### Chen–Ruan Cohomology of ${\mathcal{M}}_{1,n}$ and ${\overline{\mathcal{M}}}_{1,n}$

In this work we compute the Chen–Ruan cohomology of the moduli spaces of smooth and stable $n$-pointed curves of genus $1$. In the first part of the paper we study and describe stack theoretically the twisted sectors of ${\mathcal{M}}_{1,n}$ and ${\overline{\mathcal{M}}}_{1,n}$. In the second part, we study the orbifold intersection theory of ${\overline{\mathcal{M}}}_{1,n}$. We suggest a definition for an orbifold tautological ring in genus $1$, which is a subring of both the Chen–Ruan cohomology and of the stringy Chow ring.