[Rivet] CMS RIVET analyses

[Nhan V Tran]

Hi Andy,

Thanks again, comments inline.

On Nov 24, 2013, at 2:13 PM, Andy Buckley wrote:

> Hi all,
> 
> A couple more (minor) questions about this analysis:
> 
> * In the comments it's stated that the Z and W will be selected with pT
>> 125 GeV, but in the code the cut is placed at 120 GeV: which is correct?

The comments are wrong, the cut on the W/Z pT > 120.

> 
> * In the W+jet case, the back-to-back requirement was trying to use two
> constituent charged leptons: there should only be one and I'd have
> expected the code to segfault when it tried to access the second.

This might be my own misunderstanding of the WFinder, but I took the l2 to be the neutrino which I used to define the Phi angle between MET and jet.  It's been a while since I did this so I can't now remember why I came to this conclusion. 

> And
> the back-to-back requirements were being applied the wrong way around
> anyway: I've fixed all these things, but how was the analysis validated?

The analysis was validated by comparing a sample MC set against the data HepMC but I guess the sample was pretty small unfortunately.

Best,
Nhan

> Since there was a request to know what CMS analyses are just about to
> appear in the next Rivet version, I thought I'd also point out that we
> have three "preliminary" CMS analyses in the code which it would be
> great to upgrade to their published equivalents:
> 
> if ENABLE_PRELIMINARY
> RivetCMSAnalyses_la_SOURCES += \
>    CMS_QCD_10_024.cc \
>    CMS_2012_PAS_FWD_11_003.cc \
>    CMS_2012_PAS_QCD_11_010.cc
> endif
> 
> Any chance that you could get these ones to us (or if they are already
> fine other than the name and ref data, let us know the Inspire IDs).
> 
> Thanks again,
> Andy
> 
> 
> 
> On 22/11/13 20:37, Hannes Jung wrote:
>> Dear Nhan (cc Andy et al)
>> 
>> I just forward this mail thread to our Rivet coordinators  Lars & Albert
>> 
>> Cheers
>> Hannes
>> 
>> On 22.11.2013, at 18:16, Nhan V Tran <ntran at fnal.gov> wrote:
>> 
>>> Hi Andy,
>>> 
>>> Thanks for the detailed reply!  More inline...
>>> 
>>>>> Thanks for following up on the CMS jet mass RIVET routine last week.  I forgot to ask you, one of the other CMS conveners was asking me...
>>>>> 
>>>>> Can you let me know what CMS analyses are in the RIVET queue and what's the expected time to be included?
>>>> 
>>>> Hi Nhan, (and CC'ing the Rivet dev list)
>>>> 
>>>> I finally got time today to really spend some time on incorporating the
>>>> various new analyses for Rivet 1.8.4. We'll release this very soon,
>>>> followed as soon as we can by an equivalent 2.0.1.
>>>> 
>>>> There are two CMS analyses in our queue: your jet mass one, and
>>>> CMS_2013_I1258128.cc (rapidity distributions in Z+jet and gamma+jet
>>>> events). If there are more that we can include right away, now is the
>>>> time to let us know!
>>> 
>>> Thanks, will let you know if there are any other CMS requests.
>>> 
>>>> I have a few questions/comments about your analysis, actually: we don't
>>>> just copy them into place but do a bit of code checking and clean-up
>>>> first... which is why it's usually not a 100% straightforward operation.
>>>> A bit annoying, I know, but once we've got them in the system we have to
>>>> maintain them... hence we sometimes ask for fixes and clarifications!
>>>> Ok, here goes:
>>> 
>>> Thanks for taking the time.  This is our first RIVET analysis, so I'm very happy to have an expert take a look ;)...
>>> 
>>>> * I've split the analysis into three separate analyses, with _ZJET,
>>>> _WJET, and _DIJET suffixes. The _ZJET one is the one that I've tidied up
>>>> so far (e.g. putting the pT bin searching into a function really
>>>> compresses the code blocks for the three jet types), and I've attached
>>>> it for your interest. (It quite possibly doesn't compile right now: it's
