TWiki> Main Web>TWikiUsers>AmnonHarel>AmnonHarelJetRatio>AmnonHarelDijetCentralityRatio>AmnonHarelEnsembleTestsWithFits (2010-09-21, AmnonHarel) EditAttachPDF

-- AmnonHarel - 18-Sep-2010
## Relevant hyperlinks

* Main page: AmnonHarelDijetCentralityRatio
## Introduction

Following the meeting with the ARC on Septemer 14th, added the option of doing sideband fits during the ensemble testing. This allows us to study several new questions: ## The fitted shift

## Consistency statistic for fitted models

## Technicalities

## Unsorted attachments

Contents:

- are the fitted statistical uncertainties correct?
- after all, this is a fit, which assumes each bin comes from a Gaussian ditribution

- what is the statistical significance (p-value) of the fitted shift?
- what are the consistency statistics and their p-values ifor models shifted to match data?

NLO with non perturbative corrections | |
---|---|

plot_shift.root | plot_shift_a.root |

- The distribution (with systematics, which widen it a bit) of the fitted statistical errors is close to a Gaussian( 0.0145, 0.0007 )
- the value in data (0.0133) is well within this distribution.
- but this shows that the fitted statistical uncertainties are significantly underestimated

- Not too interesting to derive similar plots for Pythia - the ensembles distributions will be similar, but the relevant |shift| is only 0.011

- currently the code does not allow testing this for the procedure used in the limit setting, i.e., no overlap between the fitted region and the signal region.
- that's fine - as this test is redundant, it's just an externally determined shift.

- can test the QCD models with the fit done on the entire range
- the systematics are a bit different than in the limit setting case - the full shape of the NPcorr and PDF uncertainties is used, rather than a flat offset appropriate to the normalization region. This is a new feature (20th September), and is important when testing the consistency statistic for shifted models, as the shift "takes away" the effect of the flat systematic variations.
- the behavior of the shift is quite expected - smaller statistical uncertainties can not explain the observed value, but the systematics can

- results for the consistency statistic are surprising - the consistency in the ensemble tests is bad (high C values), leading to a p-value of >95%.

- needed to add a new fitting method, with a custom likelihood whose inputs are two histograms. The usual technique is to fit a function to a histogram, but the functions are not available during ensemble testing as some of the systematic variations are done on the binned histograms derived from the functions.
- a few subtle changes needed throughout to accomodate this.
- the two fitting methods agree to 1-2% relative (since we quote up to two significant figures, both agree on the quoted numbers)

- plot_qcd_shift.root: plot_qcd_shift.root

I | Attachment | History | Action | Size | Date | Who | Comment |
---|---|---|---|---|---|---|---|

png | plot_qcd_shift.png | r2 r1 | manage | 25.8 K | 2010-09-21 - 18:05 | AmnonHarel | |

root | plot_qcd_shift.root | r1 | manage | 19.4 K | 2010-09-21 - 18:06 | AmnonHarel | |

png | plot_shift.png | r4 r3 r2 r1 | manage | 27.9 K | 2010-09-18 - 23:35 | AmnonHarel | |

root | plot_shift.root | r1 | manage | 19.4 K | 2010-09-18 - 23:36 | AmnonHarel | |

png | plot_shift_a.png | r4 r3 r2 r1 | manage | 17.5 K | 2010-09-18 - 23:35 | AmnonHarel | |

root | plot_shift_a.root | r2 r1 | manage | 15.3 K | 2010-09-18 - 23:36 | AmnonHarel |

Topic revision: r4 - 2010-09-21 - AmnonHarel

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