[Rivet] Problems when simulating an analysis

[Chiara Zampolli]

Hi James,


On Apr 19, 2013, at 11:54 AM, James Monk wrote:

> 
> On 19 Apr 2013, at 11:01, Chiara Zampolli wrote:
> 
>> Dear James,
>> 
>> 	Thanks for your reply!
>> 
>>> 	When you generate the Pythia events, make sure the particle lifetime cut is consistent in the ALICE analysis and your standalone Pythia run.  Experiments typically generate events with a ctau (lifetime) cut of 10mm, meaning that any particle whose species has an average lifetime of more than 10mm will not be decayed, but this setting may well not be present in a standalone run of Pythia unless you set it yourself.
>>> 
>> 
>> I will check, this might be a good point in fact. How to I set this in Rivet in case?
> 
> It's a generator setting, not a Rivet one.  Assuming, as it appears, that you are using AGILe and Pythia 6 then you need
> 
> 	-p "MSTJ(22)=2" 
> 
> will set a ctau of 10mm (the commonly used value).  If you need another ctau then add PARJ(71)=xx to set it
> 

Ok, I thought it was a cut for the counting of the final states. 

>> agile-runmc Pythia6:426 --beams=LHC:7000 -p "PYTUNE=100" -n 1000000 -o /tmp/zampolli/hepmc_TuneA_7TeV.fifo &
>> 
>> The fact that including or excluding the weight gives me differences means that the generators assigns weights to the events. Even though you write that min bias generation should not… ???
>> So, in any case the safest is that I simply do not include them, since as you say for MB events there should be no weight. 
>> 
> 
> No - you should keep the weights in the histogram filling and find out why you are generating weighted events when you don't intend to!  When I run the command you list there I only see weights of 1, as I would expect. Have you checked the HepMC file to see what the weights are (or even filled a histogram of weight values).  The weight in the HepMC file should be the last number on the line beginning with "E."
> 

They are all 1, in fact. I will cross check again. Maybe I messed up something.. 

> Note also that the command you list there does not include diffractive processes, whereas the ALICE sample may or may not include those processes - you may need to be more explicit in your command to generate exactly the same setup used by ALICE.  I expect the generator experts on ALICE will be able to help you with that.
> 

Thanks! I will then ask ALICE experts what I should add.

Cheers,

	Chiara

> cheers,
> 
> James
> 
> 
>> Thanks and cheers,
>> 
>> 	Chiara
>> 
>> 
>>> 
>>> cheers,
>>> 
>>> James
>>> 
>>> 
>>> 
>>> On 19 Apr 2013, at 10:07, Chiara Zampolli wrote:
>>> 
>>>> Dear all,
>>>> 
>>>>      I am attaching here the files for an analysis that I am trying to perform with Rivet. When I compared the results with Rivet 
>>>> with those that I obtain runnin
>>>> g with the ALICE analysis tools (at MonteCarlo level), with the same Pythia tune, I obtain different 
>>>> results (see attachment). The analysis is meant to produce the multiplicity distributions of charged particles with eta in [-0.8, 0.8], pt > ptcut, 
>>>> for ONLY the events with at least one such particle. The ptcut value can be 0.15, 0.5 or 1 GeV/c, and they correspond to the three histograms of the analysis.
>>>> 
>>>>      Could someone please take a look at the analysis I wrote (which is very short) and see if I made any mistake there? I tried to check the standard analysis (the one not with Rivet), 
>>>> and there I cannot find anything weird… Even though I might be wrong, of course. But if i could exclude that the problem is in the Rivet code, it would be helpful.
>>>> 
>>>> I have also noticed that if I remove the weight in the filling of the histograms, I obtain different results (see further attachment for two out of the three histograms created in my analysis). 
>>>> What is this "weight"? How is it calculated? I thought it was equal to 1.
>>>> 
>>>> Thanks in advance for your help, and Regards,
>>>> 
>>>>              Chiara
>>>> 
>>>> 
>>>> <ComparisonWithRivet.png>
>>>>      I am attaching here 
>>>> <PastedGraphic-5.png>
>>>> the files for an analysis that I am trying to perform with Rivet. When I compared the results with Rivet 
>>>> with those that I obtain running with the ALICE analysis tools (at MonteCarlo level), with the same Pythia tune, I obtain different 
>>>> results. The analysis is meant to produce the multiplicity distributions of charged particles with eta in [-0.8, 0.8], pt > ptcut, 
>>>> for ONLY the events with at least one such particle. The ptcut value can be 0.15, 0.5 or 1 GeV/c. 
>>>>      Could you please take a look at the analysis I wrote (which is very short) and see if I made any mistake there? Or if there 
>>>> is someone else to whom I
>>>> should better write, could you please let me know?
>>>> 
>>>>      Thanks in advance, and sorry to bother you again.
>>>> 
>>>>              Chiar
>>>> <ALICE_2013_DRAFT_Mult_7.cc><ALICE_2013_DRAFT_Mult_7.info><ALICE_2013_DRAFT_Mult_7.plot>_______________________________________________
>>>> Rivet mailing list
>>>> Rivet at projects.hepforge.org
>>>> http://www.hepforge.org/lists/listinfo/rivet
>>> 
>> 
>