[Rivet] Is it possible? Rivet and truth look different

[Andy Buckley]

I don't think it's 100% consistent: it's a choice whether neutrinos are
included, whether all muons or just "prompt" muons are excluded, etc. At
least that's the case for the general set of jet/ETmiss jet collections
(as well as all the algorithm, R parameter, and grooming variations).
The data analyses should be doing the right thing case-by-case for
consistency with the analysis -- and if they aren't then that's a bug
for us/the expt Rivet contacts to fix.

Cheers,
Andy

PS. This makes me think that jet area pile-up correction as applied to 8
TeV ATLAS jets should probably be applied in 8 TeV Rivet analyses as
well: the PU correction also subtracts some portion of the underlying
event activity. I don't think there are any approved ATLAS 8 TeV
measurement analyses to be Rivetted yet, but we should keep it in mind.
I've CC'd the ATLAS "Rivet guys" for their interest and input.


On 10/11/13 17:38, Liron Barak wrote:
> Hi Andy,
> 
> One last question, for the analysis using the data too (like the jet
> fraction etc)....
> Do you use the same jets definitions? Is it consistent in all Rivet
> analyses?
> 
> Thanks
> Liron
> 
> 
> On Sun, Nov 10, 2013 at 5:51 PM, Andy Buckley <andy.buckley at cern.ch
> <mailto:andy.buckley at cern.ch>> wrote:
> 
>     On 09/11/13 19:21, Liron Barak wrote:
>     > Hi Andy,
>     >
>     > On Fri, Nov 8, 2013 at 2:36 PM, Andy Buckley <andy.buckley at cern.ch
>     <mailto:andy.buckley at cern.ch>
>     > <mailto:andy.buckley at cern.ch <mailto:andy.buckley at cern.ch>>> wrote:
>     >
>     >     Ok, well the two sets of curves do look a bit different. Maybe
>     this
>     >     could come from different eta acceptance and changes in Sherpa's
>     >     handling of beam remnant dipoles, etc.
>     >
>     > But then, wouldn't it also be seen in the first plot?
>     >
>     >     In the Rivet plot it looks to me
>     >     like Sherpas 1 and 2 could be ~consistent in the high-stats
>     part, and
>     >     maybe the deviations elsewhere are just statistical jitter:
>     can you make
>     >     the plot again with the --mc-errs option flag, to show the MC
>     error
>     >     bars?
>     >
>     > It is attached... but surprised me is not that the 2 sherpa
>     options are
>     > different, that is kind of expected, no? What worries me is why the
>     > Rivet gave different (actually opposite) answers than simple draw
>     of the
>     > truth jets? If it is because the eta/pt are different, what should I
>     > "believe" to?
> 
>     I suspect both are correct. There is no "right" definition of either jet
>     constituents, jet algorithm, or jet acceptance -- the ATLAS truth jets
>     are not *the* thruth jets, but just one definition, which I suspect
>     doesn't coincide with the one used in that validation Rivet analysis.
> 
>     If you look at the ATLAS data analyses in Rivet, you'll find that the
>     jet setup often involves excluding muons from the jet inputs, and
>     applying an eta cut corresponding to the calorimeters. I'm not sure what
>     eta cut is used in the default ATLAS truth jet collection.
> 
>     In short, "believe" both! And if you need a specific jet definition in
>     Rivet then make your own analysis plugin based on MC_TTBAR (or whatever)
>     with your preferred jet setup.
> 
>     Cheers,
>     Andy
> 
>     --
>     Dr Andy Buckley, Royal Society University Research Fellow
>     Particle Physics Expt Group, University of Glasgow / PH Dept, CERN
> 
> 


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