>>>> the code logic that I'd like feedback on, if you have any.)
>>> 
>>> This is perfect for me. 
>>> 
>>>> * 2D histos will coming soon in Rivet v2 / YODA. They are an order of
>>>> magnitude more fiddly than 1D ones, if you really want to handle
>>>> overflows and so-on nicely. I though that they worked already in Rivet
>>>> v1, though... but HepData doesn't (yet) support them so I think this 1D
>>>> slice approach is better anyway.
>>> 
>>> I agree, it's fine to keep the 1D slides.  
>>> 
>>>> * There is a bit of code to treat any negative weights as equivalent to
>>>> 1.0. Why is that? I expect it's a bad idea, especially with more NLO
>>>> simulations becoming normal, but I wanted to check rather than just
>>>> remove it.
>>> 
>>> I think it's fine to remove.  I'm not sure if it was there for some protection (Sal put this in), but you make a good point about the NLO simulations.
>>> 
>>>> * The back-to-back requirement between the W/Z and the leading jet i
>>>> actually applied in reverse:
>>>> 
>>>> // Get the leading jet and make sure it's back-to-back with the Z
>>>> const fastjet::PseudoJet& j0 = psjetsCA8_zj[0];
>>>> if (!isBackToBack_zj(zfinder, j0)) { //< @todo ARGH!?!
>>>> 
>>>> (This is my tidied version of the code, but I checked that this isn't a
>>>> problem that I introduced!) Is this a (repeated) typo, or is the
>>>> back-to-back cut *really* meant to work this way round? (Which would be
>>>> strange.) The isBackToBack function contents do match its name.
>>> 
>>> Good catch, please reverse it! 
>>> 
>>>> * Lastly, something on which we'll maybe need input from other Rivet
>>>> developers: you're using explicitly FastJet3 functionality to groom the
>>>> jets. That's great: you've written the first official experiment Rivet
>>>> analysis to require FJ3! But it means that we will need to require FJ3
>>>> for any Rivet version which includes this analysis... which we currently
>>>> don't do. I think we can happily do that for Rivet version 2, but
>>>> perhaps it's not the best idea to make that change in our last ever 1.x
>>>> minor version.
>>>> 
>>>> I suggest that we release Rivet 1.x with the existing FJ > 2.x
>>>> requirement, and also make your analysis code public on the Rivet
>>>> website for FJ3 users to build. Or we could make a special exception and
>>>> build the analysis only if FJ2 is present: that might be the neatest
>>>> option. For Rivet 2.0.1 we can make FJ3 a build requirement: I think it
>>>> is time for that anyway, but thanks for giving us a concrete reason to
>>>> do so!
>>> 
>>> I have seen the continuing thread from the other developers and your solution sounds good for me
>>> 
>>> Thanks a lot!
>>> Best,
>>> Nhan
>>> 
>>> 
>>>> 
>>>> Cheers, and please let me know about those queries in the code and if
>>>> you have any other feedback on the "tidied" version: once I know what to
>>>> do I'll carry on doing similar tidying for the _DIJET and _WJET source
>>>> files.
>>>> 
>>>> Andy
>>>> 
>>>> -- 
>>>> Dr Andy Buckley, Royal Society University Research Fellow
>>>> Particle Physics Expt Group, University of Glasgow / PH Dept, CERN
>>>> <CMS_2013_I1224539_ZJET.cc>
>>> 
>>> _______________________________________________
>>> Rivet mailing list
>>> Rivet at projects.hepforge.org
>>> http://www.hepforge.org/lists/listinfo/rivet
>> 
>> ***********************************************************************
>> Hannes Jung 
>> Email: Hannes.Jung at desy.de 
>> mobile :+49 40 8998 93741
>> http://www.desy.de/~jung                                  
>> Tel: +49 (0) 40 8998 3741         
>> Fax: +49 (0) 40 8994 3741
>> DESY, CMS 01B/02.213
>> Notkestr.85, 22603 Hamburg, FRG   
>> ***********************************************************************
>> 
>> 
>> 
>> 
>> 
> 
> 
> -- 
> Dr Andy Buckley, Royal Society University Research Fellow
> Particle Physics Expt Group, University of Glasgow / PH Dept, CERN