Evidence of Two Resonant Structures in e^{+}e^{-}→π^{+}π^{-}h_{c}.

Area of Science:

• High Energy Physics
• Particle Physics
• Quantum Chromodynamics

Background:

• Understanding the complex spectrum of charmonium states is crucial for testing quantum chromodynamics.
• Previous studies of e^{+}e^{-}→π^{+}π^{-}J/ψ and e^{+}e^{-}→π^{+}π^{-}ψ(2S) revealed specific resonance structures.

Purpose of the Study:

• To measure the cross sections of the e^{+}e^{-}→π^{+}π^{-}h_{c} reaction.
• To search for and characterize new resonance states in this process.
• To compare the observed line shape with previously known charmonium states.

Main Methods:

• Data collection using the BESIII detector at the Beijing Electron Positron Collider.
• Analysis of e^{+}e^{-} collision data within a center-of-mass energy range of 3.896 to 4.600 GeV.
• Fitting the cross section data with a coherent sum of two Breit-Wigner functions to determine resonance parameters.

Main Results:

• The cross sections for e^{+}e^{-}→π^{+}π^{-}h_{c} were measured and found to be comparable in magnitude to those of e^{+}e^{-}→π^{+}π^{-}J/ψ and e^{+}e^{-}→π^{+}π^{-}ψ(2S).
• Two distinct resonance structures, designated Y(4220) and Y(4390), were observed in the e^{+}e^{-}→π^{+}π^{-}h_{c} cross sections.
• Precise mass and width measurements were obtained for Y(4220) and Y(4390), with statistical significances of 10σ for each structure under a single-structure assumption.

Conclusions:

• The observed resonance structures Y(4220) and Y(4390) in the e^{+}e^{-}→π^{+}π^{-}h_{c} channel are distinct from those seen in related processes.
• These findings contribute to the ongoing exploration of exotic charmonium states and provide new data for theoretical models.
• The precise measurements of Y(4220) and Y(4390) properties will aid in their classification and understanding within the broader context of heavy quarkonium physics.