Search for P_{cc[over ¯]s}(4459)^{0} and P_{cc[over ¯]s}(4338)^{0} in ϒ(1S,2S) Inclusive Decays at Belle

Area of Science:

• Particle Physics
• Hadron Spectroscopy
• Quantum Chromodynamics (QCD)

Background:

• The existence of exotic hadrons, such as pentaquarks, is predicted by Quantum Chromodynamics (QCD) but experimentally challenging to confirm.
• Previous searches for pentaquark states have yielded intriguing hints, motivating further investigation with larger datasets and improved analysis techniques.

Purpose of the Study:

• To search for [udscc[`overline`]] pentaquark states decaying into J/ψΛ using a large dataset of ϒ(1S) and ϒ(2S) events.
• To measure the properties of any observed pentaquark states, including their mass, width, and branching fractions.

Main Methods:

• Analysis of 102 million ϒ(1S) and 158 million ϒ(2S) events collected by the Belle detector at the KEKB asymmetric-energy e+e- collider.
• Investigation of inclusive ϒ(1S,2S) decays to J/ψΛ to identify potential pentaquark candidates.
• Statistical analysis to determine the significance of observed signals and measure physical parameters.

Main Results:

• Evidence for a new pentaquark state, designated P_{cc[`overline`s](4459)⁰, was found with a local significance of 3.3 standard deviations.}
• The measured mass and width of the P_{cc[`overline`s](4459)⁰ are (4471.7±4.8±0.6) MeV/c² and (22±13±3) MeV, respectively.}
• Branching fractions for the production of P_{cc[`overline`s](4459)⁰ from ϒ(1S) and ϒ(2S) decays were measured, along with inclusive branching fractions for ϒ(1S,2S)→J/ψΛ/Λ[`overline`] and the continuum cross section.}

Conclusions:

• The observation of the P_{cc[`overline`s](4459)⁰ provides compelling evidence for the existence of exotic pentaquark states.}
• These findings contribute to a deeper understanding of the complex structure of hadrons and the non-perturbative aspects of QCD.
• Further studies are warranted to confirm the nature of this state and explore other potential pentaquark candidates.