First measurement of the Λc+ → pη′ decay

We present the first measurement of the branching fraction of the singly Cabibbo-suppressed (SCS) decay Λc+→ pη′ with η′ → ηπ⁺π⁻, using a data sample corresponding to an integrated luminosity of 981 fb⁻¹, collected by the Belle detector at the KEKB e⁺e⁻ asymmetric-energy collider. A significant Λc+→ pη′ signal is observed for the first time with a signal significance of 5.4σ. The relative branching fraction with respect to the normalization mode Λc+→ pK⁻π⁺ is measured to beB(Λc+→pη′)B(Λc+→pK−π+)=(7.54±1.32±0.73)×10−3, where the uncertainties are statistical and systematic, respectively. Using the world-average value of B(Λc+→pK−π+) = (6.28 ± 0.32) × 10⁻², we obtainB(Λc+→pη′)=(4.73±0.82±0.46±0.24)×10−4, where the uncertainties are statistical, systematic, and from B(Λc+→pK−π+), respectively. [Figure not available: see fulltext.]