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1. Search for a light sterile neutrino with 7.5 years of IceCube DeepCore data

   https://doi.org/10.1103/PhysRevD.110.072007  

   Abbasi, R; Ackermann, M; Adams, J; Agarwalla, S K; Aguilar, J A; Ahlers, M; Alameddine, J M; Amin, N M; Andeen, K; Argüelles, C; et al (October 2024, Physical Review D)

   We present a search for an eV-scale sterile neutrino using 7.5 years of data from the IceCube DeepCore detector. The analysis uses a sample of 21,914 events with energies between 5 and 150 GeV to search for sterile neutrinos through atmospheric muon neutrino disappearance. Improvements in event selection and treatment of systematic uncertainties provide greater statistical power compared to previous DeepCore sterile neutrino searches. Our results are compatible with the absence of mixing between active and sterile neutrino states, and we place constraints on the mixing matrix elements $|U_{\mu 4}{|}^2<0.0534$ and $|U_{\tau 4}{|}^2<0.0574$ at 90% CL under the assumption that $\mathrm{\Delta }{m}_{41}^2\ge 1{\mathrm{eV}}^2$ . These null results add to the growing tension between anomalous appearance results and constraints from disappearance searches in the $3+1$ sterile neutrino landscape. Published by the American Physical Society2024 

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2. Search for proton decay via $p\to e^{+}\eta$ and $p\to {\mu }^{+}\eta$ with a 0.37 Mton-year exposure of Super-Kamiokande

   https://doi.org/10.1103/PhysRevD.110.112011  

   Taniuchi, N; Abe, K; Abe, S; Asaoka, Y; Bronner, C; Harada, M; Hayato, Y; Hiraide, K; Hosokawa, K; Ieki, K; et al (December 2024, Physical Review D)

   A search for proton decay into $e^{+}/{\mu }^{+}$ and a $\eta$ meson has been performed using data from a $0.373\mathrm{Mton}·\mathrm{year}$ exposure (6050.3 live days) of Super-Kamiokande. Compared to previous searches this work introduces an improved model of the intranuclear $\eta$ interaction cross section, resulting in a factor of 2 reduction in uncertainties from this source and $\sim 10\%$ increase in signal efficiency. No significant data excess was found above the expected number of atmospheric neutrino background events resulting in no indication of proton decay into either mode. Lower limits on the proton partial lifetime of $1.4\times {10}^{34}\mathrm{years}$ for $p\to e^{+}\eta$ and $7.3\times {10}^{33}\mathrm{years}$ for $p\to {\mu }^{+}\eta$ at the 90% CL were set. These limits are around 1.5 times longer than our previous study and are the most stringent to date. Published by the American Physical Society2024 

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3. Combination of Searches for Resonant Higgs Boson Pair Production Using $pp$ Collisions at $\sqrt{s}=13\mathrm{TeV}$ with the ATLAS Detector

   https://doi.org/10.1103/PhysRevLett.132.231801  

   Aad, G; Aakvaag, E; Abbott, B; Abeling, K; Abicht, N J; Abidi, S H; Aboulhorma, A; Abramowicz, H; Abreu, H; Abulaiti, Y; et al (June 2024, Physical Review Letters)

   A combination of searches for a new resonance decaying into a Higgs boson pair is presented, using up to $139{\mathrm{fb}}^{-1}$ of $pp$ collision data at $\sqrt{s}=13\mathrm{TeV}$ recorded with the ATLAS detector at the LHC. The combination includes searches performed in three decay channels: $b\overline{b}b\overline{b}$ , $b\overline{b}{\tau }^{+}{\tau }^{-}$ , and $b\overline{b}\gamma \gamma$ . No excess above the expected Standard Model background is observed and upper limits are set at the 95% confidence level on the production cross section of Higgs boson pairs originating from the decay of a narrow scalar resonance with mass in the range 251 GeV–5 TeV. The observed (expected) limits are in the range 0.96–600 fb (1.2–390 fb). The limits are interpreted in the type-I two-Higgs-doublet model and the minimal supersymmetric standard model, and constrain parameter space not previously excluded by other searches. © 2024 CERN, for the ATLAS Collaboration2024CERN 

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4. Search for a heavy neutral lepton that mixes predominantly with the tau neutrino

   https://doi.org/10.1103/PhysRevD.109.L111102  

   Nayak, M; Dey, S; Soffer, A; Adachi, I; Aihara, H; Al_Said, S; Asner, D M; Atmacan, H; Ayad, R; Babu, V; et al (June 2024, Physical Review D)

   We report a search for a heavy neutral lepton (HNL) that mixes predominantly with ${\nu }_{\tau }$ . The search utilizes data collected with the Belle detector at the KEKB asymmetric energy $e^{+}{e}^{-}$ collider. The data sample was collected at and just below the center-of-mass energies of the $\mathrm{\Upsilon }\left(4S\right)$ and $\mathrm{\Upsilon }\left(5S\right)$ resonances and has an integrated luminosity of $915{\mathrm{fb}}^{-1}$ , corresponding to $(836\pm 12)\times {10}^6$ $e^{+}{e}^{-}\to {\tau }^{+}{\tau }^{-}$ events. We search for production of the HNL (denoted $N$ ) in the decay ${\tau }^{-}\to {\pi }^{-}N$ followed by its decay via $N\to {\mu }^{+}{\mu }^{-}{\nu }_{\tau }$ . The search focuses on the parameter-space region in which the HNL is long-lived, so that the ${\mu }^{+}{\mu }^{-}$ originate from a common vertex that is significantly displaced from the collision point of the KEKB beams. Consistent with the expected background yield, one event is observed in the data sample after application of all the event-selection criteria. We report limits on the mixing parameter of the HNL with the $\tau$ neutrino as a function of the HNL mass. Published by the American Physical Society2024 

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5. Observation of the $J/\psi \to {\mu }^{+}{\mu }^{-}{\mu }^{+}{\mu }^{-}$ decay in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$

   https://doi.org/10.1103/PhysRevD.109.L111101  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Hussain, P S; Jeitler, M; et al (June 2024, Physical Review D)

   The $J/\psi \to {\mu }^{+}{\mu }^{-}{\mu }^{+}{\mu }^{-}$ decay has been observed with a statistical significance in excess of five standard deviations. The analysis is based on an event sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the CMS experiment in 2018 and corresponding to an integrated luminosity of $33.6{\mathrm{fb}}^{-1}$ . Normalizing to the $J/\psi \to {\mu }^{+}{\mu }^{-}$ decay mode leads to a branching fraction of $[{10.1}_{-2.7}^{+3.3}\left(\mathrm{stat}\right)\pm 0.4\left(\mathrm{syst}\right)]\times {10}^{-7}$ , a value that is consistent with the standard model prediction. © 2024 CERN, for the CMS Collaboration2024CERN 

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