Speaker
Description
The aim of the poster is to demonstrate status of the work in estimation of NA62 [1] experiment sensitivity towards the search for forbidden decay $\pi^{0}\rightarrow3\gamma$ and rare decay $\pi^{0}\rightarrow4\gamma$. Current branching-ratio upper limit is $3.1\times10^{-8}\:(90\%\;\textrm{C.L.})$ for the $\pi^{0}\rightarrow3\gamma$ decay and $2\times10^{-8}\:(90\%\;\textrm{C.L.})$ for $\pi^{0}\rightarrow4\gamma$ decay established in Los Alamos National Laboratory [2].
$K^{+}\rightarrow\pi^{+}\pi^{0}$ decays were used as a source of $\pi^{0}$. Selection criteria for events with 3 or 4 products after $\pi^{0}$ decay in NA62 detector were developed. NA62 detector and all physical processes were modelled with Monte Carlo method using Geant4. Estimation of experiment sensitivity without background events consideration is 1 order better, than current upper limit for $\pi^{0}\rightarrow3\gamma$ and $\pi^{0}\rightarrow4\gamma$ decays. Background processes for both decays were studied. Main contribution in background events is $K^{+}\rightarrow\pi^{+}\pi^{0}, \pi^{0}\rightarrow2\gamma$ decay, when photon interacts with detector, and $e^{+}e^{-}$ pair is created. Comparison of Monte Carlo simulation and experimental data was done. The estimation of number of background events inside signal region was obtained.
Literature:
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Cortina Gil E., et al. The Beam and detector of the NA62 experiment at CERN // JINST 2017. V. 12. P05025
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McDonough J., et al. New searches for the C-noninvariant decay $\pi^{0}\rightarrow3\gamma$ and the rare decay $\pi^{0}\rightarrow4\gamma$// Phys. Rev. D 38(1988), 2121
