[Rivet] correction on ATLAS_2011_I944826 routine

[Andy Buckley]

On 23/10/12 12:22, Sercan Sen wrote:
> 
> Hi Frank, 
> 
>> Maybe I can ask a follow-up question... if we
>> extend the cfs acceptance, this would also affect the nstable>2 cut
>> (which would now also count particles in the extended acceptance).
>> Would that be correct?
> 
> Right. "nstable" part should be in |\eta| < 2.5 . So, if we extend the
> rapidity acceptance in the CFS projection, then we should apply a
> rapidity cut in the "nstable" part.. you know, something like below.
> 
>       int n_stable = 0;
>       foreach (const Particle& p, cfs.particles()) {
>         const PdgId pid = abs(p.pdgId());
> */        const double eta = fabs(p.momentum().eta());/*
> */if (inRange(eta, -2.5, 2.5)) continue;/*
>         if (pid == 11 || pid == 13 || pid == 211 || pid == 321 || pid ==
> 2212) n_stable++;
>       }
> 
> or we can keep the CFS projection as it is and another projection can be
> applied for the trigger requirement: * "ChargedFinalState  trigfs(-2.09,
> 3.86, 100*MeV);"*
> *
> *
> By the way, I don't know if we need 100*MeV for ATLAS MBTS requirement
> (this is applied in the current code) ? Probably, we don't need it but
> this should be checked by someone from ATLAS..

I don't think there is such a threshold. or if there is it's very low.
I've never noticed it in any of the ATLAS minbias/diffractive
papers/notes, at least. Emily, in CC, will hopefully know for sure.

By the way, if there _is_ such a cut I expect it'll be on lab frame
energy rather than pT: cuts on transverse quantities make sense for
tracks because of the magnetic field alignment... but for energy
deposition detectors like calorimeters and scintillators I think the
total energy is the relevant thing.

[Aside: I'm often surprised by how uncritically we use pT as a measure
of 'energeticness' -- once upon a time the ATLAS detector simulation had
a big problem with nightly test jobs that sampled electrons with fixed
pT across a flat |eta| up to 6. Every now and again, this produced a *40
TeV* electron that would just shower forever in the forward calorimeter!
Detectors don't always rate boost-invariant quantities as highly as
physicists do ;-) ]

Andy


> On Oct 23, 2012, at 11:15 AM, Frank Siegert wrote:
> 
>> Hi Sercan,
>>
>> Thanks for noticing this inconsistency. I take it, you're familiar
>> with the analysis? Maybe I can ask a follow-up question... if we
>> extend the cfs acceptance, this would also affect the nstable>2 cut
>> (which would now also count particles in the extended acceptance).
>> Would that be correct? If so, I'll make the change in the cfs
>> constructor directly.
>>
>> Cheers,
>> Frank
>>
>> On 23 October 2012 11:08, Sercan Sen <Sercan.Sen at cern.ch
>> <mailto:Sercan.Sen at cern.ch>> wrote:
>>>
>>> Hello,
>>>
>>> I think there is a small correction needed on ATLAS_2011_I944826 routine.
>>>
>>> It applies charged final states projection for the particles in |\eta| <
>>> 2.5, however, search for the hits in MBTS rapidity region 2.09 < |\eta| <
>>> 3.84. see below.. In this case, trigger cut is limited to the
>>> 2.09<|\eta|<2.5.
>>>
>>>      ChargedFinalState  cfs(-2.5, 2.5, 100*MeV);
>>>      addProjection(cfs, "CFS");
>>>
>>>      const ChargedFinalState& cfs =
>>> applyProjection<ChargedFinalState>(event, "CFS");
>>>
>>>      // ATLAS MBTS trigger requirement of at least one hit in either
>>> hemisphere
>>>      const ChargedFinalState& cfs =
>>> applyProjection<ChargedFinalState>(event, "CFS");
>>>      int n_mbts = 0;
>>>      foreach (const Particle& p, cfs.particles()) {
>>>        const double eta = fabs(p.momentum().eta());
>>>        if (inRange(eta, 2.09, 3.84)) n_mbts++;
>>>      }
>>>
>>>      if (n_mbts < 1) {
>>>        MSG_DEBUG("Failed trigger cut");
>>>        vetoEvent;
>>>      }
>>>
>>> Cheers,
>>> Sercan
>>>
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>>> Rivet at projects.hepforge.org <mailto:Rivet at projects.hepforge.org>
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> 
> 
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-- 
Dr Andy Buckley, SUPA Advanced Research Fellow
Particle Physics Expt Group, University of Edinburgh

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