Kernbremsstrahlung of a muon in the EMC section produces a high energy gamma which showers in the EMC. This can result in a shower very similar to that of a final state positron of a genuine positron-proton collision event.
In order to avoid misidentification MUFFIN tries to find a final state positron prior to execution if the value of the event is compatible with an NC event: If and then MUFFIN runs the SINISTRA positron finder [40]. If a positron has been found by that finder and if there is a condensate that contains nothing but those cells then this condensate is tagged. Should a muon candidate be found that contains this condensate the candidate will be tagged too, this tag can then be used in the muon classification (see section 6.7.3) to reject the candidate.