Two-loop five-point all-plus helicity Yang-Mills amplitude

We recompute the recently derived two-loop five-point all-plus Yang-Mills amplitude using unitarity and recursion. Recursion requires augmented recursion to determine the subleading pole. Using these methods, the simplicity of this amplitude is understood.

Figure 1

Contributions to the two-loop amplitudes involving an all-plus loop (indicated by the solid disc).

Figure 2

The labeling and internal helicities of the quadruple cut.

Figure 3

The origin of the double poles in $s_{de}$. The diagram has an explicit pole and an additional pole can arise from the triangle integral.

Figure 4

The nonfactorizing contribution to the pole. We must also include the case with the helicities on $\alpha$ and $\beta$ reversed.

Figure 5

Sources of $s_{\alpha \beta }$ poles in ${\tau }^1$.

Figure 6

Sources of $s_{\alpha \beta }$ poles in contributions from ${\tau }^0$.