[Rivet] CDF photon clustering

[Andy Buckley]

Emily Nurse wrote:
> Hi Andy,
> 
> I am waiting to be forwarded the e-mail exchange that lead to the
> conclusion of R=0.2 cone,.
> As I said in the ticket:
> http://projects.hepforge.org/rivet/trac/ticket/247

Ah, ok. I thought Hendrik had sent that to you. I don't think we reached
a conclusion about R = 0.2 in the email discussions, but that was what
Gavin Hesketh and I used for the D0 Drell-Yan analyses. This may be just
because D0 publish what they observed in those cones, rather than some
unfolding of PHOTOS corrections as CDF do. "Say what you see", as they
used to say on Catchphrase ;)

> I think that we need to cluster in all photons that would have been
> simulated by Photos (difficult to define, but I think 0.2 is too small).
> Can someone forward me that email exchange asap? I am at Fermilab now
> and can get to the bottom of it.

I've copied you on an email to Peter about what he did in the end,
although he may be using the Pythia event record directly. The most
important bit of the earlier discussion is quoted in that email.
Hopefully we'll get this sorted out soon... I think that a cone should
give us a ~95% acceptable match to CDF's procedure, and if CDF's
published measurements are still polluted by model-dependent unfoldings
then we might just prefer to use D0's Run II Z pT measurement for tuning
constraints on ISR... assuming that the 0.2 cone really does match to
the measurement in that case.

Andy

-- 
Dr Andy Buckley
Institute for Particle Physics Phenomenology
Durham University
0191 3343798 | 0191 3732613 | www.insectnation.org