The unequal mass sunrise integral expressed through iterated integrals on ${\overline{\mathcal{M}}}_{1,3}$

Abstract

We solve the two-loop sunrise integral with unequal masses systematically to all orders in the dimensional regularisation parameter $\epsilon$. In order to do so, we transform the system of differential equations for the master integrals to an $\epsilon$-form. The sunrise integral with unequal masses depends on three kinematical variables. We perform a change of variables to standard coordinates on the moduli space ${\mathcal{M}}_{1,3}$ of a genus one Riemann surface with three marked points. This gives us the solution as iterated integrals on ${\overline{\mathcal{M}}}_{1,3}$. On the hypersurface $\tau =\text{mbox}const$ our result reduces to elliptic polylogarithms. In the equal mass case our result reduces to iterated integrals of modular forms.

Comments: 34 pages, v2: version to be published