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

130 CHAPTER 6: ConclusionUnc.(∆ε l )(%)765Unc.(∆ε b )(%)10846324120 100 200 300 400 500 600 700 800 900 1000 -1Luminosity (pb )0 100 200 300 400 500 600 700 800 900 1000 -1Luminosity (pb )Figure 6.1: The absolute statistical (curved line) as well as the systematical (straightline) uncertainties on the (left) light and (right) b jet energy corrections as a functionof the luminosity. From some point onward the systematical uncertainties dominatethe statistical uncertainties.values on simulation, also this is a limit of the precision of ∆E.Although the method is able to estimate the jet energy corrections inclusively, ithas also the capability to provide a differential estimation of the jet energy corrections.When larger amounts of statistics are recorded, the jets can be categorized in termsof their kinematics, such as pseudorapidity η or transverse momentum p T . Then, thesame method can be applied on the events which populate a particular bin of thesekinematic variables and consequently the estimated results would be obtained for thatregion of the phase space. This yields to obtain a differential estimation of the jetenergy corrections. With 36pb −1 where a low number of events survived the selectioncuts, a differential estimation is not feasible. Using a higher amount of statistics of forexample 2fb −1 , there are sufficient events remaining in the various regions of the phasespace that makes the differential method applicable and would result in meaningfulestimations. More detailed information on this aspect can be found in [106].The calibration method explained in this thesis will help the search for new physicsphenomena at the LHC, because when jets are better calibrated, the kinematic topologyof the new physics events can be better reconstructed and differentiated from thebackgrounds. Moreover, since in almost all the analyses, the jet energy scale calibrationis the main source of systematical uncertainty, a precise determination of the energyof the jets would also reduce the uncertainties originating from the jet energy scalecalibration factors and makes it possible to perform precision tests even at hadroncolliders like the LHC.