Measurement of the Jet Energy Scale in the CMS experiment ... - IIHE

CHAPTER 5: Estimating of the Jet Energy Scale Calibration Factor 105of the variation of the matching threshold is investigated by running the method ofestimating the residual jet energy corrections on both simulated samples with thevarious settings of the matching thresholds and the nominal sample which is simulatedwith the pre-defined setting of the matching threshold. The results of the estimatedand the expected residual jet energy corrections with different settings of the matchingthreshold are summarized in Table 5.11.∆ε expl(%) ∆ε estl(%) ∆ε estl− ∆ε expl(%)nominal -9.38±0.25 -8.75±0.14 0.63±0.29matching up -9.19±0.28 -9.31±0.16 -0.12±0.32matching down -9.74±0.30 -9.37±0.17 0.37±0.34∆ε expb(%) ∆ε estb(%)∆ε estb− ∆ε expb(%)nominal -2.66±0.36 -2.81±0.20 -0.15±0.41matching up -3.07±0.41 -2.77±0.24 0.30±0.47matching down -3.17±0.43 -2.57±0.25 0.60±0.50Table 5.11: The expected and estimated residual jet energy corrections and the biason the estimations for the samples with higher and lower threshold in the matchingprocedure.It is seen from the results shown in Table 5.11 that the effects of changing thematching threshold on the final estimated results are minor and the estimation followsthe expected value since the bias on the estimated results is compatible with zero.The systematical uncertainties that can be assigned due to the changes in the matchingthreshold can be evaluated as follows. The estimated light jet energy correctionchanges from -9.31%, corresponding to the sample with larger matching threshold, to-9.37%, which is obtained when considering the simulated sample with smaller valueof the matching threshold. Compared to the nominal value which is -8.75%, the maximumdeviation of the estimated light jet energy correction is taken as the systematicuncertainty due to the changes in the matching threshold, being 0.62%. In case ofb jets, the maximum deviation would reach to 0.24% which is quoted as the systematicuncertainty on the estimated b jet energy correction due to the variation of thematching threshold.Combined SystematicsThe various systematic uncertainties on the estimated results of light and b jet energycorrections are summarized in Table 5.12. The total systematical uncertainty is calculatedas the square root of the sum of the squared uncertainties from the diversesources which are considered in the table.