[Rivet] Use proton-lead MC generators with Rivet

[Sercan Sen]

Hi Andy,

We did try --ignore-beams and --nskip options before but didn't help. Now trying again with the following steps:

I copy one of the standard analysis in Rivet, CMS_2015_I1356998<http://i1356998.cc/>, to my working directory and modify the info file like the following,

Beams: [ANY, ANY]
Energies: [13000]

compile the plug-in and run over this hepmc file "http://cern.ch/ssen/Rivet/epos_pPb.<http://cern.ch/ssen/Rivet/epos_pPb.hepmc>txt" which has 20 proton-lead events generated with Epos-LHC.

I use --ignore-beams option but still get the error below.

Event beams mismatch: [PROTON, NEUTRON] @ 13000 GeV vs. first beams [PROTON @ (6500; 0, 0, 6500) GeV, PROTON @ (6500; 0, 0, -6500) GeV] @ 13000 GeV

The output of the line below shows that there are 7 p-p events and  13 p-n events in the hepmc file.
grep -e "P 2 2212" epos_pPb.txt
grep -e "P 2 2112" epos_pPb.txt

I use Rivet 2.5.3, and also try the same steps with my own analysis but the error is the same.

Thank you for your further suggestions
Sercan


On Feb 28, 2017, at 2:40 PM, Andy Buckley <a.g.buckley at gmail.com<mailto:a.g.buckley at gmail.com>> wrote:

Hi Hans,

The rivet command-line tool has an --ignore-beams option for this sort of reason. But you haven't said what analysis you are trying to run: if it's one that you're writing yourself, just use ANY rather than PROTON in the Beams specification in the analysis' .info file.

We've been upgrading tools for HI and cosmic-ray analysis over the last year, so are hoping to start building up the collection. Very happy to help with anything that's currently a blocker!

Andy


On 28/02/17 11:10, Hans Jozef H Van Haevermaet wrote:
Dear Rivet authors,

I am a member of CMS (forward and small-x community in fact), and I’m
trying to get Rivet running with proton-lead events coming from the EPOS
MC generator.
It turns out however, that this is not possible (?).
When executing Rivet, it stops because it detected that the incoming
beams are different for each event:
Event beams mismatch: [PROTON, PROTON] @ 1.87656 GeV vs. first beams
[NEUTRON @ 2511.57 GeV, NEUTRON @ 2511.57 GeV] @ 1.87914 GeV

This in turn, is caused by the fact that the EPOS generator writes out
the interacting nucleon (p or n) in the HEPMC file, and not the particle
id code of lead itself.

Could you let us know if it is possible for Rivet to get compatible with
these kind of situations?
One direct option (for me) is to comment out this function:
https://rivet.hepforge.org/code/dev/AnalysisHandler_8cc_source.html
At line 95.

But that can lead to unwanted behaviour in other cases, I guess. Maybe
one can include a parameter to turn this check on/off? So that it is the
user’s responsibility? i.e. by default the check is done, but the user
can turn it off manually if needed.

It would be very good to solve this incompatibility, since in CMS we try
to get Rivet routines from all our analyses, and it would be nice to be
able to extend this to proton-lead, or even lead-lead measurements. As
far as I can see on the web, I did not find any Heavy Ion analysis
implemented in Rivet?

Thanks!
Best Regards,
Hans




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

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