Updated SM predictions yield Br(η→e⁺e⁻)=5.37(4)(2)[4]×10⁻⁹, Br(η→μ⁺μ⁻)=4.54(4)(2)[4]×10⁻⁶, Br(η'→e⁺e⁻)=1.80(2)(3)[3]×10⁻¹⁰, and Br(η'→μ⁺μ⁻)=1.22(2)(2)[3]×10⁻⁷, with a mild 1.6σ tension in the η→μ⁺μ⁻ channel.
Rare decay $\pi^{0}\to e^+ e^-$ constraints on the light CP-odd Higgs in NMSSM
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abstract
We constrain the light CP-odd Higgs $A_{1}^{0}$ in NMSSM via the rare decay $\pi^{0}\to e^{+}e^{-}$. It is shown that the possible $3\sigma$ discrepancy between theoretical predictions and the recent KTeV measurement of ${\cal B}({\pi}^{0}\to e^+ e^-)$ cannot be resolved when the constraints from $\Upsilon\to\gamma A_1^0$, $a_{\mu}$ and $\pi^{0}\to \gamma \gamma$ are combined. Furthermore, the combined constraints also exclude the scenario involving $m_{A_1^0}=214.3$ MeV, which is invoked to explain the anomaly in the $\Sigma^{+}\to p \mu^{+}\mu^{-}$ decay found by the HyperCP Collaboration.
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Improved Standard-Model predictions for $\eta^{(\prime)}\to \ell^+ \ell^-$
Updated SM predictions yield Br(η→e⁺e⁻)=5.37(4)(2)[4]×10⁻⁹, Br(η→μ⁺μ⁻)=4.54(4)(2)[4]×10⁻⁶, Br(η'→e⁺e⁻)=1.80(2)(3)[3]×10⁻¹⁰, and Br(η'→μ⁺μ⁻)=1.22(2)(2)[3]×10⁻⁷, with a mild 1.6σ tension in the η→μ⁺μ⁻ channel.