[Rivet] Rivet Jet Analysis

[Andy Buckley]

There is one last-resort way to find out Pythia 8 features when the
documentation fails... ask the author! :) Torbjörn, does Py8 support
weighted event generation with pT enhancement (yet)? Thanks!

Andy


On 31/01/11 18:56, ST Harnew wrote:
> Thanks for both of your input!
> 
> I will give the rivet-mergeruns script a try tomorrow and see how the
> plots turn out. From looking at all the pT cuts plotted on top of each
> other (see attached) I should end up with a fairly smooth distribution
> with the correct merge points.
> 
> Using weighted events definitely seems like the best option in the long
> run, especially when I start tuning to the UE data and processing time
> becomes more of an issue. I have gone through the Pythia 8 guide and
> can't see any clear way of doing this. Does anyone know a way to do it?
> 
> Many thanks,
> 
> Sam Harnew
> 
> --On 31 January 2011 15:42 +0000 Andy Buckley <andy.buckley at ed.ac.uk>
> wrote:
> 
>> On 31/01/11 15:26, Hendrik Hoeth wrote:
>>> Hi Sam,
>>>
>>> Thus spake Andy Buckley (andy.buckley at ed.ac.uk):
>>>
>>>>> For the CDF_2008_LEADINGJETS  <Nch> against pT(leading jet) plots, the
>>>>> runs from each pT cut are needed to fill a single histogram. Should I
>>>>> deal with this by chopping each histogram down to its valid region
>>>>> (say
>>>>> 0-20 pT for the minimum bias run, then 20-100pT for the pTmin=10GeV
>>>>> run
>>>>> etc) then stick all these together to make a complete distribution? Or
>>>>> is there a smarter way of doing this.
>>>
>>> Currently we do exactly that. There is a script that can do the
>>> histogram slicing and merging for you: rivet-mergeruns. It's a bit
>>> awkward to use, since it's not exactly aimed at end-users, but
>>> nevertheless. Here is how I used it in a recent Pythia-8 production:
>>>
>>> rivet-mergeruns CDF_2008_LEADINGJETS_CKIN0/Rivet.aida:1960:0 \
>>>                 CDF_2008_LEADINGJETS_CKIN10/Rivet.aida:1960:30 \
>>>                 CDF_2008_LEADINGJETS_CKIN20/Rivet.aida:1960:50 \
>>>                 CDF_2008_LEADINGJETS_CKIN50/Rivet.aida:1960:80 \
>>>                 CDF_2008_LEADINGJETS_CKIN100/Rivet.aida:1960:130 \
>>>                 CDF_2008_LEADINGJETS_CKIN150/Rivet.aida:1960:180 \
>>>                 > foo.dat
>>> flat2aida foo.dat
>>>
>>> You have to specify <aidafile>:<energy>:<mergingpT>. Note that you need
>>> to set the histogram merging pT a fair bit higher than the generator
>>> level cut!
>>
>> And also note that the analyses that it applies to and how it merges
>> them is determined not by the command line (which just tells the script
>> which .aida files should be considered as appropriate at which energy
>> and above which pT cut) but by hard-coded declarations in the script
>> itself! That's why Hendrik says that it's not really intended for
>> end-user use... and why I didn't mention it ;) You can hack the script
>> for your own purposes if it doesn't already handle all the analyses that
>> you need... but from what you mentioned in your previous mail, I think
>> it does.
>>
>> However, I still strongly think that pT-enhancement/weighting is a
>> better way. PYTHIA 6 had a limited version of that so *surely* Pythia 8
>> has something... and hopefully more configurable, too. With the approach
>> above, you can only merge multiple runs together inside a single
>> (profile) histogram if that histogram is binned in the pT of a leading
>> jet -- because that is effectively the quantity that the generator-level
>> cut is applied on. But the pT-enhancement method will work for general
>> histograms, and will fill such pT_lead profiles with smooth statistics
>> rather than the sort of sawtooth that comes from merging together
>> different single-cut pT slices.
>>
>> Cheers,
>> Andy
>>
>> -- 
>> Dr Andy Buckley
>> SUPA Advanced Research Fellow
>> Particle Physics Experiment Group, University of Edinburgh
>>
>> The University of Edinburgh is a charitable body, registered in
>> Scotland, with registration number SC005336.
>>
> 
> 
> 
> ----------------------
> ST Harnew
> sh7566 at bristol.ac.uk
> 
> 
> 
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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
Scotland, with registration number SC005336.