[Rivet] Accessing the impact parameter of pp collisions with Rivet

[Andy Buckley]

On 16/06/16 10:07, Gunnellini, Paolo wrote:
> Dear rivet experts,
>
> I was wondering if it is somehow possible to access the impact parameter
> in pp collisions with Rivet (I am specifically working with P8, where
> this info is ). If I look at the Gen Event, there is no specific method
> for that, but perhaps there is a possible workaround for that.

Hi Paolo,

You mean the impact parameter between the colliding protons, according 
to the MC model? That's not recorded in HepMC (at least not yet, and it 
won't ever be guaranteed), so not available to Rivet. Also, it's not a 
physical observable so it's much better to use another measure, e.g. 
centrality.

Andy

-- 
Dr Andy Buckley, Lecturer / Royal Society University Research Fellow
Particle Physics Expt Group, University of Glasgow