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Small long exercise fixes #930

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Apr 4, 2024
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Small long exercise fixes #930

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6 changes: 3 additions & 3 deletions docs/part5/longexercise.md
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Expand Up @@ -72,7 +72,7 @@ combine -M [method] [datacard] [additional options...]

### A: Computing limits using the asymptotic approximation

As we are searching for a signal process that does not exist in the standard model, it's natural to set an upper limit on the cross section times branching fraction of the process (assuming our dataset does not contain a significant discovery of new physics). <span style="font-variant:small-caps;">Combine</span> has dedicated method for calculating upper limits. The most commonly used one is `AsymptoticLimits`, which implements the [CLs criterion](https://inspirehep.net/literature/599622) and uses the profile likelihood ratio as the test statistic. As the name implies, the test statistic distributions are determined analytically in the [asymptotic approximation](https://arxiv.org/abs/1007.1727), so there is no need for more time-intensive toy throwing and fitting. Try running the following command:
As we are searching for a signal process that does not exist in the standard model, it's natural to set an upper limit on the cross section times branching fraction of the process (assuming our dataset does not contain a significant discovery of new physics). <span style="font-variant:small-caps;">Combine</span> has dedicated methods for calculating upper limits. The most commonly used one is `AsymptoticLimits`, which implements the [CLs criterion](https://inspirehep.net/literature/599622) and uses the [modified profile likelihood ratio for upper limits](../../what_combine_does/statistical_tests/#limit-setting-using-the-likelihood-ratio) as the default test statistic. As the name implies, the test statistic distributions are determined analytically in the [asymptotic approximation](https://arxiv.org/abs/1007.1727), so there is no need for more time-intensive toy throwing and fitting. Try running the following command:

```shell
combine -M AsymptoticLimits datacard_part1.txt -n .part1A
Expand Down Expand Up @@ -127,10 +127,10 @@ Next plot the test statistic distributions stored in the output file:
python3 $CMSSW_BASE/src/HiggsAnalysis/CombinedLimit/test/plotTestStatCLs.py --input higgsCombine.part1B.HybridNew.mH120.root --poi r --val all --mass 120
```

This produces a new ROOT file `cls_qmu_distributions.root` containing the plots, to save them as pdf/png files run this small script and look at the resulting figures:
This produces a new ROOT file `test_stat_distributions.root` containing the plots, to save them as pdf/png files run this small script and look at the resulting figures:

```shell
python3 printTestStatPlots.py cls_qmu_distributions.root
python3 printTestStatPlots.py test_stat_distributions.root
```
### Advanced section: B: Asymptotic approximation limitations

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