.52±0.62) km s^-1Mpc^-1. In conjunction with CMB anisotropies fromPlanckand CMB lensing data fromPlanckand ACT, we find Ω_m=0.307± 0.005 andH₀=(67.97±0.38) km s^-1Mpc^-1. Extending the baseline model with a constant dark energy equation of state parameterw, DESI BAO alone requirew=-0.99^+0.15_-0.13. In models with a time-varying dark energy equation of state parametrised byw₀andw_a, combinations of DESI with CMB or with type Ia supernovae (SN Ia) individually preferw₀> -1 andw_a< 0. This preference is 2.6σfor the DESI+CMB combination, and persists or grows when SN Ia are added in, giving results discrepant with the ΛCDM model at the 2.5σ, 3.5σor 3.9σlevels for the addition of the Pantheon+, Union3, or DES-SN5YR supernova datasets respectively. For the flat ΛCDM model with the sum of neutrino mass ∑m_νfree, combining the DESI and CMB data yields an upper limit ∑m_ν< 0.072 (0.113) eV at 95% confidence for a ∑m_ν> 0 (∑m_ν> 0.059) eV prior. These neutrino-mass constraints are substantially relaxed if the background dynamics are allowed to deviate from flat ΛCDM. 

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5. Astrometric Microlensing by Primordial Black Holes with the Roman Space Telescope

   https://doi.org/10.3847/1538-4357/ad3243  

   Fardeen, James; McGill, Peter; Perkins, Scott E; Dawson, William A; Abrams, Natasha S; Lu, Jessica R; Ho, Ming-Feng; Bird, Simeon (April 2024, The Astrophysical Journal)

   Abstract Primordial black holes (PBHs) could explain some fraction of dark matter and shed light on many areas of early-Universe physics. Despite over half a century of research interest, a PBH population has so far eluded detection. The most competitive constraints on the fraction of dark matter comprised of PBHs (f_DM) in the (10⁻⁹–10)M_⊙mass ranges come from photometric microlensing and boundf_DM≲ 10⁻²–10⁻¹. With the advent of the Roman Space Telescope with its submilliarcsecond astrometric capabilities and its planned Galactic Bulge Time Domain Survey (GBTDS), detecting astrometric microlensing signatures will become routine. Compared with photometric microlensing, astrometric microlensing signals are sensitive to different lens masses–distance configurations and contain different information, making it a complimentary lensing probe. At submilliarcsecond astrometric precision, astrometric microlensing signals are typically detectable at larger lens–source separations than photometric signals, suggesting a microlensing detection channel of pure astrometric events. We use a Galactic simulation to predict the number of detectable microlensing events during the GBTDS via this pure astrometric microlensing channel. Assuming an absolute astrometric precision floor for bright stars of 0.1 mas for the GBTDS, we find that the number of detectable events peaks at ≈10³f_DMfor a population of 1M_⊙PBHs and tapers to ≈10f_DMand ≈100f_DMat 10⁻⁴M_⊙and 10³M_⊙, respectively. Accounting for the distinguishability of PBHs from stellar lenses, we conclude the GBTDS will be sensitive to a PBH population atf_DMdown to ≈10⁻¹–10⁻³for (10⁻¹–10²)M_⊙likely yielding novel PBH constraints. 

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