[Rivet] missingEt variable in WFinder constructor

[Andy Buckley]

On 03/02/15 14:26, Inês Ochoa wrote:
> Hi Andy, Frank,
> 
> Great, thanks a lot!
> 
> Before updating to the new Rivet version, I assume placing the cut at
> zero and cutting instead on the pT of constituentNeutrinos()[0] is a
> safe option.

Yes, for single W events that will be safe. The non-W-neutrino
contribution to MET is relatively very small. The slightly more
experiment-like alternative is to use the MissingMomentum projection and
make a cut on mm.vectorEt().mod()

Andy


> On 03/02/15 01:17, Andy Buckley wrote:
>> [Oops, I thought this was sent _many_ hours ago...]
>>
>> On 02/02/15 15:49, Frank Siegert wrote:
>>> Hi Andy,
>>>
>>> On 2 February 2015 at 16:43, Andy Buckley <andy.buckley at cern.ch> wrote:
>>>> Hi Ines,
>>>>
>>>> This must be a meaning of "simpler version" that I'm not familiar with!
>>>> I've attached a real minimal working example ;-) The version you
>>>> provided did not compile with the latest version of Rivet, so I guess
>>>> you are using an old one: which version?
>>>>
>>>> Anyway, with my cut-down analysis I can reproduce the problem. I
>>>> added a
>>>> printout line to WFinder.cc and see that the value that we are using as
>>>> an ET cut is much larger than the neutrino pT:
>>>>
>>>> Rivet.Projection.WFinder: DEBUG  W- reconstructed from:
>>>>     (599.426; 30.861, -0.00629191, 598.631) 13
>>>>   + (114.54; -28.4288, 0.264693, 110.956) -14
>>>> Rivet.Projection.WFinder: DEBUG  Scalar ET = 131.66 GeV vs. required =
>>>> 20 GeV
>>>> Rivet.Analysis.MinimalAnalysis: INFO  pT_nu1 = 28.43 GeV
>>>>
>>>> This looks like a projection bug to me -- I need to look into the
>>>> definition of the MissingMomentum projection that we're using,
>>>
>>> Thanks for looking into it.
>>>
>>> Is this an event with only one neutrino where it's obvious that/where
>>> something is going wrong?
>>>
>>>> but
>>>> surely missing ET needs to be a vector rather than scalar quantity.
>>>> This
>>>> is even suggested in the code comments:
>>>>
>>>>      /// @todo Restrict missing momentum eta range? Use vectorET()?
>>>>
>>>> Frank, should I change this:
>>>>
>>>>      if (vismom.scalarEt() < _etMiss) {
>>>>
>>>> to use vectorEt instead?
>>>
>>> I'm afraid you'll have to ask Andy whether he's happy with such a
>>> change ;-)
>>> https://rivet.hepforge.org/trac/changeset/e7fba2de73c390c478d94c0c4849bd9cd543d332
>>>
>>
>> Ha! I'll run a few checks and ask myself ;-)
>>
>>> But it sounds fine to me.
>>
>> Cool, thanks.
>>
>> Ines, this *really* means that you'll want to update to the next Rivet
>> version! Which should probably happen fairly soon.
>>
>> Andy
>>


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