5.5 Validation of the GS calibration using data
5.5.3 Dierences between data-based and Monte Carlo-based GS corrections
as a function of fTile0, fLAr3, fPSand the jet width for jets at the EM+JES scale with 80 < pjetT <
110GeV and |η| < 0.6. The truth asymmetry used is the one from the reference Pythia sample.
The disagreement between data and the reference Pythia sample in this bin is 2.5% at worse.
Similar results are found in the others bins for the layer fractions. For the width, disagreements of up to 2% are found in other regions except for 1.7 < |η| < 2.1, where disagreements of up to 5% are observed for low values of the jet width.
The asymmetries in data shown in Figure5.13, and the corresponding asymmetries in other pjetT and |η| bins, are used to derive data-based corrections. Figure 5.14 compares the average jet response calculated using the truth jet (using Equation 5.2) as a function of ptruthT after the Monte Carlo-based and data-based corrections are applied to the reference Pythia sample.
The uncertainties are bigger when applying data-based corrections than when applying MC-based corrections. Given that the sample used is the same (the reference Pythia sample), the dierence comes from the fact that the uncertainty on data-based corrections are bigger. The calculation of the uncertainties on data-based corrections is described in AppendixC. Figure5.13 provides a quantitative measure of how dierences between the data and Monte Carlo simulation impact the jet energy scale and could be used (in combination with results in Section 5.4.2) in the future to establish a systematic uncertainty for GS due to changes in the topology and avor composition. After the rst two corrections in Table 5.1 the response changes by less than 1%
for data-based and Monte Carlo-based corrections. The response changes by an additional 1%
to 2% after the third (fPS) and the fourth (width) corrections are applied in the barrel. The agreement in the end-cap is within 2% (4%) for ptruthT > 60GeV (< 60 GeV).
The jet transverse momentum resolution calculated using the truth jet (using Equation5.2) as a function of ptruthT after the Monte Carlo-based and data-based corrections are applied to the reference Pythia sample is shown in Figure5.15for the dierent detector regions. The resolution improvement when using the data-based corrections are comparable with the one achieved when using MC-based corrections for |η| < 1.7. For |η| > 1.7 the improvement is smaller. The dierence is due to the dierence in the width distribution between data and simulation as will be discussed in next section.
Figure 5.16shows the average jet response after applying data-based GS corrections to the simulation in bins of width 0.1 in |η| for 80 < ptruthT < 110 GeV and 260 < ptruthT < 310 GeV.
As explained in Section 5.5.1 (see Table 5.5), data-based corrections have been determined in wider |η| regions than Monte Carlo-based corrections. The application of data-based corrections therefore introduces a variation of the response with |η|, as can be seen from Figure 5.16. They re ect the limitations of the di-jet balancing method given the statistics available at the time this study was performed.
Data-based corrections have been also derived with truth asymmetries coming from the Pythia Perugia2010 and Herwig++ samples shown in Figure 5.12. These corrections are then applied to the reference Pythia MC10 sample and the response they yield is compared to the response obtained after applying the reference data-based corrections using the truth asym-metry from the reference Pythia MC10 sample. The dierence in response is found to be lower than 1% in all the pjetT and |η| bins where the statistical uncertainty is su cient to derive such a number (except for 1.2 < |η| < 1.7 and 60 GeV< pT <80 GeV where the dierence is found to be around 4%) as can be seen in Figure 5.17for |η| < 0.6 and 1.2 < η < 1.7.
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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Figure 5.13: Dierence between the average reconstructed asymmetry and the truth asymmetry in data (open circles) and in the reference Pythia sample (full circles) as a function of (a) fTile0, (b) fLAr3, (c) fPSand (d) the jet width of the probe jet. The lower part of each gure shows the dierences between data and Monte Carlo simulation. The jets used have 80 < pjetT < 110 GeV and |η| < 0.6 and are calibrated with the EM+JES scheme.
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Figure 5.14: Average jet response calculated using the truth jet as a function of ptruthT after applying corrections derived from the nominal Pythia sample (black triangles) and data (red circles) for jets with (a) |η| < 0.6, (b) 0.6 < |η| < 1.2, (c) 1.2 < |η| < 1.7, (d) 1.7 < |η| < 2.1 and (e) 2.1 < |η| < 2.8. Dierences between data and Monte Carlo simulation responses are shown at the bottom of each gure.
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(a) (b)
(c)
(d) (e)
Figure 5.15: Jet transverse momentum resolution calculated using the truth jet as a function of ptruthT after applying corrections derived from the nominal Pythia sample (black triangles) and data (red circles) for jets with (a) |η| < 0.6, (b) 0.6 < |η| < 1.2, (c) 1.2 < |η| < 1.7, (d) 1.7 < |η| < 2.1 and (e) 2.1 < |η| < 2.8. Dierences between data and Monte Carlo simulation responses are shown at the bottom of each gure.
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0 0.5 1 1.5 2 2.5
Figure 5.16: Average jet response calculated using the truth jet as a function of η after applying the GS corrections derived from the nominal Pythia sample (black triangles) and data (red circles) for jets with (a) 80 < ptruthT < 110 GeV and (b) 260 < ptruthT < 310 GeV. Dierences between data and Monte Carlo simulation responses are shown at the bottom of each gure.
100 200 300 400 500 600 700 800
Response
100 200 300 400 500 600 700 800
Difference
-0.04
-0.020.020.040 MC10-Perugia2010 MC10-Herwig++
-0.020.020.040 MC10-Perugia2010 MC10-Herwig++
(b)
Figure 5.17: Average jet response calculated using the truth jet as a function of ptruthT after applying GS corrections derived from the nominal Pythia sample (black triangles) and data using the Atruth calculated using the nominal Pythia MC10 (red circles), the Perugia2010 tune (green triangles) and the Herwig++ sample (blue circles) for jets with (a) |η| < 0.6 and (b) 1.2 < |η| < 1.7.