Nature of χ_{c1}(3872) and T_{cc}^{+}(3875)

Area of Science:

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

Background:

• The discovery of the chi_c1(3872) state two decades ago initiated research into exotic XYZ states beyond the conventional quark model.
• These exotic states, including tetraquarks and pentaquarks, offer insights into the fundamental strong force and new forms of matter.
• The precise nature of states like chi_c1(3872) and T_cc+(3875) remains a subject of extensive discussion.

Purpose of the Study:

• To determine the composition of the chi_c1(3872) and T_cc+(3875) exotic states using Quantum Chromodynamics (QCD).
• To apply the Born-Oppenheimer effective field theory (BOEFT) to elucidate the nature of these unusual hadron states.
• To extend the application of BOEFT to predict properties of other exotic states, particularly in the bottomonium sector.

Main Methods:

• Utilized the Born-Oppenheimer effective field theory (BOEFT) framework.
• Applied Quantum Chromodynamics (QCD) principles to analyze the structure of heavy quark states.
• Performed theoretical calculations to describe the main features of the studied XYZ states.

Main Results:

• Successfully described the main characteristics of the chi_c1(3872) and T_cc+(3875) states.
• Provided a QCD-based explanation for the composition of these exotic hadrons.
• Generated predictions for states within the bottomonium sector.

Conclusions:

• The Born-Oppenheimer effective field theory (BOEFT) effectively clarifies the composition of exotic XYZ states like chi_c1(3872) and T_cc+(3875).
• This approach provides a pathway for systematic investigations of all XYZ states using BOEFT.
• The study opens new avenues for understanding novel forms of matter governed by the strong force.