[Rivet] Use proton-lead MC generators with Rivet

[Andy Buckley]

Aah, I understand better now. I thought it was the .info file beams 
requirement that was causing trouble. I had forgotten that long-ago we 
put in a check to insist that all events in a run have the same beams.

Indeed it would make sense to also drop that check in "ignore beams 
mode". If I can work out a patch that implements that easily, would you 
be able to patch your current Rivet build? Obviously another Rivet 
release will be required to make it out-of-the-box.

I'm very surprised that we never had this reported before, given I was 
in touch with the Epos authors about putting improvements in! I guess 
they were just using it for nucleon collisions so far.

Andy



On 28/02/17 14:47, Sercan Sen wrote:
> 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
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Rivet mailing list
>>> Rivet at projects.hepforge.org
>>> https://www.hepforge.org/lists/listinfo/rivet
>>>
>>
>>
>> --
>> Dr Andy Buckley, Lecturer / Royal Society University Research Fellow
>> Particle Physics Expt Group, University of Glasgow
>


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