JetEtmissJetPerformanceforHighLuminosity

Introduction

Introduction

[Mean number of pile-up jets vs mean number of interactions] The mean number of pile-up jets within |η| < 2.1 that pass various cuts on the reconstructed LCW-scale jet pT, versus the mean number of pile-up interactions per bunch crossing (< μ >). A correction, dependent on the number of reconstructed primary vertices and <μ>, was applied to the jets in order to subtract the average pT offset induced by pile-up. A power law was used to extrapolate the pile-up jet multiplicity to <μ> = 150. Since these extrapolations are based on only two data points each, there is a very large uncertainty in the extrapolated pile-up jet multiplicity.

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[Mean number of pile-up jets vs mean number of interactions]

The mean number of pile-up jets within |η| < 2.1 that pass various cuts on the reconstructed LCW-scale jet pT, versus the mean number of pile-up interactions per bunch crossing (< μ >). In addition to applying the average offset correction, these jets were required to match hard-scatter track jets of pT > 5 GeV (track-jet confirmed), which rejects a large fraction of pile-up jets. A power law was used to extrapolate the pile-up jet multi plicity to <μ> = 150. Since these extrapolations are based on only two data points each, there is a very large uncertainty in the extrapolated pile-up jet multiplicity.

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[Pt cut vs pile-up jet multiplicity]

The minimum LCW-scale pT cut versus pile-up jet multiplicity extrapolated to <μ> = 150. The data points are fit using an inverse power law. If an analysis requires fewer than 10 % of events to contain one or more pile-up jets, then a minimum pT of approximately 45 GeV would be necessary in the absence of track-jet confirmation. By using track-jet confirmation, it is possible to lower the minimum pT to approximately 25 GeV.

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[Jet resolution vs pt]

The jet energy resolution (σ(pT)/pT) measured for anti-kt jets with R = 0.4 within |η|<0.8, versus the true jet pT, in the EM+JES calibration. The data points are fit with the function σ(pT)/pT = √(N^2 /pT^2+ S^2/pT + C^2), where N, S and C are the noise, stochastic and constant terms in the resolution. The resolution is measured for samples with different values of <μ>, the mean number of pile-up interactions per bunch crossing. The noise term increases with <μ> , while the fitted value for S is constant within errors and C is kept fixed to its value for <μ> = 0.

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[Noise term vs mu]

Noise term (N) of the jet energy resolution versus the mean number of pile-up interactions per bunch crossing (<μ>). N is obtained from the fits to the jet energy resolution measured on anti-kt jets of R = 0.4 within |η|<0.8 in the EM+JES calibration. The value of N is reduced by applying the jet areas correction. A linear fit is used to extrapolate the value of N to <μ> = 150, which is 14 GeV for the average offset and 8 GeV when the jet areas correction is applied.

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Major updates:
-- TancrediCarli - 19-Jul-2012

Responsible: TancrediCarli
Subject: public

Attachments

Topic attachments
I	Attachment	History	Action	Size	Date	Who
eps	EM4-NvsMu-Y0.eps	r1	manage	12.6 K	2012-07-19 - 22:09	TancrediCarli
png	EM4-NvsMu-Y0.png	r1	manage	16.4 K	2012-07-19 - 22:09	TancrediCarli
eps	EM4-RinMuBins-eta0.eps	r1	manage	19.4 K	2012-07-19 - 22:09	TancrediCarli
png	EM4-RinMuBins-eta0.png	r1	manage	21.9 K	2012-07-19 - 22:09	TancrediCarli
eps	meanTJCVsMu_ETA0.eps	r1	manage	16.5 K	2012-07-19 - 22:09	TancrediCarli
png	meanTJCVsMu_ETA0.png	r1	manage	19.4 K	2012-07-19 - 22:09	TancrediCarli
eps	meanVsMu_ETA0.eps	r1	manage	16.1 K	2012-07-19 - 22:09	TancrediCarli
png	meanVsMu_ETA0.png	r1	manage	19.0 K	2012-07-19 - 22:09	TancrediCarli
eps	ptMinVsMean_ETA0.eps	r1	manage	12.6 K	2012-07-19 - 22:09	TancrediCarli
png	ptMinVsMean_ETA0.png	r1	manage	18.3 K	2012-07-19 - 22:09	TancrediCarli

Topic revision: r3 - 2012-07-20 - SabrinaSacerdoti

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