| 20 |  | i.e., variable factorization and renormalization scales,set to the central mT^2 scale after kT-clustering of the event. | 
          
            | 21 |  | For a single heavy particle, this corresponds to the M^2+pT^2, | 
          
            | 22 |  | for pair of heavy particles it is the geometric mean of M^2+pT^2 for each particle, | 
          
            | 23 |  | for massless particles it is the pT^2 of the last pair after clustering. | 
          
            | 24 |  | If the last clustering is a t-channel colorless exchange (as, e.g., in WBF),  the two fact. scales are set to the last mT^2 values on either side. | 
          
            |  | 20 | i.e., variable factorization and renormalization scales,set to the central mT^2^ scale after kT-clustering of the event. | 
          
            |  | 21 | For a single heavy particle, this corresponds to the M^2^+pT^2^, | 
          
            |  | 22 | for pair of heavy particles it is the geometric mean of M^2^+pT^2^ for each particle, | 
          
            |  | 23 | for massless particles it is the pT^2^ of the last pair after clustering. | 
          
            |  | 24 | If the last clustering is a t-channel colorless exchange (as, e.g., in WBF),  the two fact. scales are set to the last mT^2^ values on either side. | 
          
            |  | 25 |  |