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Hi all,<br>
<br>
I am currently working on the LHCB analysis recently added to
contrib (LHCB_2015_I1333223).<br>
<br>
It's pretty straight forward what they do except for one cut in
their phase space definition, namely<br>
a cut on "Distance of Closest Approach in z" i.e. z_0 wrt the
primary vertex. They use that<br>
to define prompt particles by requiring this cut to be <0.2 mm.
(Which is much better I think<br>
than the whole pythia decay times map that was used in other
analyses).<br>
<br>
The way it's implemented right now is heavily using genEvent() stuff
such as<br>
<ul>
<li>finding primary vertex</li>
<li>finding particle production vertices</li>
</ul>
<p>and using that information to calculate z_0.<br>
</p>
<p>Now I don't think that this horribly wrong at all but it would be
nice to <br>
have a more Rivet like way of doing this, maybe having a
Particle.z0()<br>
function? Not sure though.<br>
</p>
<p>What do you think?<br>
</p>
<p>Thanks,<br>
Holger<br>
</p>
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