Exploring the $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\Lambda }_c^{-}$ cross sections

Abstract

A simultaneous fit is performed to the $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\Lambda }_c^{-}$ cross section data measured by Belle and BESIII from threshold up to 5.4 GeV. In order to accommodate both the BESIII measurement near threshold and the Belle observation of a resonance $Y(4630)$, we build a composite PDF with a Breit-Wigner resonance and a continuum contribution to model the full cross section line shape of $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\Lambda }_c^{-}$. The fit gives a mass of $M=[4636.1_{-7.2}^{+9.8}($stat$)\pm 8.0($syst$)]$~MeV/$c^2$, a width of ${\Gamma }_{\mathrm{tot}}=[34.5_{-16.2}^{+21.0}($stat$)\pm 5.6($syst$)]$~MeV, and ${\Gamma }_{e^{+}{e}^{-}}\mathcal{B}[Y(4630)\to {\Lambda }_c^{+}{\Lambda }_c^{-}]=[18.3_{-6.1}^{+8.8}($stat$)\pm 1.1($syst$)]$~eV/$c^2$ for the resonance. The width of $Y(4630)$ from our study is narrower than the previous Belle fit. The mass and width of $Y(4630)$ also show good agreement with a vector resonance $Y(4626)$ recently observed in $D_s^{+}{D}_{s1}(2536{)}^{-}$ by Belle.

Comments: 9 pages, 4 figures