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

[Liron Barak]

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> 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>> 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
>
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