Difference: BottomUpUncerts (8 vs. 9)

Revision 92018-04-21 - BenjaminNachman

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META TOPICPARENT name="BenjaminNachman"
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  • blue: These are suggested checks to see if an analysis is sensitive to a given effect. These cases are the "known unknowns" where if the check results in a minor uncertainty it can be treated as such, otherwise further study is required.
  • red: These are brief instructions on how we would go about updating and/or producing a new recommendation for this uncertainty. Also included are the contact details of anyone currently working on this.
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A discussion of the proposals in this twiki was presented at a recent Jet/MET meeting.
 

Inclusive Uncertainties

Cluster Reconstruction Efficiency

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Cluster Fake Rate

Changed:
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Under discussion

Negligible (unless we do constituent-based pileup identification in which case the meaning of fake changes).

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Spurious clusters from pure noise are negligible, but the contribution from pileup clusters can have an important impact on some observables.
 
Changed:
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Procedure: Ignore.
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Based on studies of the cluster multiplicity as a function of pileup, shift mu up and down by 15% instead of the standard procedure that is much less than this.
 

Cluster Energy Scale

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 E_Tile0 = cluster->auxdata<vector >("EnergyPerSampling")[12]; E_EME3 = cluster->auxdata<vector >("EnergyPerSampling")[7]; E_HEC0 = cluster->auxdata<vector >("EnergyPerSampling")[8];
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i_EMax = argmax cluster->auxdata<vector >("EnergyPerSampling")[i];
 

Then, we have the following procedure

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  1. Splitting between HAD and EM:
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(i) Splitting between HAD and EM:
 
vector merged_constituents;
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 end do
Changed:
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  1. splitting in the EM calorimeter of hadronic clusters; for any pair of clusters with the maximum energy in EMB2 or EME2, and EM_PROBABILITY<0.9 (not extremely likely to be a photon), and dR(i,j)<sigma_{eta/phi}^{i}+sigma_{eta/phi}^{j} then we combine them into a single cluster with eta=(eta_i*E_i+eta_j*E_j)/(E_i+E_j), phi=(phi_i*E_i+phi_j*E_j)/(E_i+E_j), E = E_i+E_j
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(ii) Hadronic cluster splitting in the EM calorimeter.

vector merged_constituents;
vector already_merged;
for i in constituents do
      already_merged[i] = false
end do
 
Changed:
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  1. the previous two only look at combining cluster rather than additional splitting. For splitting in the EM calorimeter of hadronic clusters I think I would also like to see what happens if for 20% (this is a guess) of clusters which have maximum energy in EMB2 or EME2, and EM_PROBABILITY<0.9 we split them into two clusters each with half of the total energy at positions eta=eta_0, phi=phi_0 +/- sigma_{eta/phi}/2
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for i in constituents do if (already_merged[i]) continue end if for j in constituents do if i == j continue if (DeltaR(constituent[i], constituent[j]) > sigma[i]+sigma[j]) #close to each other transversely continue if ((EM_PROBABILITY[i] < 0.9 && EM_PROBABILITY[j] < 0.9) && ((i_EMax[i] = 2 && (i_EMax[j] = 2) || (i_EMax[i] = 6 && (i_EMax[j] = 6))) then #for any pair of clusters with the maximum energy in EMB2 or EME2 that are not extremely likely to be a photons. already_merged[i] = true already_merged[j] = true #merged_constituent has eta = (eta[i]*E[i]+eta[j]*E[j])/(E[i]+E[j]), phi = (phi[i]*E[i]+phi[j]*E[j])/(E[i]+E[j]), E = E[i]+E[j] merged_constituents.push_back(merged_constituent) end if end do if (already_merged[i]) merged_constituents.push_back(constituents[i]); end if end do

(iii) Cluster splitting.

vector split_constituents;

for i in constituents do
      if  (rand.Uniform < 0.2 && EM_PROBABILITY[i] < 0.9 && (i_EMax[i] == 2 || i_EMax[i] == 6)) then #20% is just a guess
              #split_constituent1 has eta = eta[i], phi = phi[i] + sigma[i]/2, E = E[i]/2
              #split_constituent2 has eta = eta[i], phi = phi[i] - sigma[i]/2, E = E[i]/2
              split_constituents.push_back(split_constituent1)
              split_constituents.push_back(split_constituent2)
      else
              split_constituents.push_back(constituents[i]);
     end if
end do
  For all of a), b), c), plot the cluster multiplicity and N95 (the number of clusters required to reach 95% of total jet energy) in your jets before and after applying the change in MC, and overlay the data (without any modifications to the data distribution).
 
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