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1.
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Search for heavy neutral leptons in $\pi^+$ decays to positrons
/ Bloch-Devaux, Brigitte (Louvain U., CP3 ; Birmingham U.) ; Cortina Gil, Eduardo (Louvain U., CP3) ; Minucci, Elisa (Louvain U., CP3 ; Frascati) ; Padolski, Sergey (Louvain U., CP3) ; Petrov, Plamen (Louvain U., CP3) ; Numao, Toshio (TRIUMF) ; Petrov, Yevgeniy (TRIUMF) ; Velghe, Bob (TRIUMF) ; Wong, Vincent Wai Sum (TRIUMF) ; Shang, Victor (TRIUMF) et al.
A search for heavy neutral lepton ($N$) production in $\pi^+\to e^+ N$ in-flight decays using data collected by the NA62 experiment at CERN in 2017-2024 is reported. Upper limits for the extended neutrino mixing matrix element $|U_{e4}|^2$ are established at the level of $10^{-8}$ for heavy neutral leptons with mass in the range 95-126 MeV/$c^2$ and lifetime exceeding 50 ns..
arXiv:2507.07345; CERN-EP-2025-152.-
Geneva : CERN, 2025 - 16 p.
Draft (restricted): PDF; Fulltext: CERN-EP-2025-152 - PDF; 2507.07345 - PDF;
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2.
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Searches for hidden sectors using $K^+\to\pi^+X$ decays
/ Cortina Gil, Eduardo (Louvain U., CP3) ; Jerhot, Jan (Louvain U., CP3 ; Munich, Max Planck Inst.) ; Minucci, Elisa (Louvain U., CP3 ; Frascati) ; Padolski, Sergey (Louvain U., CP3) ; Petrov, Plamen (Louvain U., CP3) ; Shaikhiev, Artur (Louvain U., CP3 ; Lancaster U.) ; Volpe, Roberta (Louvain U., CP3 ; INFN, Perugia) ; Numao, Toshio (TRIUMF) ; Petrov, Yevgeniy (TRIUMF) ; Velghe, Bob (TRIUMF) et al.
Results from the study of the rare decays $K^+\to\pi^+\nu\bar{\nu}$, $K^{+}\to \pi^{+}\mu^{+}\mu^{-}$ and $K^{+}\to\pi^{+}\gamma\gamma$ at the NA62 experiment at CERN are interpreted in terms of improved limits for $B(K^+\to\pi^+X)$ and coupling parameters of hidden-sector models, where X is a mediator. World-leading limits are achieved for dark photon, dark scalar and axion-like particle models..
arXiv:2507.17286; CERN-EP-2025-167.-
Geneva : CERN, 2025 - 25 p.
Draft (restricted): PDF; Fulltext: CERN-EP-2025-167 - PDF; 2507.17286 - PDF;
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3.
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Search for hadronic decays of feebly-interacting particles at NA62
/ NA62 Collaboration
The NA62 experiment at CERN has the capability to collect data in a beam-dump mode, where 400 GeV protons are dumped on an absorber. In this configuration, New Physics particles, including dark photons, dark scalars, and axion-like particles, may be produced in the absorber and decay in the instrumented volume beginning approximately 80 m downstream of the dump. [...]
arXiv:2502.04241; CERN-EP-2025-012.-
Geneva : CERN, 2025-05-25 - 17 p.
- Published in : Eur. Phys. J. C 85 (2025) 571
Draft (restricted): PDF; Fulltext: CERN-EP-2025-012 - PDF; 2502.04241 - PDF; document - PDF;
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4.
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Observation of the $K^+ \to \pi^+ \nu \bar\nu$ decay and measurement of its branching ratio
/ Cortina Gil, Eduardo (Louvain U., CP3) ; Jerhot, Jan (Louvain U., CP3 ; Munich, Max Planck Inst.) ; Lurkin, Nicolas (Louvain U., CP3) ; Numao, Toshio (TRIUMF) ; Velghe, Bob (TRIUMF) ; Wong, Vincent Wai Sum (TRIUMF) ; Bryman, Douglas (British Columbia U. ; TRIUMF) ; Hives, Zdenko (Charles U.) ; Husek, Tomas (Charles U. ; Birmingham U.) ; Kampf, Karol (Charles U.) et al.
A measurement of the $K^+ \to \pi^+ \nu \bar\nu$ decay by the NA62 experiment at the CERN SPS is presented, using data collected in 2021 and 2022. This dataset was recorded, after modifications to the beamline and detectors, at a higher instantaneous beam intensity with respect to the 2016–2018 data taking. [...]
arXiv:2412.12015; CERN-EP-2024-343.-
Geneva : CERN, 2025-02-27 - 29 p.
