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

102 CHAPTER 5: Estimating of the Jet Energy Scale Calibration Factorestimated jet energy corrections for the events with and without including pile-up aregiven.∆ε expl(%) ∆ε estl (%) ∆ε estl − ∆ε expl(%)nominal -9.38±0.25 -8.75±0.14 0.63±0.29pile-up -9.52±0.24 -8.68±0.13 0.84±0.27∆ε expb(%) ∆ε estb (%)∆ε estb− ∆ε expb(%)nominal -2.66±0.36 -2.81±0.20 -0.15±0.41pile-up -2.82±0.36 -3.30±0.20 -0.48±0.41Table 5.8: The expected and estimated residual jet energy corrections and the bias onthe estimations in the presence of pile-up events. The nominal refers to the situationwhen no pile-up is present.As it is seen from Table 5.8, the method of estimating the residual jet energy correctionsis stable with respect to adding the pile-up collisions. Obviously the expected aswell as the estimated corrections are affected by the pile-up collisions. If the pile-up iswell simulated, the bias should be stable. The estimated residual light and b jet energycorrections do not change much in the presence of the pile-up events. The estimatedlight jet energy correction changes from -8.75%, corresponding to the nominal value,to -8.68%, which is obtained when including pile-up events. Thus, the shift of 0.07%is considered as the systematic uncertainty on the estimated residual light jet energycorrection due to the pile-up effects. The deviation of the estimated b jet energy correctionfrom the nominal value corresponds to 0.49% which is taken as the systematicuncertainty on the estimated residual b jet energy correction due to the pile-up events.ISR/FSRWhen simulating physics events, various parameters are set to control the productionand decay products of the hard scattering interactions. Changing any of these parametersindividually, would yield to obtain a different topology of the event. Therefore,the sensitivity of the estimated results with respect to the changes of these parameters,has to be studied and the possible deviations are taken as the systematic uncertaintieson the final estimation. For example, the amount of ISR/FSR that are allowed to begenerated in the simulation procedure can affect the results. Two different sampleswith a smaller and larger amount of radiation compared to the nominal situation areprocessed. The estimated residual jet energy corrections are obtained for each of thesesamples which are given in Table 5.9. The estimated and expected results for light andb jet energy corrections are listed individually for the various samples.