[Rivet] useInvisibles

[Andy Buckley]

Hi Frank,

Yes, that one is still open. I had been thinking in terms of the task 
being to refactor the FastJets interface to make the required common 
definitions of jet particle content easier, which is a low priority 
thing that could wait for the next next release, but you're right that 
we should fix the currently wrong definitions now.

Can you do this? Feel free to modify the FastJets interface to know 
about muon exclusion, neutrino (but not LSP) inclusion, etc. if the 
alternative would be nasty contortions with IdentifiedFinalStates or 
similar. It's easy to update the FastJets interface in Rivet 2.0 if all 
that needs to be changed is one function call, less easy if a chain of 
projections needs to be refactored!

Andy


On 21/07/11 08:43, Frank Siegert wrote:
> Hi all,
>
> since we were talking about a new release these days, I thought I'd
> mention that this one is still open as far as I know? I have it on my
> TODO list, but haven't managed to fix it yet. Do you think it's
> worth/feasible doing so for the imminent release, at least for the heavy
> flavour analyses where it becomes relevant (I'd probably need a day or
> two to implement and test)?
>
> Frank
>
> On 11/07/11 09:27, Jonathan Butterworth wrote:
>> 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.
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>>>>
>>>
>>>
>>
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-- 
Dr Andy Buckley
SUPA Advanced Research Fellow
Particle Physics Experiment Group, University of Edinburgh

The University of Edinburgh is a charitable body, registered in
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