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Dark matter (DM) models with a conserved particle-antiparticle number, $n_{\chi }-n_{\tilde{\chi }}$ , and the asymmetry in the cosmological abundance $n_{\chi }\ne n_{\tilde{\chi }}$ , are known to be challenged by the existence of old neutron stars (NSs), as the sufficient accumulation of DM will lead to the collapse of NSs into black holes. We demonstrate that the applicability of these constraints is much wider and covers models with symmetric populations of DM, $n_{\chi }=n_{\tilde{\chi }}$ , as the process of DM capture regulated by a nucleon-DM scattering can be inherently asymmetric, ${\sigma }_{\chi n}\ne {\sigma }_{\tilde{\chi }n}$ . The asymmetry is induced by the interference of different types of $\chi \text{−}n$ interactions, provided that their combination is odd under charge conjugation in the DM sector, $C_{\chi }$ , and even under combined parity $P_{\chi +n}$ . We provide a complete analysis of DM-nucleon bilinear $\chi \text{−}n$ interactions and find that this asymmetry is very generic. Using canonical NS parameters and local DM halo inputs, we exclude spin-averaged scattering cross sections down to ${\sigma }_{n\chi }\gtrsim {10}^{-46}{\mathrm{cm}}^2$ at DM mass $m_{\chi }\lesssim {10}^{10}\mathrm{GeV}$ for the maximally asymmetric capture rate and show that the constraints persist down to very small values of the cross-section asymmetry, $\mathcal{A}=({\sigma }_{\chi n}-{\sigma }_{\tilde{\chi }n})/({\sigma }_{\chi n}+{\sigma }_{\tilde{\chi }n})\gtrsim {10}^{-5}$ . 

Axionlike particles (ALPs) are well-motivated examples of light, weakly coupled particles in theories beyond the Standard Model. In this work, we study long-lived ALPs coupled exclusively to leptons in the mass range between $2m_e$ and $m_{\tau }-m_e$ . For anarchic flavor structure the leptophilic ALP production in tau decays or from ALP-tau bremsstrahlung is enhanced thanks to derivative couplings of the ALP and can surpass production from electron and muon channels, especially for ALPs heavier than $m_{\mu }$ . Using past data from high-energy fixed-target experiments such as CHARM and BEBC we place new constraints on the ALP decay constant $f_a$ , reaching scales as high as $\mathcal{O}\left({10}^8\right)\mathrm{GeV}$ in lepton-flavor-violating channels and $f_a\sim \mathcal{O}\left({10}^2\right)\mathrm{GeV}$ in lepton-flavor-conserving ones. We also present projections for the event-rate sensitivity of current and future detectors to ALPs produced at the Fermilab Main Injector, the CERN SPS, and in the forward direction of the LHC. We show that SHiP will be sensitive to $f_a$ values that are over an order of magnitude above the existing constraints. 

WIMP-type dark matter may have additional interactions that break baryon number, leading to induced nucleon decays which are subject to direct experimental constraints from proton decay experiments. In this work, we analyze the possibility of continuous baryon destruction, deriving strong limits from the dark matter accumulating inside old neutron stars, as such a process leads to excess heat generation. We construct the simplest particle dark matter model that breaks the baryon and lepton numbers separately but conserves $B-L$ . Virtual exchange by DM particles in this model results in dinucleon decay via $nn\to n\overline{\nu }$ and $np\to n{e}^{+}$ processes. Published by the American Physical Society2025 

A<sc>bstract</sc> Strongly-interacting dark matter can be accumulated in large quantities inside the Earth, and for dark matter particles in a few GeV mass range, it can exist in large quantities near the Earth’s surface. We investigate the constraints imposed on such dark matter properties by its upscattering by fast neutrons in nuclear reactors with subsequent scattering in nearby well-shielded dark matter detectors, schemes which are already used for searches of the coherent reactor neutrino scattering. We find that the existing experiments cover new parameter space on the spin-dependent interaction between dark matter and the nucleon. Similar experiments performed with research reactors, and lesser amount of shielding, may provide additional sensitivity to strongly-interacting dark matter. 

Abstract A sub-component of dark matter with a short collision length compared to a planetary size leads to efficient accumulation of dark matter in astrophysical bodies. We analyze possible neutrino signals from the annihilation of such dark matter and conclude that in the optically thick regime for dark matter capture, the Earth provides the largest neutrino flux. Using the results of the existing searches, we consider two scenarios for the neutrino flux, from stopped mesons and prompt higher-energy neutrinos. In both cases we exclude some previously unexplored parts of the parameter space (dark matter mass, its abundance, and the scattering cross section on nuclei) by recasting the existing neutrino searches. 

ABSTRACT The largest uncertainty on measurements of dark energy using type Ia supernovae (SNeIa) is presently due to systematics from photometry; specifically to the relative uncertainty on photometry as a function of wavelength in the optical spectrum. We show that a precise constraint on relative photometry between the visible and near-infrared can be achieved at upcoming survey telescopes, such as at the Vera C. Rubin Observatory, via a laser source tuned to the 342.78 nm vacuum excitation wavelength of neutral sodium atoms. Using a high-power laser, this excitation will produce an artificial star, which we term a ‘laser photometric ratio star’ (LPRS) of de-excitation light in the mesosphere at wavelengths in vacuum of 589.16, 589.76, 818.55, and 819.70 nm, with the sum of the numbers of 589.16 and 589.76 nm photons produced by this process equal to the sum of the numbers of 818.55 and 819.70 nm photons, establishing a precise calibration ratio between, for example, the r and $$z$$ filters of the LSST camera at the Rubin Observatory. This technique can thus provide a novel mechanism for establishing a spectrophotometric calibration ratio of unprecedented precision for upcoming telescopic observations across astronomy and atmospheric physics; thus greatly improving the performance of upcoming measurements of dark energy parameters using type SNeIa. The second paper of this pair describes an alternative technique to achieve a similar, but brighter, LPRS than the technique described in this paper, by using two lasers near resonances at 589.16 and 819.71 nm, rather than the single 342.78 nm on-resonance laser technique described in this paper.