[Rivet] useInvisibles

[Jonathan Butterworth]

Just to say that all ATLAS analyses except the published W+jets paper 
use neutrinos and muons.

The ATLAS default behaviour is to use all stable particles in the jet 
finder EXCEPT
- prompt leptons
- photons with a cone of 0.1 around prompt charged leptons.

(These photons are generally summed with the lepton four vector instead).

The upcoming (and currently preliminary) W+jets results also use this 
default behaviour.

For technical reasons, this is not strictly implemented like this in all 
published ATLAS analyses, since prompt leptons and the photons are also 
input to the algorithm. But there is always a lepton/jet isolation which 
means that the difference is irrelevant given the local behaviour of 
anti-kT.

Cheers,
Jon


On 08/07/2011 17:58, Andy Buckley wrote:
> I think we need to revisit the jet config interface for the next release
> -- with all the analyses that I know are in preparation and this
> mismatch becoming more obvious by the minute we're clearly going to want
> a 1.6.0. We can look into this when I'm down in Durham in a week or so...
>
> Andy
>
>
> On 08/07/11 17:12, David Grellscheid wrote:
>> Hi everyone,
>>
>> It seems that at the moment, neither of the two options does what ATLAS
>> seems to want. From the code comments:
>>
>>> The default behaviour is that jets are only constructed from visible
>>> (i.e. charged under an SM gauge group) particles. Some jet studies,
>>> including those from ATLAS, use a definition in which neutrinos from
>>> hadron
>>> decays are included (via MC correction) in the experimental jet
>>> definition.
>>
>> If useInvisibles is true, Rivet not only includes the neutrinos from
>> hadron decays, but all invisibles. W+jets analyses should be careful
>> there!
>>
>> See you,
>>
>> David
>>
>>
>> PS: I still do not understand why one would want to correct for an
>> undetectable particle, but we've had that discussion before.
>> _______________________________________________
>> Rivet mailing list
>> Rivet at projects.hepforge.org
>> http://www.hepforge.org/lists/listinfo/rivet
>>
>
>

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Prof. Jonathan Butterworth,              http://www.hep.ucl.ac.uk/~jmb/
Physics and Astronomy Department                  Tel: +44 20 7679 3444
ATLAS, CERN                                       Tel: +41 22 76  72340
University College London                 Gower St, London WC1E 6BT, UK
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