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1. Constraints on metastable superheavy dark matter coupled to sterile neutrinos with the Pierre Auger Observatory

   https://doi.org/10.1103/PhysRevD.109.L081101  

   Abdul_Halim, A; Abreu, P; Aglietta, M; Allekotte, I; Almeida_Cheminant, K; Almela, A; Aloisio, R; Alvarez-Muñiz, J; Ammerman_Yebra, J; Anastasi, G A; et al (April 2024, Physical Review D)

   Dark matter particles could be superheavy, provided their lifetime is much longer than the age of the Universe. Using the sensitivity of the Pierre Auger Observatory to ultrahigh energy neutrinos and photons, we constrain a specific extension of the Standard Model of particle physics that meets the lifetime requirement for a superheavy particle by coupling it to a sector of ultralight sterile neutrinos. Our results show that, for a typical dark coupling constant of 0.1, the mixing angle ${\theta }_m$between active and sterile neutrinos must satisfy, roughly, ${\theta }_m\lesssim 1.5\times {10}^{-6}(M_X/{10}^9\mathrm{GeV}{)}^{-2}$for a mass $M_X$of the dark-matter particle between ${10}^8\mathrm{GeV}$and ${10}^{11}\mathrm{GeV}$. Published by the American Physical Society2024 

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2. First Search for Dark-Trident Processes Using the MicroBooNE Detector

   https://doi.org/10.1103/PhysRevLett.132.241801  

   Abratenko, P; Alterkait, O; Andrade_Aldana, D; Arellano, L; Asaadi, J; Ashkenazi, A; Balasubramanian, S; Baller, B; Barr, G; Barrow, D; et al (June 2024, Physical Review Letters)

   We present a first search for dark-trident scattering in a neutrino beam using a dataset corresponding to $7.2\times {10}^{20}$protons on target taken with the MicroBooNE detector at Fermilab. Proton interactions in the neutrino target at the main injector produce ${\pi }^0$and $\eta$mesons, which could decay into dark-matter (DM) particles mediated via a dark photon $A^{\prime }$. A convolutional neural network is trained to identify interactions of the DM particles in the liquid-argon time projection chamber (LArTPC) exploiting its imagelike reconstruction capability. In the absence of a DM signal, we provide limits at the 90% confidence level on the squared kinematic mixing parameter ${ϵ}^2$as a function of the dark-photon mass in the range $10\le M_{A^{\prime }}\le 400\mathrm{MeV}$. The limits cover previously unconstrained parameter space for the production of fermion or scalar DM particles $\chi$for two benchmark models with mass ratios $M_{\chi }/M_{A^{\prime }}=0.6$and 2 and for dark fine-structure constants $0.1\le {\alpha }_D\le 1$. Published by the American Physical Society2024 

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3. Resonant conversion of axion dark radiation into terahertz electromagnetic radiation in a neutron star magnetosphere

   https://doi.org/10.1103/PhysRevD.110.103020  

   Long, Andrew J; Schiappacasse, Enrico D (November 2024, Physical Review D)

   In the strong magnetic field of a neutron star’s magnetosphere, axions coupled to electromagnetism develop a nonzero probability to convert into photons. Past studies have revealed that the axion-photon conversion can be resonantly enhanced. We recognize that the axion-photon resonance admits two parametrically distinct resonant solutions, which we call the mass-matched resonance and the Euler-Heisenberg assisted resonance. The mass-matched resonance occurs at a point in the magnetosphere where the radially-varying plasma frequency crosses the axion mass ${\omega }_{\mathrm{pl}}\approx m_a$. The Euler-Heisenberg assisted resonance occurs where the axion energy satisfies $\omega \approx (2{\omega }_{\mathrm{pl}}^2/7g_{\gamma \gamma \gamma \gamma }{\overline{B}}^2{)}^{1/2}$. This second resonance is made possible though the strong background magnetic field $\overline{B}$, as well as the nonzero Euler-Heisenberg four-photon self-interaction, which has the coupling $g_{\gamma \gamma \gamma \gamma }=8{\alpha }^2/45m_e^4$. We study the resonant conversion of relativistic axion dark radiation into photons via the Euler-Heisenberg assisted resonance, and we calculate the expected electromagnetic radiation assuming different values for the axion-photon coupling $g_{a\gamma \gamma }$and different amplitudes for the axion flux onto the neutron star ${\mathrm{\Phi }}_a$. We briefly discuss several possible sources of axion dark radiation. Achieving a sufficiently strong axion flux to induce a detectable electromagnetic signal seems unlikely. Published by the American Physical Society2024 

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4. Effective field theory and inelastic dark matter results from XENON1T

   https://doi.org/10.1103/PhysRevD.109.112017  

   Aprile, E; Abe, K; Agostini, F; Ahmed_Maouloud, S; Althueser, L; Andrieu, B; Angelino, E; Angevaare, J R; Antochi, V C; Antón_Martin, D; et al (June 2024, Physical Review D)

   In this work, we expand on the XENON1T nuclear recoil searches to study the individual signals of dark matter interactions from operators up to dimension eight in a chiral effective field theory (ChEFT) and a model of inelastic dark matter (iDM). We analyze data from two science runs of the XENON1T detector totaling $1\mathrm{t}\times \mathrm{yr}$exposure. For these analyses, we extended the region of interest from $[4.9,40.9]{\mathrm{keV}}_{\mathrm{NR}}$to $[4.9,54.4]{\mathrm{keV}}_{\mathrm{NR}}$to enhance our sensitivity for signals that peak at nonzero energies. We show that the data are consistent with the background-only hypothesis, with a small background overfluctuation observed peaking between 20 and $50{\mathrm{keV}}_{\mathrm{NR}}$, resulting in a maximum local discovery significance of $1.7\sigma$for the $\mathrm{Vector}\otimes {\text{Vector}}_{\text{strange}}$ChEFT channel for a dark matter particle of $70\mathrm{GeV}/c^2$and $1.8\sigma$for an iDM particle of $50\mathrm{GeV}/c^2$with a mass splitting of $100\mathrm{keV}/c^2$. For each model, we report 90% confidence level upper limits. We also report upper limits on three benchmark models of dark matter interaction using ChEFT where we investigate the effect of isospin-breaking interactions. We observe rate-driven cancellations in regions of the isospin-breaking couplings, leading to up to 6 orders of magnitude weaker upper limits with respect to the isospin-conserving case. Published by the American Physical Society2024 

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5. Search for prompt production of pentaquarks in charm hadron final states

   https://doi.org/10.1103/PhysRevD.110.032001  

   Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adeva, B; Adinolfi, M; Adlarson, P; Afsharnia, H; Agapopoulou, C; et al (August 2024, Physical Review D)

   A search for hidden-charm pentaquark states decaying to a range of ${\mathrm{\Sigma }}_c\overline{D}$and ${\mathrm{\Lambda }}_c^{+}\overline{D}$final states, as well as doubly charmed pentaquark states to ${\mathrm{\Sigma }}_{c}D$and ${\mathrm{\Lambda }}_c^{+}D$, is made using samples of proton-proton collision data corresponding to an integrated luminosity of $5.7{\mathrm{fb}}^{-1}$recorded by the LHCb detector at $\sqrt{s}=13\mathrm{TeV}$. Since no significant signals are found, upper limits are set on the pentaquark yields relative to that of the ${\mathrm{\Lambda }}_c^{+}$baryon in the ${\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+}$decay mode. The known pentaquark states are also investigated, and their signal yields are found to be consistent with zero in all cases. © 2024 CERN, for the LHCb Collaboration2024CERN 

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