[Rivet] CMS_2015_I1397174

[Andy Buckley]

Hi again Markus,

There will be a PartonicTops projection in the upcoming Rivet 2.5.2 
release, and today I went through your analysis code to convert it... it 
looks pretty good, so hopefully we can finally get it into that 
approaching release.

The one thing that looks *really* weird is that the analysis doesn't 
fill the histograms with the event weights, but with their *signs*. That 
will do very strange things in event sets with e.g. weighted kinematic 
enhancement. Is there a reason for it?

I also noticed that your "gap" histograms are filled with 
weight*binwidth, so that the resulting histograms are like bar plots 
(where the width is not physically meaningful) rather than dN/dx 
differential histograms. I've not checked exactly what is being filled, 
but could you quickly verify that this is correct? Is it perhaps a way 
to get the central value (but not error) behaviour of a profile 
histogram via a standard one?

Cheers,
Andy



On 19/07/16 15:38, Markus Seidel wrote:
> Hi Andy,
>
> I hope that future analyses just look for two high-pt leptons and are
> easier to implement then...
> The problem is that many of the 8 TeV analyses explicitly veto W>tau
> decays. In dilepton it should be possible to search for exactly 2
> lepton+neutrino pairs that have a mass close to 80.4 GeV but in
> lepton+jets we would need to be able to identify hadronic tau decays to
> veto lepton+tau(had)+jets on particle level.
>
> In fact, I forgot about the piece of code that deals with additional b
> jets. This is indeed heavily reliant on the HepMC record. We might
> consider splitting it in two analyses...
>
> The b-tag is indeed without cut on the hadron pt. Is there a compelling
> reason for a cut? I think we discussed it once in the LHCTopWG but
> without outcome.
>
> Cheers,
> Markus
>
>
> Am 19.07.2016 um 16:19 schrieb Andy Buckley:
>> Requiring exactly 2 prompt (i.e. not-from-hadron-decay) charged leptons
>> with substantial pT should do 99% of what's required, I think! This is
>> pretty easy to do.
>>
>> But I saw some code in there which also categorises b-jets according to
>> whether they come from top decay or not... so maybe the connection is
>> deeper? Complex "HepMC digging" analyses like this can take a while for
>> us to integrate, because we really need to go through them in detail and
>> make sure everything makes sense & uses appropriate machinery.
>>
>> Andy
>>
>> PS. By the way, is there really no pT cut on the b-hadrons that you
>> consider as tagging a jet? You can use e.g. jet.bTagged(Cuts::pT >
>> 1*GeV), for example, or a similar argument to Jet::bTags()
>>
>>
>> On 19/07/16 15:13, Markus Seidel wrote:
>>> Hi Andy,
>>>
>>> thanks for the feedback!
>>>
>>> Actually, the parton level stuff is needed here only for selecting the
>>> ttbar decay channel (dilepton ee/emu/mumu). Is there a better way to do
>>> that?
>>>
>>> Cheers,
>>> Markus
>>>
>>> Am 19.07.2016 um 15:57 schrieb Andy Buckley:
>>>> On 19/07/16 14:47, Markus Seidel wrote:
>>>>> Hi all,
>>>>>
>>>>> for some reason this analysis did not make it to the mailing list
>>>>> after
>>>>> uploading (in April):
>>>>> https://www.hepforge.org/archive/rivet/contrib/NEW/CMS_2015_I1397174.tgz
>>>>>
>>>>>
>>>>>
>>>>> It contains jet multiplicity, pt, eta, etc... measured in ttbar events
>>>>> at 8 TeV.
>>>>
>>>> Hi Markus,
>>>>
>>>> We've not yet incorporated this one because (as the code acknowledges)
>>>> it uses a non-portable partonic top quark definition and introduces a
>>>> lot of custom machinery that we need to merge carefully into the Rivet
>>>> system.
>>>>
>>>> We've decided to allow partonic top definitions in "official" Rivet
>>>> analyses, but have not provided the central machinery for that yet.
>>>> When
>>>> it is ready, this analysis will still require significant effort to
>>>> include in the distribution... but in the meantime the code is still
>>>> publicly available in the contrib directory for anyone who wants to
>>>> use it.
>>>>
>>>> Cheers,
>>>> Andy
>>>>
>>
>>


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