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Volume 332 - XIV International Conference on Heavy Quarks and Leptons (HQL2018) - Kaon Physics
Measurement of $\Gamma(K_{e2})/\Gamma(K_{\mu2})$ ratio using stopped positive kaons at J-PARC
S. Shimizu* on behalf of the JPARC-E36 Collaboration
*corresponding author
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Pre-published on: 2018 December 05
Published on: 2018 December 11
The J-PARC E36 experiment is aiming at searching for the lepton universality violation by precisely measuring the ratio of the branching
ratio of the $K^+ \rightarrow e^+ \nu$ ($K_{e2}$) and $K^+ \rightarrow \mu^+\nu$ ($K_{\mu 2}$) decays.he E36 experiment was performed at J-PARC employing a stopped $K^+$ beam in conjunction with a 12-sector iron-core superconducting toroidal spectrometer. Charged particle momentum was calculated by reconstructing the tracks in the spectrometer. Particle discrimination between $e^+$ and $\mu^+$ was carried out using an aerogel Cherenkov counters and a lead-glass Cherenkov counter, as well as by measuring the time-of-flight between TOF counters. The peak structure due to the $K_{e2}$ decays was successfully observed in the $e^+$ momentum spectrum. The structure-dependent radiative $K^+ \rightarrow e^+ \nu
\gamma$ ($K_{e2 \gamma}$) events can be selected by requiring one photon hit in the CsI(Tl) calorimeter. The experimental spectra were reproduced by the Monte Carlo simulation, which indicates a correctunderstanding of the experimental conditions.
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