CERN Accelerating science

CERN Document Server 2,048 εγγραφές βρέθηκαν  1 - 10επόμενοτέλος  μετάβαση στην εγγραφή: Η έρευνα πήρε 2.81 δευτερόλεπτα. 
1.
Measurement of the $K^+ \to \pi^+ \gamma \gamma$ decay / NA62 Collaboration
A sample of 3984 candidates of the $K^+ \to \pi^+ \gamma \gamma$ decay, with an estimated background of $291 \pm 14$ events, was collected by the NA62 experiment at CERN during 2017–2018. In order to describe the observed di-photon mass spectrum, the next-to-leading order contribution in chiral perturbation theory was found to be necessary. [...]
arXiv:2311.01837; CERN-EP-2023-247.- Geneva : CERN, 2024-02-07 - 11 p. - Published in : Phys. Lett. B 850 (2024) 138513 Draft (restricted): PDF; Fulltext: CERN-EP-2023-247 - PDF; 2311.01837 - PDF; Publication - PDF;
2.
Search for $K^+$ decays into the $\pi^+e^+e^-e^+e^-$ final state / NA62 Collaboration
The first search for ultra-rare $K^+$ decays into the $\pi^+e^+e^-e^+e^-$ final state is reported, using a dataset collected by the NA62 experiment at CERN in 2017-2018. An upper limit of $1.4\times 10^{-8}$ at 90% CL is obtained for the branching ratio of the $K^+\to\pi^+e^+e^-e^+e^-$ decay, predicted in the Standard Model to be $(7.2 \pm0 .7)\times 10^{-11}$. [...]
arXiv:2307.04579; CERN-EP-2023-133.- Geneva : CERN, 2023-09-22 - 9 p. - Published in : Phys. Lett. B 846 (2023) 138193 Draft (restricted): PDF; Fulltext: CERN-EP-2023-133 - PDF; Publication - PDF; 2307.04579 - PDF;
3.
A search for the $K^+ \to \mu^- \nu e^+ e^+$ decay / NA62 Collaboration
A search for the $K^+ \to \mu^- \nu e^+ e^+$ decay forbidden within the Standard Model by either lepton number or lepton flavour conservation depending on the flavour of the emitted neutrino, has been performed using the dataset collected by the NA62 experiment at CERN in 2016–2018. An upper limit of $8.1 \times 10^{-11}$ is obtained for the decay branching fraction at 90% CL, improving by a factor of 250 over the previous search..
arXiv:2211.04818; CERN-EP-2022-243.- Geneva : CERN, 2023-03-10 - 12 p. - Published in : Phys. Lett. B 838 (2023) 137679 Draft (restricted): PDF; Fulltext: 2211.04818 - PDF; Publication - PDF; CERN-EP-2022-243 - PDF;
4.
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;
5.
Search for heavy neutral lepton production in $K^+$ decays to positrons / NA62 Collaboration
A search for heavy neutral lepton ($N$) production in $K^+\to e^+N$ decays using the data sample collected by the NA62 experiment at CERN in 2017--2018 is reported. Upper limits of the extended neutrino mixing matrix element $|U_{e4}|^2$ are established at the level of $10^{-9}$ over most of the accessible heavy neutral lepton mass range 144--462 MeV/$c^2$, with the assumption that the lifetime exceeds 50 ns. [...]
arXiv:2005.09575; CERN-EP-2020-089.- Geneva : CERN, 2020-07-02 - 9 p. - Published in : Phys. Lett. B 807 (2020) 135599 Article from SCOAP3: PDF; Fulltext: 2005.09575 - PDF; CERN-EP-DRAFT-NA62-2020-001 - PDF;
6.
Search for lepton number and flavour violation in $K^+ $ and $\pi^0$ decays / NA62 Collaboration
Searches for the lepton number violating $K^+ \to \pi^− \mu^+ e^+$ decay and the lepton flavour violating $K^+ \to \pi^+ \mu^- e^+$ and $\pi^0 \to \mu^- e^+$ decays are reported using data collected by the NA62 experiment at CERN in 2017$-$2018. No evidence for these decays is found and upper limits of the branching ratios are obtained at 90% confidence level: B($K^+ \to \pi^− \mu^+ e^+$) $< 4.2 \times 10^{−11}$, B($K^+ \to \pi^+ \mu^- e^+$) $< 6.6 \times 10^{−11}$ and B($\pi^0 \to \mu^- e^+$) $< 3.2 \times 10^{−10}$. [...]
arXiv:2105.06759; CERN-EP-2021-090.- Geneva : CERN, 2021-09-24 - 8 p. - Published in : Phys. Rev. Lett. 127 (2021) 131802 Draft (restricted): PDF; Fulltext: 2105.06759 - PDF; CERN-EP-2021-090 - PDF; Publication - PDF; Fulltext from publisher: PDF;
7.
Searches for lepton number violating $K^+\to\pi^-(\pi^0)e^+e^+$ decays / NA62 Collaboration
Searches for lepton number violating $K^+\to\pi^-e^+e^+$ and $K^+\to\pi^-\pi^0e^+e^+$ decays have been performed using the complete dataset collected by the NA62 experiment at CERN in 2016-2018. Upper limits of $5.3\times 10^{-11}$ and $8.5\times 10^{-10}$ are obtained on the decay branching fractions at 90% confidence level. [...]
arXiv:2202.00331; CERN-EP-2022-018.- 2022-07-10 - 16 p. Draft (restricted): PDF; Fulltext: 2202.00331 - PDF; CERN-EP-2022-018 - PDF;
8.
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: CERN-EP-2024-324 - PDF; 2412.04033 - PDF;
9.
Search for leptonic decays of dark photons at NA62Search for Leptonic Decays of Dark Photons at NA62 / NA62 Collaboration
The NA62 experiment at CERN, configured in beam-dump mode, has searched for dark photon decays in flight to electron-positron pairs using a sample of $1.4 \times 10^{17}$ protons on dump collected in 2021. No evidence for a dark photon signal is observed. [...]
arXiv:2312.12055; CERN-EP-2023-296.- Geneva : CERN, 2024-09-11 - 10 p. - Published in : Phys. Rev. Lett. 133 (2024) 111802 Draft (restricted): PDF; Fulltext: CERN-EP-2023-296 - PDF; 2312.12055 - PDF; Publication - PDF;
10.
Improved measurement of $CP$ violation parameters in $B_s^0\to J/\psi K^+K^-$ decays in the vicinity of the $\phi(1020)$ resonance / LHCb Collaboration
The decay-time-dependent $CP$ asymmetry in $B_s^0\to J/\psi(\to \mu^+\mu^-) K^+ K^-$ decays is measured using proton-proton collision data, corresponding to an integrated luminosity of $6 {\rm fb}^{-1}$, collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 $B_s^0$ signal decays with an invariant $K^+ K^-$ mass in the vicinity of the $\phi(1020)$ resonance, the $CP$-violating phase $\phi_s$ is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the $B_s^0$-$\overline{B}_s^0$ system, $\Delta\Gamma_s$, and the difference of the average $B_s^0$ and $B^0$ meson decay widths, $\Gamma_s-\Gamma_d$. [...]
arXiv:2308.01468; LHCb-PAPER-2023-016; CERN-EP-2023-145; CERN-EP-2023-145 CERN-EP-2023-145; LHCb-PAPER-2023-016.- Geneva : CERN, 2024-02-02 - 12 p. - Published in : Phys. Rev. Lett. 132 (2024) 051802 Fulltext: 2308.01468 - PDF; Publication - PDF; Related data file(s): ZIP; Supplementary information: ZIP;

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