[Rivet] Rivet Query

[Debarati Roy]

Hi Andy,
              Thanks for your feedback. First of all I would like to give you some more information regarding these hardonic event shape calculations applied in this analysis .

 In this analysis for the calculation of the five hadronic event shapes always the input variables we used are jet Px, Py, Pz and E. In some of them we do not require that Pz component like the thrust, total jet broadening. 

Now regarding your comments,
For the total jet broadening I think your calc method can be useful since we have used only transverse component of momentum along with jet eta and phi.
But for the total jet mass the concept is very similar as  used in Hemispheres.cc for mass2With and mass2Against. The difference exists in the input(always jet's four momentum) and then total jet mass is the sum of  mass2With and mass2Against(this one I called as M2sum() in my previous mail). For the total transverse jet mass I think the same method can work only again in transverse plane(Z component set to 0).  So over all I would say the jet hemisphere projection will cover all:  broadening(setZ=0), total jet mass, total transverse jet mass(setZ=0) with jet's four momentum as inputs.
If the jet hemisphere  you do not think should be added as a projection then I can try with the analysis code.

Please let us know your view.  

Regards,
Debarati
________________________________________
From: Andy Buckley
Sent: 15 August 2014 01:09
To: Debarati Roy; rivet at projects.hepforge.org
Cc: Albert Knutsson; Maxime Gouzevitch; Lars Sonnenschein
Subject: Re: [Rivet] Rivet Query

Hi Debarati,

Those hemispheres are an e+e- observable, so I'm a bit surprised that a
non-transverse decomposition work at a hadron collider... but then I'm
not a hadronic event shapes expert. Are you using the jets to build a
"3D" hemispheres observable, or do you want to set the jet z-components
to zero and then run the hemispheres algorithm?

If the latter, I guess we could expose a "calc()" method on the
projection so it can be used directly rather than via applyProjection --
this is sometimes done with the FastJets projection, for example.

If the former, then maybe we should supply a JetHemispheres projection
instead. It might be easier to just implement in the analysis code,
though, since projections are only really necessary for code that's
likely to appear in several analyses and which would benefit from caching.

I'd be happy to add a M2sum() method if you can define what it should do.

Cheers,
Andy


On 14/08/14 16:10, Debarati Roy wrote:
> Hi Experts,
>                  I need some feedback regarding an analysis which we are
> planning to introduce in Rivet. It is a CMS analysis consists of the
> study of hadronic event shapes (arxiv link :
> http://arxiv.org/abs/arXiv:1407.2856).
> In this analysis five event shapes are studied, thrust, total jet
> broadening, total jet mass, total transverse jet mass, jet resolution
> parameter where each of the event shape variable is calculated by giving
> the input of final state jets momenta . I found that Rivet already has
> the thrust projection where jets momenta of an event can be given as
> input to calculate thrust.  But for other three variables (total jet
> broadening, total jet mass, total transverse jet mass) I observed that
> you have a similar but not identical projection named,
> https://rivet.hepforge.org/trac/browser/src/Projections/Hemispheres.cc
> In this projection you are taking the final state particles to calculate
> broadening and mass if I am not wrong whereas in this analysis the final
> state jets momenta are used. So is it possible to modify the existing
> projection to be more flexible so that we can run it over the final
> state jets too? Or is it possible that a different projection with a
> different name can be added?
>  Also here
> https://rivet.hepforge.org/trac/browser/include/Rivet/Projections/Hemispheres.hh
> I could see that there exists different methods  M2high(), M2low(),
> M2diff(). Is it possible to introduce M2sum() as per this analysis
> requirement?
>
> Please let us know.
>
> Thanks,
> Debarati
>
>
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--
Dr Andy Buckley, Royal Society University Research Fellow
Particle Physics Expt Group, University of Glasgow / PH Dept, CERN