Probing double hadron resonance by the complex-momentum-representation method

Resonances are ubiquitous phenomena in nature, and physicists have developed many methods to explore resonant states. Of particular note is the complex-momentum-representation (CMR) method, which has been developed and widely used in the study of resonant states in atomic, molecular, and nuclear physics. Here, for the first time, we have developed this novel method to study hadron resonant states. The CMR method is applied to probe the bound and resonant states for the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msub><a:mi mathvariant="normal">Λ</a:mi><a:mi>c</a:mi></a:msub><a:mi>D</a:mi><a:mo stretchy="false">(</a:mo><a:mover accent="true"><a:mi>D</a:mi><a:mo stretchy="false">¯</a:mo></a:mover><a:mo stretchy="false">)</a:mo></a:math> and <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:msub><h:mi mathvariant="normal">Λ</h:mi><h:mi>c</h:mi></h:msub><h:msub><h:mi mathvariant="normal">Λ</h:mi><h:mi>c</h:mi></h:msub><h:mo stretchy="false">(</h:mo><h:msub><h:mover accent="true"><h:mi mathvariant="normal">Λ</h:mi><h:mo stretchy="false">¯</h:mo></h:mover><h:mi>c</h:mi></h:msub><h:mo stretchy="false">)</h:mo></h:math> systems, in which the resonant states are exposed clearly in the complex momentum plane and the resonance parameters can be determined precisely without imposing unphysical parameters. The results show that the CMR method has achieved higher accuracy than other widely used methods. This method is not only very effective for narrow resonances, but also can be reliably applied to broad resonances.