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Register a new userLong-lived neutral-kaon flux measurement for the KOTO experiment
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Takahiko Masuda Dr.
Publication date
2015
fields
Physics
and research's language is
English
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The KOTO ($K^0$ at Tokai) experiment aims to observe the CP-violating rare decay $K_L rightarrow pi^0 u bar{ u}$ by using a long-lived neutral-kaon beam produced by the 30 GeV proton beam at the Japan Proton Accelerator Research Complex. The $K_L$ flux is an essential parameter for the measurement of the branching fraction. Three $K_L$ neutral decay modes, $K_L rightarrow 3pi^0$, $K_L rightarrow 2pi^0$, and $K_L rightarrow 2gamma$ were used to measure the $K_L$ flux in the beam line in the 2013 KOTO engineering run. A Monte Carlo simulation was used to estimate the detector acceptance for these decays. Agreement was found between the simulation model and the experimental data, and the remaining systematic uncertainty was estimated at the 1.4% level. The $K_L$ flux was measured as $(4.183 pm 0.017_{mathrm{stat.}} pm 0.059_{mathrm{sys.}}) times 10^7$ $K_L$ per $2times 10^{14}$ protons on a 66-mm-long Au target.
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The NA62 experiment at CERN aims to make a precision measurement of the ultra-rare decay $K^{+} rightarrow pi^{+} uoverline{ u}$, and relies on a differential Cherenkov detector (KTAG) to identify charged kaons at an average rate of 50 MHz in a 750 MHz 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 100 ps, 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 100 ps was achieved and the necessary functionality of the light collection system and electronics was demonstrated.
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