CDF Logo Search for New Particles Decaying to Z0+jets Exotics Logo

We present the results of a search for new physics that couples to Z0 bosons in conjunction with jets. We describe a method that uses data alone to predict the background from Standard Model Z0+jet events, which is the dominant background and is virtually indeterminable with Monte Carlo. This method can be similarly applied to other analyses requiring background predictions in multi-jet environments, as we show when cross-checking the method to predict the background from W+jets in tt production. We see no significant excess in the data above the background prediction, and set a limit using a 4th-generation quark model to quantify the acceptance.




Plots and Tables:

Fit to 3rd-highest jet ET jet distribution in Z+jet data.
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Background prediction compared to Z+jet data, logarithmic scale.
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Background prediction compared to Z+jet data, linear scale.
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Cross section limit vs. mass.
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Crude background estimates using Monte Carlo, solely for the purpose of understanding that Standard Model Z+jets is the dominant background.
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Using Standard Model Z Monte Carlo, an illustration that the Njet30 ≤ 2 and Njet30 ≥ 3 cuts separate the 3rd-highest jet ET distribution at ET = 30 GeV.
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Consistency check of extrapolation: the fit to 3rd-highest jet ET distribution in Standard Model Z Monte Carlo
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The fit to 3rd-highest jet ET distribution in W+jet data. The excess is consistent with tt production with a cross section of 9 ± 1 pb.
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Using Z+jet data, a comparison of the shapes of the jet ET distributions in the Njet30 = 1 and Njet30 = 2 bins.
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W+jet data in the Njet30 ≥ 3 bins, compared to the background prediction+tt JT shape.
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