[Rivet] Use proton-lead MC generators with Rivet

[Van Haevermaet Hans]

Dear Andy and Leif,

Thank you very much! Indeed, I didn’t got the first mail from Leif, but it seems exactly what is needed to avoid the problem.
We will try it out, and if it works, then yes I think it would be very nice if this can be included in one of the next releases.
That will allow then to run Rivet analyses on much more generators with proton-lead or lead-lead beams.

I’m also surprised that no one else encountered this… it seems that we are the first ones to really try it :-)
Hopefully in the near future, we will also be able then to publish routines with pA data from CMS.

Cheers,
Hans

> On 28 Feb 2017, at 16:33, Andy Buckley <andy.buckley at cern.ch> wrote:
> 
> 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

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