What does "momentum-weighted 'variable' " mean?

[ChrisVer]

It's pretty clear by the title... what does it mean to say something like (check http://arxiv.org/pdf/hep-ex/0606027v1.pdf pg5 ends of left column) "a momentum-weighted charge of the decay products of the second b..." ?
I don't understand why someone would use momentum-weighted variables and what are they...

 

[mfb]

They take momenta as weights for adding the charges, $\sum p_i q_i$ (maybe divided by the sum of momenta, and probably with transverse momentum instead of momentum but literally it would be momentum). This increases the importance of high-momentum tracks, which are generally easier to reconstruct (and more likely to come from the decay) and also more likely to be closely related to the decaying particle.

 

[ChrisVer]

so they think that for some reason the variable "measurement" is correlated to the momentum?

 

[mfb]

Weighting by momentum gives better results.