[Rivet] delta phi of jets with sherpa

[Andy Buckley]

Hi Ulrike,

That (pb vs. fb) could certainly lead to discrepancies, but hopefully 
not if you are explicitly specifying -x 1.0 ... unless there is a bug in 
Rivet's xsec override option.

By the way, I think that HepMC specifies that the cross-section should 
be entered as pb: we certainly made sure that a definite unit was 
specified (as opposed to the older vertex and particle 4-vectors) when 
we added cross-section support to HepMC.

Can you try enabling the debug output on rivet, i.e. either -lDEBUG, 
-lAnalysis=DEBUG or -lProjection=DEBUG? This would help to get a picture 
of how many particles and jets are being found in the events from Sherpa 
and Whizard: an obvious disagreement might help to identify the source 
of the problem.

Andy


On 15/09/11 11:54, Ulrike Schnoor wrote:
> Hi Frank,
>
> no, the generators don't give the same total cross section, but they
> are in the same order of magnitude. Also I am using the option -x 1.0
> and normalizing to cross-section/sumofweights.
>
> The units line in the hepmc files show GEV and MM for both. Whizard
> gives its cross-sections in fb, whereas Sherpa gives them in pb,
> perhaps that is the reason for the large difference? Is there a way to
> tell rivet the unit that the generator is using? (Sorry if this is an
> ignorant question.)
>
> Thanks,
> Ulrike
>
>
> 2011/9/15 Frank Siegert<frank.siegert at cern.ch>:
>> Hi Ulrike,
>>
>> this is clearly not a Rivet question, but a generator question. Have you
>> checked whether both generators give the same total cross section for the
>> same cuts? Also, is it possible that the units in the HepMC file are
>> accidently inconsistent with what the generator claims (normally pb and
>> GeV)?
>>
>> Frank
>>
>> On 15/09/11 11:10, Ulrike Schnoor wrote:
>>>
>>> Dear RIVET experts,
>>>
>>> When using RIVET to compare WHIZARD (hepmc files) to SHERPA (hepmc2g
>>> files) I ran into the following problem with the azimuthal angle of
>>> the jets' FourMomentum, which is happening with my own analysis as
>>> well as with MC_WWJETS:
>>> There are far less entries in the jets' phi or delta phi plots for
>>> Sherpa than for Whizard. You can see this in the following plot made
>>> with MC_WWJETS:
>>> http://iktp.tu-dresden.de/~schnoor/rivet/jets_dphi_12.pdf. Has this
>>> happened before, and what could I do to avoid this? I have already
>>> tried to rescale the histograms, with no effect.
>>> The same is happening in my private analysis that also needs the
>>> azimuthal angle of jets. In addition, the MET distributions of the two
>>> generators look rather different as shown in this plot:
>>> http://iktp.tu-dresden.de/~schnoor/rivet/MC_VBS/missingET.pdf
>>> Could this be related to the problem with the jets' phi coordinates?
>>>
>>> Please have a look at this and let me know if you need more information.
>>> Many thanks,
>>> Ulrike
>>> _______________________________________________
>>> Rivet mailing list
>>> Rivet at projects.hepforge.org
>>> http://www.hepforge.org/lists/listinfo/rivet
>>
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-- 
Dr Andy Buckley
SUPA Advanced Research Fellow
Particle Physics Experiment Group, University of Edinburgh

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