- Published in : JHEP 2502 (2025) 191
Draft (restricted): PDF; Fulltext: CERN-EP-2024-343 - PDF; 2412.12015 - PDF; document - PDF;
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5.
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First detection of a tagged neutrino in the NA62 experiment
/ NA62 Collaboration
The NA62 experiment at the CERN SPS reports the first detection of a tagged neutrino candidate based on the data collected in 2022. The candidate consists of a $K^+ \rightarrow \mu^+ \nu_{\mu}$ decay where the charged particles are reconstructed and the neutrino is detected through a charged-current interaction in a liquid krypton calorimeter..
arXiv:2412.04033; CERN-EP-2024-324.-
Geneva : CERN, 2025-02-27 - 16 p.
- Published in : Phys. Lett. B 863 (2025) 139345
Draft (restricted): PDF; Fulltext: PDF; preprint: PDF; publication: PDF;
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6.
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Study of the rare decay $J\mskip -3mu/\mskip -2mu\psi \to \mu^+\mu^-\mu^+\mu^-$
/ LHCb Collaboration
The rare electromagnetic $J\mskip -3mu/\mskip -2mu\psi \to \mu^+\mu^-\mu^+\mu^-$ decay is observed with a significance greatly exceeding the discovery threshold, using proton-proton collision data collected by the LHCb experiment during 2016--2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4\,\text{fb}^{-1}$. The rate of this decay is measured relative to that of the $J\mskip -3mu/\mskip -2mu\psi \to \mu^+\mu^-$ mode. [...]
arXiv:2408.16646; LHCb-PAPER-2024-016; CERN-EP-2024-201; LHCB-PAPER-2024-016.-
Geneva : CERN, 2024-12-10 - 26 p.
- Published in : JHEP 2412 (2024) 062
Fulltext: LHCb-PAPER-2024-016_arxiv - PDF; 2408.16646 - PDF; document - PDF; Related data file(s): ZIP;
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7.
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First search for $K^+ \to \pi^0 \pi \mu e$ decays
/ NA62 Collaboration
The first search for the lepton number violating decay $K^+ \to \pi^0 \pi^- \mu^+ e^+$ and lepton flavour violating decays $K^+ \to \pi^0 \pi^+ \mu^- e^+$, $K^+ \to \pi^0 \pi^+ \mu^+ e^-$ has been performed using a dataset collected by the NA62 experiment at CERN in 2016–2018. Upper limits of $2.9\times 10^{-10}$, $3.1 \times 10^{-10}$ and $5.0 \times 10^{-10}$, respectively, are obtained at 90% CL for the branching ratios of the three decays on the assumption of uniform phase-space distributions..
arXiv:2409.12981; CERN-EP-2024-224.-
Geneva : CERN, 2024-11-12 - 9 p.
- Published in : Phys. Lett. B 859 (2024) 139122
Draft (restricted): PDF; Fulltext: CERN-EP-2024-224 - PDF; 2409.12981 - PDF; Publication - PDF;
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8.
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CEPC Technical Design Report: Accelerator
/ CEPC Study Group Collaboration
The Circular Electron Positron Collider (CEPC) is a large scientific project initiated and hosted by China, fostered through extensive collaboration with international partners. The complex comprises four accelerators: a 30 GeV Linac, a 1.1 GeV Damping Ring, a Booster capable of achieving energies up to 180 GeV, and a Collider operating at varying energy modes (Z, W, H, and ttbar). [...]
arXiv:2312.14363; IHEP-CEPC-DR-2023-01; IHEP-AC-2023-01.-
2024-12-16 - 9 p.
- Published in : Radiat. Detect. Technol. Methods: 8 (2024) , no. 1, pp. 1-1105
Fulltext: 2312.14363 - PDF; Publication - PDF; document - PDF;
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9.
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Development of a new CEDAR for kaon identification at the NA62 experiment at CERN
/ NA62 Collaboration
The NA62 experiment at CERN utilises a differential Cherenkov counter with achromatic ring focus (CEDAR) for tagging kaons within an unseparated monochromatic beam of charged hadrons. The CEDAR-H detector was developed to minimise the amount of material in the path of the beam by using hydrogen gas as the radiator medium. [...]
arXiv:2312.17188; CERN-EP-2023-302.-
Geneva : CERN, 2024-05-07 - 20 p.
- Published in : JINST 19 (2024) P05005
Draft (restricted): PDF; Fulltext: CERN-EP-2023-302 - PDF; 2312.17188 - PDF; document - PDF;
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10.
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