One-loop superstring six-point amplitudes and anomalies in pure spinor superspace

Understand

We present the massless six-point one-loop amplitudes in the open and closed superstring using BRST cohomology arguments from the pure spinor formalism.

• The hexagon gauge anomaly is traced back to a class of kinematic factors in pure spinor superspace which were recently introduced as BRST pseudo-invariants.
• This complements previous work where BRST invariance arguments were used to derive the non-anomalous part of the amplitude.
• The associated worldsheet functions are non-singular and demonstrated to yield total derivatives on moduli space upon gauge variation.