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HK: Fachverband Physik der Hadronen und Kerne

HK 31: Hadron Structure and Spectroscopy V

HK 31.5: Talk

Tuesday, March 29, 2022, 17:15–17:30, HK-H8

Pentaquark search in Λ_b⁰→ Λ_c⁺ D^*0 K⁻ decays with missing neutrals — •Mindaugas Sarpis — University of Bonn, Bonn, Germany

Charmonium-pentaquarks, P_c, were observed by LHCb in 2015 and 2019 as resonances in the J/ψ p final state from Λ_b → J/ψ p K⁻ decays. The nature of these resonances is not yet fully understood, but their proximity to baryon-meson thresholds, like Σ_c D^*0, motivate ‘molecular’ pentaquark models. Several phenomenological studies predict large branching fractions for the decay of P_c → Λ_c⁺ D^*0. The ratio of branching fraction of the exclusive Λ_b⁰→ Λ_c⁺ D^*0 K⁻ channel with respect to Λ_b⁰→ Λ_c⁺D_s was measured to be 0.569 ± 0.015 ± 0.017 ± 0.016, where the first uncertainty is statistical, the second systematic, and the third due to the uncertainty on the D branching fractions. Due to the low reconstruction efficiency of π⁰ or γ candidates in the decay D^*0 → D⁰ π⁰/γ, a kinematic over-constraint method, Extended Cone Closure, is employed to reconstruct the four-momentum of the D^*0 and be able to study the Dalitz plot of Λ_c⁺D^*0−D^*0K⁻. A model independent approach using Legendre moments analysis and the limit setting procedure for the upper limit on P_c yield is presented.