Evaluate real and imaginary part of $\Gamma\left(\frac{2}{3},-\frac{1}{3}\right)$

cauchy-principal-valuecomplex numberscomplex-analysisdefinite integralsgamma function

I calculated the principal value of the following integral:
$$PV\int_{0}^{\infty}\frac{t^{\frac{1}{3}}e^{-t}}{1-3t}dt=\left(\frac{\Im\left[\left(-1\right)^{\frac{5}{6}}\Gamma\left(\frac{2}{3},-\frac{1}{3}\right)\right]}{\sqrt[3]{3e}}-1\right)\Gamma\left(\frac{4}{3}\right)\approx -0.225197$$
I know that
$$(-1)^{5/6}=-\frac{\sqrt{3}}{2}+\frac{i}{2}$$
But I don't know how to express the real and the imaginary part of $\Gamma\left(\frac{2}{3},-\frac{1}{3}\right)$
$$\Gamma\left(\frac{2}{3},-\frac{1}{3}\right)=\int_{-\frac{1}{3}}^{\infty}e^{-t}t^{2/3-1}\mathrm{d}t\approx 1.7682-0.717204 i$$


Edit
A resolution like this would be fine too
$$\Gamma\left(\frac{2}{3},-\frac{1}{3}\right)=\underbrace{\int_{a_1}^{b_1}f_1(t)\mathrm{d}t}_{\in\mathbb{R}}+i \underbrace{\int_{a_2}^{b_2}f_2(t)\mathrm{d}t}_{\in\mathbb{R}}$$

Best Answer

Can be converted to hypegeometric ... \begin{align} \int_0^\infty \!{{{\rm e}^{-t}}{\frac {1}{\sqrt [3]{t}}}}\,{\rm d}t &=\Gamma\left(\frac23\right) \qquad\text{[real]} \\ \int_{-1/3}^0 \!{{{\rm e}^{-t}}{\frac {1}{\sqrt [3]{t}}}}\,{\rm d}t &= -{\frac { \left( i{3}^{{5/6}}-\sqrt [3]{3} \right) {{\rm e}^{{ 1/3}}}}{20\, }\left( {\mbox{$_1$F$_1$}(1;\,{\frac{8}{3}};\,-{\frac{1}{3}})}-5 \right) } \\&= {\frac { \left(\sqrt [3]{3} \right) {{\rm e}^{{ 1/3}}}}{20\, }\left( {\mbox{$_1$F$_1$}(1;\,{\frac{8}{3}};\,-{\frac{1}{3}})}-5 \right) } \qquad\text{[real]} \\&\qquad - i{\frac { \left( {3}^{{5/6}} \right) {{\rm e}^{{ 1/3}}}}{20\, }\left( {\mbox{$_1$F$_1$}(1;\,{\frac{8}{3}};\,-{\frac{1}{3}})}-5 \right) } \qquad\text{[purely imaginary]} \end{align}

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