Trigger efficiencies for E+Jets comparing tag and probe electron pairs for which the probe pass HLT cuts with all tag and probe pairs.
The triggers of interest are:
Triggers | L1 Seed | Last Filter |
---|---|---|
HLT_Ele10_LW_L1R | L1_SingleEG5 | hltL1NonIsoHLTNonIsoSingleElectronEt15PixelMatchFilter |
HLT_Ele15_SW_L1R | L1_SingleEG8 | hltL1NonIsoHLTNonIsoSingleElectronEt15PixelMatchFilter |
HLT_Ele15_SW_CaloEleID_L1R | L1_SingleEG8 | hltL1NonIsoHLTNonIsoSingleElectronEt15CaloEleIdPixelMatchFilter |
HLT_Ele17_SW_CaloEleID_L1R | L1_SingleEG8 | hltL1NonIsoHLTNonIsoSingleElectronEt17CaloEleIdPixelMatchFilter |
HLT_Ele17_SW_TightEleID_L1R | L1_SingleEG8 | hltL1NonIsoHLTNonIsoSingleElectronEt17TightEleIdDphiFilter |
HLT_Ele22_SW_TighterEleID_L1R_v2 | L1_SingleEG8 | hltL1NonIsoHLTNonIsoSingleElectronEt22TighterEleIdDphiFilter |
HLT_Ele22_SW_TighterEleID_L1R_v3 | L1_SingleEG8 | hltL1NonIsoHLTNonIsoSingleElectronEt22TighterEleIdDphiFilter |
Data Samples | Run Numbers |
---|---|
Run2010A-Sep17ReReco_v2/RECO | 135821 - 144114 |
Run2010B-PromptReco-v2/AOD | 146240 – 149442 |
To determine the trigger efficiencies, each PAT electron in the MC sample should be matched to an L1 seed or trigger event. This is done in the following way:
The L1 seed matching criteria are derived from Sam Harper's L1 seed matching code, which can be found here. A simple matching for the L1 seed runs into trouble in the endcap, where the x-y geometry means that the crystals are large in eta. A more sophisticated, but also more relaxed cut is required here.
The cuts used are:
Tag:
Probe:
Cuts on Pairs: *Exactly two electrons *Oppositely charged *Invariant mass between 76 and 106 GeV/c^2
Tag/tag pairs are counted as two tag and probe pairs with the tag switched.
The plot overflow has been transferred to the last bin in the histogram.
All efficiency plots were generated by defining a TGraphAsymmErrors
in ROOT, and calling the member function BayesDivide()
. This function takes two histograms (one the numerator and the other the denominator) and computes the efficiencies, while assigning suitable asymmetric errors using Bayesian statistics. Information about the TGraphAsymmErrors
class can be found here, and a paper explaining the computation of the errors (which goes beyond normal binomial distribution errors) can be found here.
Each efficiency plot is fitted with the following function:
In the plots below, p0 = A, p1 = and p2 = s. p0 corresponds to the high limit of the efficiency, the midpoint of the slope, and s the gradient of the slope at .
HLT_Ele22_SW_TighterEleID_L1R
new plots for this trigger here...
TABLE 2 | Barrel | Endcap |
---|---|---|
All electrons | ||
L1 Seed to Electrons Efficiency | ||
HLT to Electrons Efficiency | ||
HLT to L1 Seed Efficiency |
The L1 seed threshold should be at about 8 GeV, with the fit report a threshold of about 9 GeV.
The fit for has been performed only on data points above 12, ignoring the "wiggle" at low . Reading off the value of p0 from the fits, we have at high transverse momentum
TABLE 3 | Efficiencies from fit (Barrel) | Efficiencies from fit (Endcap) |
---|---|---|
0.9998 | 0.9998 | |
0.9943 | 0.9918 | |
0.9941 | 0.9918 |
We should expect that . From Table 2, we obtain for the barrel, and for the endcap.
Comparing the plots shown above, we see that the slopes of the trigger efficiency for the L1 seed and the HLT begin at different transverse momenta: around 5 GeV for the former and 12 GeV for the latter. This accounts for the wiggle that we see in the plot of : at low transverse momentum, both the L1 seed and the HLT have similar efficiencies with respect to all PAT electrons. But between 5 and 12 GeV, the L1 seed is increasingly likely to pass electrons, while the HLT still has the same efficiency as before, leading to a dip in .
TABLE 12 | Barrel | Endcap |
---|---|---|
All electrons | ||
L1 Seed to Electrons Efficiency | ||
HLT to Electrons Efficiency | ||
HLT to L1 Seed Efficiency |
For the L1 seed to electrons efficiency of the barrel electrons, the fit is very poor, despite using several different sets of initial parameters for the fit.
-- HongwanLiu - 16-Jun-2010