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Search for $K^+$ decays to a lepton and invisible particles
/ NA62 Collaboration
The NA62 experiment at CERN reports searches for
$K^+ \to e^+ N$, $K^+ \to \mu^+ N$ and $K^+ \to \mu^+ X$ decays,
where $N$ and $X$ are massive invisible particles, using the 2016-2018 data set.
The $N$ particle is assumed to be a heavy neutral lepton, and the results are expressed as upper limits
of $O(10^{-9})$ and $O(10^{-8})$ on the neutrino mixing parameter $|U_{e4}|^2$ and $|U_{\mu 4}|^2$,
improving on the earlier searches for heavy neutral lepton production and decays in the kinematically accessible mass range.
The $X$ particle is considered a scalar or vector hidden sector mediator decaying to an invisible final
state, and upper limits of the decay branching fraction for $X$ masses in the range 10-370 MeV/c$^2$ are
reported for the first time, ranging from $O(10^{-5})$ to $O(10^{-7})$.
An upper limit of
$1.0 \cdot 10^{-6}$
is established
at 90\% CL on the
$K^+\to \mu^+ \nu \nu \bar{\nu}$ branching fraction..
2022 - 6 p.
- Published in : PoS DISCRETE2020-2021 (2022) 056
Fulltext: PDF;
In : 7th Symposium on Prospects in the Physics of Discrete Symmetries (DISCRETE 2020-2021), Bergen, Norway, 29 Nov - 3 Dec 2021, pp.056
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Measurement of the very rare $K^+ \to \pi^+ \nu \bar\nu$ decay
/ NA62 Collaboration
The decay $K^+\to\pi^+\nu\bar{\nu}$, with a very precisely predicted branching ratio of less than $10^{-10}$,
is among the best processes to reveal indirect effects of new physics.
The NA62 experiment at CERN SPS is designed to study the $K^+\to\pi^+\nu\bar{\nu}$ decay and to measure its branching ratio using a decay-in-flight technique.
NA62 took data in 2016, 2017 and 2018, reaching the sensitivity of the Standard Model
for the $K^+\to\pi^+\nu\bar{\nu}$ decay by the analysis of the 2016 and 2017 data,
and providing the most precise measurement of the branching ratio to date
by the analysis of the 2018 data.
This measurement is also used to set limits on BR($K^+\to\pi^+X$), where $X$ is a scalar
or pseudo-scalar particle.
The final result of the BR($K^+\to\pi^+\nu\bar{\nu}$) measurement and its interpretation in terms
of the $K^+\to\pi^+ X$ decay from the analysis of the full 2016-2018 data set is presented, and future plans and prospects are reviewed..
2022 - 6 p.
- Published in : PoS DISCRETE2020-2021 (2022) 070
Fulltext: PDF;
In : 7th Symposium on Prospects in the Physics of Discrete Symmetries (DISCRETE 2020-2021), Bergen, Norway, 29 Nov - 3 Dec 2021, pp.070
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Measurement of the very rare $K^+\rightarrow\pi^+\nu\bar{\nu}$ decay
/ Cortina Gil, E
The NA62 experiment reports the branching ratio measurement BR$(K^+ \rightarrow \pi^+ \nu\bar{\nu}) = (10.6^{+4.0}_{-3.4} |_{\rm stat} \pm 0.9_{\rm syst}) \times 10 ^{-11}$ at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016-2018. This provides evidence for the very rare $K^+ \to \pi^+ \nu\bar{\nu}$ decay, observed with a significance of 3.4$\sigma$. [...]
CERN-EP-2021-050.-
Geneva : CERN, 2021 - 22.
Draft (restricted): PDF; Fulltext: PDF;
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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) ; Bryman, Douglas (British Columbia U. ; TRIUMF) ; Numao, Toshio (TRIUMF) ; Velghe, Bob (TRIUMF) ; Wong, Vincent Wai Sum (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, 2024 - 29 p.
Draft (restricted): PDF; Fulltext: CERN-EP-2024-343 - PDF; 2412.12015 - PDF;
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Search for exotic particle at NA62
/ Lollini, Riccardo (INFN, Perugia ; Perugia U.)
/NA62
The NA62 experiment at the CERN SPS is currently taking data to measure the ultra-rare decay $K^+ \rightarrow \pi^+\nu\bar\nu$. Owing to the high beam-energy and a hermetic detector coverage, NA62 also has the opportunity to directly search for a plaethora of long-lived beyond-the Standard Model particles, such as Heavy Neutral Leptons, Axion-like Particles and Dark Photons. [...]
SISSA, 2018 - 6 p.
- Published in : PoS DIS2018 (2018) 088
Fulltext: PDF; External link: PoS server
In : XXVI International Workshop on Deep Inelastic Scattering and Related Subjects, Kobe, Hyogo, Japan, 16 - 20 Apr 2018, pp.088
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