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

1. Jul 2, 2015

### 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...

2. Jul 3, 2015

### Staff: Mentor

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.

3. Jul 3, 2015

### ChrisVer

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

4. Jul 4, 2015

### Staff: Mentor

Weighting by momentum gives better results.