Observation of a New Excited $Σ$ State in $ψ(3686)\to\bar{p}K^+Σ^0+c.c.$

Abstract

Using a data sample of $(2712.4\pm14.3)\times10^6\ ψ(3686)$ events collected with the BESIII detector, a partial-wave analysis of $ψ(3686)\to\bar{p}K^+Σ^0+c.c.$ is performed. A new excited $Σ$ baryon state is observed with a statistical significance of $11.9σ$, and the mass and width are measured as $(2334.7\pm7.9\pm16.0)\;\mathrm{MeV}/c^2$ and $(206.3\pm9.5\pm18.4)\;\mathrm{MeV}$, respectively. The spin-parity of the new state is favored to be $3/2^-$, and the branching fraction of $ψ(3686)\to\barΣ(2330)^0Σ^0+c.c.$ is determined to be $(4.47\pm0.58\pm1.52)\times10^{-6}$. In addition, the branching fraction of $ψ(3686)\to\bar{p}K^+Σ^0+c.c.$ is determined to be either $(2.44\pm0.20\pm0.08)\times10^{-5}$ or $(1.73\pm0.29\pm0.06)\times10^{-5}$ by considering two solutions. The first uncertainties are statistical and the second systematic.

Figures (3)

• Figure 1: Fit to the $M_{\gamma\Lambda}$ distribution. Dots with error bars are data; the brown solid curve shows the total fit; the red dashed curve is the signal; the blue dashed curve is the non-peaking background; the yellow dashed curve is the continuum background.
• Figure 2: Dalitz plots of $M^2_{\bar{p}K^+}$ versus $M^2_{K^+\Sigma^0}$ of (a) data and (b) the normalized PWA fit result, and the red curves correspond the kinematic boundary.
• Figure 3: Distributions of $M_{\bar{p}K^+}$, $M_{\bar{p}\Sigma^0}$, $M_{K^+\Sigma^0}$, $\cos_{\bar{p}K^+}(\theta_{\bar{p}})$, $\cos_{\bar{p}\Sigma^0}(\theta_{\Sigma^0})$ and $\cos_{K^+\Sigma^0}(\theta_{K^+})$.