Observation of the Decays Λ_{b}^{0}→χ_{c1}pK^{-} and Λ_{b}^{0}→χ_{c2}pK^{-}

Area of Science:

• Particle Physics
• High Energy Physics
• Hadron Spectroscopy

Background:

• The study of heavy baryon decays provides crucial insights into the fundamental forces governing particle interactions.
• Understanding the properties of the Lambda_b0 baryon (Λ_{b}^{0}) is essential for testing theoretical models in quantum chromodynamics.
• Previous measurements have established the decay of Lambda_b0 (Λ_{b}^{0}) into J/ψpK^{-}, serving as a reference channel.

Purpose of the Study:

• To report the first observation of the decays Lambda_b0 (Λ_{b}^{0}) → chi_c1 (χ_{c1}) pK^{-} and Lambda_b0 (Λ_{b}^{0}) → chi_c2 (χ_{c2}) pK^{-}.
• To measure the ratios of branching fractions for these new decay modes relative to the established Lambda_b0 (Λ_{b}^{0}) → J/ψpK^{-} decay.
• To precisely determine the mass of the Lambda_b0 (Λ_{b}^{0}) baryon using the observed decay modes.

Main Methods:

• Analysis of a large dataset collected by the LHCb experiment from proton-proton collisions at 7 and 8 TeV.
• Application of advanced data analysis techniques to identify and reconstruct the final states of the decays.
• Statistical methods to determine the significance of the observations and measure the branching fractions and mass.

Main Results:

• The first observation of Lambda_b0 (Λ_{b}^{0}) → chi_c1 (χ_{c1}) pK^{-} and Lambda_b0 (Λ_{b}^{0}) → chi_c2 (χ_{c2}) pK^{-} decays.
• Measurement of the branching fraction ratios: B(Λ_{b}^{0}→χ_{c1}pK^{-})/B(Λ_{b}^{0}→J/ψpK^{-})=0.242±0.014±0.013±0.009 and B(Λ_{b}^{0}→χ_{c2}pK^{-})/B(Λ_{b}^{0}→J/ψpK^{-})=0.248±0.020±0.014±0.009.
• Measurement of the Lambda_b0 (Λ_{b}^{0}) baryon mass: m_{Λ_{b}^{0}}=5619.44±0.28±0.26 MeV/c^{2}.

Conclusions:

• The observed decays provide new avenues for studying the properties of the Lambda_b0 (Λ_{b}^{0}) baryon.
• The precise measurements contribute to a better understanding of heavy quark dynamics and hadron structure.
• These results enhance the particle physics landscape and offer valuable data for theoretical model comparisons.