# A (Event generation) What information do you get...

1. Jun 7, 2016

### ChrisVer

What information do you get by reading that some sample production (like the W/Z for Powheg) is normalized to the NNLO cross sections?

2. Jun 9, 2016

### ofirg

The Meaning on that statement is that the total number of events is normalized to the calculated NNLO inclusive cross section.

The production itself is done at a lower order (LO or NLO), so the shapes of all the distrubutions reflect these lower orders.

But the total normalization is accurate to NNLO.

3. Jun 13, 2016

### ChrisVer

So the events get scaled by something like this:
$\frac{\sigma_{LO/NLO}}{\sigma_{NNLO}}$?

4. Jun 14, 2016

### ofirg

The total number of events are normalised by $\frac{\sigma_{NNLO}}{\sigma_{LO/NLO}}$

5. Jun 15, 2016

### RGevo

So practically:

$\sigma_{nnlo}/\sigma_{nlo} d \sigma_{nlo} /dX$

Where X is the observable. Practically though, POWHEG samples are not actually NLO accurate for distributions, since it's NLO+PS (not fixed order).