First CDF Measurement of the Inclusive Jet Cross Section in Run II

Updated CDF Measurement of the Inclusive Jet Cross Section in Run II

We present an updated measurement of the inclusive jet E_T cross section in Run II based on an integrated luminosity of 177 pb^-1 of data collected in the period of Feb 2002 though July 2003 (runs 138815 through 166805). The data span the E_T range from 44 - 550 GeV, extending the upper limit by almost 150 GeV from Run I.

The first Run II inclusive jet measurements that were prsented at conferences in early 2003 was based in 85 pb^-1 of data. Since then we have a better understanding of the energy scale and have reduced the uncertainty from 5% to 3%. We also now have a dataset that exceeds our Run I sample and more than doubles the preliminary Run II results.

Blessed plots shown Spring 2003 conferences based on 85 pb^-1

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Events are collected using a three stage trigger.

At the Level 1 trigger events must satisfy the requirement that there is at least one trigger tower above a threshold of 5 or 10 GeV. At Level 2 the energy in the calorimeter is clustered and the trigger requirement is that there is at least one cluster above 15, 40, 60 or 90 GeV. At Level 3 jets are reconstructed using the JetClu cone algorithm (cone R = 0.7, z = 0) and events are required to have at least one Jet above the threshold of 20, 50, 70 or 100 GeV.

Prescales, shown in brackets, for the triggers are listed in the following table.

L1 L2 L3 ST5 (20) CL15 (12,25) J20 (1) CL40 (1) J50 (1) ST10 (1) CL60 (8) J70 (1) CL90 (1) J100 (1)

The measured Jet E_T is shown for the four jet triggers used in the analysis after accounting for the trigger prescales.

The measured inclusive jet E_T distribution is shown for the Run I and Run II data set.

The data in Run II extends the Run I results by about 150 GeV.

The lower edge of the E_T bins are selected so that the trigger is greater than 99% efficient.

The trigger efficiency is shown for the four jet triggers.

The measured inclusive jet E_T distribution for different regions of pseudorapidity.

The percent error on the corrected cross section is shown for the different sources of systematic error.

The energy scale uncertainty (estimated at 3%) is the dominant source of systematic error.

We can expect to understand the energy scale to the same level as in Run I, which was 1%.

The energy scale uncertainty is the dominant source of error and is shown as the dashed inner band compared to the total systematic error shown as the solid lines.

The individual sources of systematic error were added in quadrature to get the total.

The first preliminary measurement of the inclusive jet cross section is shown compared to the NLO QCD expectation determined using the CTEQ 6.1 parameterization of the parton density functions.

The variation in the cross section due to the systematic uncertainty is shown as the band. The two lines show the uncertainty in the cross section prediction due to the PDF.

The results are shown compared to the central value of the NLO QCD prediction using CTEQ6.1

The ratio of Data/Theory shown for CTEQ6.1. The error on the cross section resulting from the systematic uncertainty is shown as the band. The lines show the uncertainty arising from the PDF.

The ratio of Run II/Run I is shown compared to the QCD prediction using CTEQ6.1. The error on the cross section ratio resulting from the 3% energy scale uncertainty is shown as the band. The uncertainty due to the PDF is shown as the two lines.

The uncertainty on luminosity has not been included in the error band.

The data compared to a smooth function used in the unsmearing procedure.