U⁡(a,z)=ⅇ14⁢z2ⅈ⁢2⁢π⁢∫c-ⅈ⁢∞c+ⅈ⁢∞ⅇ-z⁢t+12⁢t2⁢t-a-12⁢ⅆ⁡t,