First Observation of $\Lambda {\pi }^{+}$ and $\Lambda {\pi }^{-}$ Signals near the $\bar{K}N(I=1)$ Mass Threshold in ${\Lambda }_c^{+}\to \Lambda {\pi }^{+}{\pi }^{+}{\pi }^{-}$ Decay

Abstract

Using the data sample of 980 fb${}^{-1}$ collected with the Belle detector operating at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider, we present the results of an investigation of the $\Lambda {\pi }^{+}$ and $\Lambda {\pi }^{-}$ invariant mass distributions looking for substructure in the decay ${\Lambda }_c^{+}\to \Lambda {\pi }^{+}{\pi }^{+}{\pi }^{-}$. We find a significant signal in each mass dis\ tribution. When interpreted as resonances, we find for the $\Lambda {\pi }^{+}$ ($\Lambda {\pi }^{-}$) combination a mass of $1434.3\pm 0.6(\mathrm{stat})\pm 0.9(\mathrm{syst})$ MeV/$c^2$ [$1438.5\pm 0.9(\mathrm{stat})\pm 2.5(\mathrm{syst})$ MeV/$c^2$], an intrinsic width of $11.5\pm 2.8(\mathrm{stat})\pm 5.3(\mathrm{syst})$ MeV/$c^2$ [$33.0\pm 7.5(\mathrm{stat})\pm 23.6(\mathrm{syst})$ MeV/$c^2$] with a significance of 7.5$\sigma$ (6.2$\sigma$). As these two signals are very close to the $\bar{K}N$ threshold, we also investigate the possibility of a $\bar{K}N$ cusp, and find that \ we cannot discriminate between these two interpretations due to the limited size of the data sample.

References in corpus (2)

• K^- p scattering length from scattering experiments
• Lattice QCD Evidence that the Lambda(1405) Resonance is an Antikaon-Nucleon Molecule

Cited by in corpus (9)

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• The odd-parity strange baryons $\Sigma ({\frac{1}{2}}^{-})$ below 1.8 GeV with Hamiltonian effective field theory
• Role of ${\Sigma }^{\ast }(1/2^{-})$ baryons in ${\Lambda }_c\to \Lambda {\pi }^{+}{\pi }^{+}{\pi }^{-}$ decay
• Low-energy $N\varphi$ scattering from a pole-enhanced triangle diagram
• Search for the low-lying excited baryon ${\Sigma }^{\ast }(1/2^{-})$ through process ${\Lambda }_c^{+}\to \Lambda K^0{\pi }^{+}$
• Finite-temperature effects on the threshold cusps in $\pi \pi$ and $D{\bar{D}}^{\ast }$ scatterings from relativistic heavy-ion collisions
• Low-lying $\Lambda$ and $\Sigma$ resonances studied with the forward $K^{\ast }$ productions off the proton induced by a high-momentum $\pi$ beam