Rare meson decays are among the most sensitive probes of both heavy and light new physics. Among them, new physics searches using kaons benefit from their small total decay widths and the ...availability of very large datasets. On the other hand, useful complementary information is provided by hyperon decay measurements. Here, we summarize the relevant phenomenological models and the status of the searches in a comprehensive list of kaon and hyperon decay channels. We identify new search strategies for under-explored signatures, and demonstrate that the improved sensitivities from current and next-generation experiments could lead to a qualitative leap in the exploration of light dark sectors.
Development of the kaon tagging system for the NA62 experiment at CERN Goudzovski, Evgueni; Krivda, Marian; Lazzeroni, Cristina ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2015, Letnik:
801
Journal Article
Recenzirano
The NA62 experiment at CERN aims to make a precision measurement of the ultra-rare decay K+→π+νν¯, and relies on a differential Cherenkov detector (KTAG) to identify charged kaons at an average rate ...of 50MHz in a 750MHz unseparated hadron beam. The experimental sensitivity of NA62 to K-decay branching ratios (BR) of 10−11 requires a time resolution for the KTAG of better than 100ps, an efficiency better than 95% and a contamination of the kaon sample that is smaller than 10−4. A prototype version of the detector was tested in 2012, during the first NA62 technical run, in which the required resolution of 100ps was achieved and the necessary functionality of the light collection system and electronics was demonstrated.
A search for the Lepton Number Violating decay \(K\)\(±\) → \(π\)\(∓\)\(μ\)\(±\)\(μ\)\(±\) has been performed using the data collected by the NA48/2 experiment in 2003 and 2004. The signal event ...selection, the background rejection, the evaluation of the muon identification efficiency and the statistical methods used for the data interpretation are presented. Based on 1.8 x 10\(1\)\(1\) kaon decays in the fiducial volume and using several models for the signal, upper limits for the branching ratio \(B\)(\(K\)\(±\) → \(π\)\(∓\)\(μ\)\(±\)\(μ\)\(±\)) of the order of 10\(-\)\(1\)\(0\) have been obtained for 90%, 95% and 99% confidence levels, improving the previous best limit of one order of magnitude. The Cherenkov differential counter used for kaon identification in the NA62 experiment, equipped with approximately 30% of the photo-detectors, was installed and tested during a Technical Run in 2012. The counter's ability of distinguishing between kaons and pions has been validated via pressure scan procedure. The data collected have been used for evaluating the kaon efficiency and time resolution. The extrapolation to the full-sized detector has been also estimated.
The NA48/2 and NA62-\(R_K\) experiments at CERN collected large samples of charged kaon decays in 2003--2004 and 2007, respectively. These samples, collected with different trigger conditions, allow ...to search for both short and long-living heavy neutrinos produced in \(K^{\pm}\to\mu^{\pm}N_4\) decays. The results of these complementary searches are presented in this letter. In the absence of observed signal, the limits obtained on \(\mathcal{B}(K^{\pm}\to\pi^{\mp}\mu^{\pm}\mu^{\pm})\), \(\mathcal{B}(K^{\pm}\to \mu^{\pm} N_4)\mathcal{B}(N_4\to \pi\mu)\), \(\mathcal{B}(K^{+}\to\mu^{+}N_4)\) and on the mixing matrix element \(|U_{\mu4}|^2\) are reported.
The NA48/2 experiment at CERN collected a large sample of charged kaon decays
into final states with multiple charged particles in 2003--2004. A new upper
limit on the rate of the lepton number ...violating decay
$K^{\pm}\to\pi^{\mp}\mu^{\pm}\mu^{\pm}$ obtained from this sample is reported:
$\mathcal{B}(K^{\pm}\to\pi^{\mp}\mu^{\pm}\mu^{\pm})<8.6 \times 10^{-11}$ at
90\% CL. Searches for two-body resonances in the $K^{\pm}\to\pi\mu\mu$ decays
(including heavy neutral leptons~$N_4$ and inflatons~$\chi$) in the accessible
range of masses and lifetimes are also presented. In the absence of a signal,
upper limits are set on the products of branching
ratios~$\mathcal{B}(K^{\pm}\to\mu^{\pm}N_4)\mathcal{B}(N_4\to\pi\mu)$ and
$\mathcal{B}(K^{\pm}\to\pi^{\pm}\chi)\mathcal{B}(\chi\to\mu^+\mu^-)$ as
functions of the resonance mass and lifetime. These limits are in the
$10^{-10}-10^{-9}$ range for resonance lifetimes below 100~ps.
The NA48/2 experiment at CERN collected a large sample of charged kaon decays
into final states with multiple charged particles in 2003--2004. A new upper
limit on the rate of the lepton number ...violating decay $K^{\pm} \to \pi^{\mp}
\mu^{\pm} \mu^{\pm}$ obtained from this sample is reported:
$\mathcal{B}(K^{\pm} \to \pi^{\mp} \mu^{\pm} \mu^{\pm})<8.6 \times 10^{-11}$ at
90\% CL. Searches for two-body resonances in the $K^{\pm} \to \pi\mu\mu$ decays
(including heavy neutral leptons~$N_4$ and inflatons~$\chi$) in the accessible
range of masses and lifetimes are also presented. In the absence of a signal,
upper limits are set on the products of branching ratios~$\mathcal{B}(K^{\pm}
\to \mu^{\pm} N_{4})\mathcal{B}(N_{4} \to \pi^{\mp}\mu^{\pm})$ and
$\mathcal{B}(K^{\pm} \to \pi^{\pm} \chi)\mathcal{B}(\chi \to \mu^{+}\mu^{-})$
as functions of the resonance mass and lifetime. These limits are in the
$10^{-10}-10^{-9}$ range for resonance lifetimes below 100~ps.
Rare $B$, $D$ and $K$ decays provide interesting probes of the Standard Model
(SM), with a potential sensitivity to New Physics (NP) higher than other, more
common, decays. Their experimental ...measurement is challenging, and their
theoretical interpretation requires a precise knowledge of QCD at low energies,
in the non-perturbative (hadronic) regime. The various $b$, $c$, $s$ decays
provide different types of tests of the Standard Model, which can be performed
in different experimental settings and which may exhibit correlated deviations
in models of New Physics.
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