Based on $(10087 \pm 44)\times10^{6}$ $J/\psi$ events collected by the BESIII detector at the center-of-mass energy $\sqrt{s}=3.097~\mathrm{GeV}$, the first absolute measurement of the branching fractions for the decays $\Sigma^+ \to p\pi^0$ and $\Sigma^+ \to n\pi^+$ is performed. The branching fractions are determined to be $$\mathcal{B}(\Sigma^+ \to p\pi^0) = (49.79 \pm 0.06\,(\mathrm{stat}) \pm 0.22\,(\mathrm{syst}))\%,$$ and $$\mathcal{B}(\Sigma^+ \to n\pi^+) = (49.87 \pm 0.05\,(\mathrm{stat}) \pm 0.29\,(\mathrm{syst}))\%,$$ where the first uncertainties are statistical and the second are systematic. Our results show significant deviations from the Particle Data Group values for both decays, with differences of $4.4\sigma$ for $\Sigma^+ \to p\pi^0$ and $3.4\sigma$ for $\Sigma^+ \to n\pi^+$. These measurements will play an important role in precision studies of the decay properties of strange, charmed, and beauty baryons with a $\Sigma^+$ in the final state. Furthermore, the $\Delta I = 1/2$ rule is tested in nonleptonic $\Sigma$ decays. The observed results deviate from zero by more than $5\sigma$, indicating the presence of a $\Delta I = 3/2$ transition amplitude in $\Sigma$ hyperon decays.
First measurement of the absolute branching fractions of Σ+ nonleptonic decays and test of the Δ𝐼 =1/2 rule
Garzia, I.;Melendi, F. M.;
2026
Abstract
Based on $(10087 \pm 44)\times10^{6}$ $J/\psi$ events collected by the BESIII detector at the center-of-mass energy $\sqrt{s}=3.097~\mathrm{GeV}$, the first absolute measurement of the branching fractions for the decays $\Sigma^+ \to p\pi^0$ and $\Sigma^+ \to n\pi^+$ is performed. The branching fractions are determined to be $$\mathcal{B}(\Sigma^+ \to p\pi^0) = (49.79 \pm 0.06\,(\mathrm{stat}) \pm 0.22\,(\mathrm{syst}))\%,$$ and $$\mathcal{B}(\Sigma^+ \to n\pi^+) = (49.87 \pm 0.05\,(\mathrm{stat}) \pm 0.29\,(\mathrm{syst}))\%,$$ where the first uncertainties are statistical and the second are systematic. Our results show significant deviations from the Particle Data Group values for both decays, with differences of $4.4\sigma$ for $\Sigma^+ \to p\pi^0$ and $3.4\sigma$ for $\Sigma^+ \to n\pi^+$. These measurements will play an important role in precision studies of the decay properties of strange, charmed, and beauty baryons with a $\Sigma^+$ in the final state. Furthermore, the $\Delta I = 1/2$ rule is tested in nonleptonic $\Sigma$ decays. The observed results deviate from zero by more than $5\sigma$, indicating the presence of a $\Delta I = 3/2$ transition amplitude in $\Sigma$ hyperon decays.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
