Please note: The tool is not ready for use and is not a current recommendation of TauWG!

The Tau Fake Factor Tool is an effort to harmonize estimation of jets reconstructed as tau objects, born from the Fake Tau Task Force (FTTF). The tool calculates fake factors (FF) for jets that are misidentified as taus. This is achieved by identifying the fraction of fake tau jets initiated by quarks and interpolating FF between known FFs associated with Z+jets and multijet processes for bins of pT and number of prongs. Therefore, the tool provides FFs for Z+jets and multijet regions as well as MC templates for quark and gluon initated jets in order to conduct the fit for the quark fraction. The discriminating variable used for quark/gluon separation is the LCTopo jet width.

An alternate method of the tool is available for use, which finds the fraction of multijet-like events in a given sample. This is achieved by using Z+jets and multijet jet width distributions as templates for the fit. The fraction of multijet-like events is then used to find the weighted combination of Z+jets and multijet FF to estimate the FF in the region of interest.


The Tau Fake Factor Tool (TFFT) exists as a single executable in the Athena 21.2 framework. The nominal tool requires a specific directory structure to specify the region where FF is calculated. In order to accommodate full functionality, each directory (each region), should include pT and jet width distributions binned in supported pT bins. The tool will parse the directory structure and perform interpolation “on-the-fly”. The workflow of TFFT is shown in attachment below ("workflow").

Note, the FTTF has not provided recommendations for systematics at this time. The tool, subsequently, does not provide systematics.

TFFT’s single executable (named fakeTauTool) requires one argument with an option flag:

$ fakeTauTool \path\to\input\file.root debugFlag = false

The debugFlag is an option argument (set to “false” by default). When set to “true”, provides every available histogram used by the tool for every step (including pT re-weighting to the input sample and those provided by the tool) as well as stacked histograms showing the quark fraction fit result against the quark/gluon templates. When set to the default, “false”, the tool simply provides the quark fraction fit histograms and interpolated FF.

Required Input Structure

A specific directory naming structure of inputs to TFFT is required in order to match specifics about the region of interest with the appropriate interpolation region. An example is to interpolate FF with Z+jets and multijet regions with the same BDT working point as the sample of interest.

The naming scheme for directories are:


with the following options (* refers to currently available options):

SampleName Prong BDTWP WPpassORfail BDTScoreCut JvtCut TriggerPass
"Arbitrary" 1p* loose pass* bdt005* jvt0* trig0*
3p* medium* fail* bdt05 jvt1 trig1
SampleName is a user-defined identifier which can be any arbitrary alphanumeric sequence. Prong is the prongness of the sample (one or three prong). BDTWP is the BDT working point of interest. WPpassORfail is whether the sample is the BDT pass or fail region. BDTScoreCut corresponds to a BDT score cut in the sample. JvtCut is whether tau objects have a JVT cut applied or not. TriggerPass is whether the tau objects are trigger-matched to a tau trigger in the sample or not. As an example, consider a sample of interest which contains one prong tau objects that fail the medium BDT working point, with BDT score cut of 0.005 with no JVT cut and are not subjected to trigger-matching.
The directory should be named:
Each directory should contain histograms of pT and jet width. The histogram naming convention defines the pT bins for which the user wishes to interpolate FF.
The naming scheme for histograms is:
This implies each pT bin should have a pT and jet width histogram. The available bins are:
Min Max
20 30
30 40
40 60
60 90
90 150
150 999
Thus, if one was interested in interpolating FF in pT bins 20-30 and 30-40, the following histograms should be included inside the appropriate directory:

The included histograms must be binned in order for direct comparison to provided templates. pT bins must be “fine-binned” in intervals of 1 GeV, where jet width histograms should have 30 bins from 0-0.3.

For instance, given the 20-30 GeV pT bin:
• pT binning:

{20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30}

• jet width binning:

{0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15,
0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3}

Once the appropriate histograms are created and placed into the appropriate directory, the resulting ROOT file can be given directory to TFFT. The tool has the capability to handle as many different samples (directories) at once as desired.

Data Template Method

Usage of this method is identical to the description above, however, pT histograms are no longer required to be passed to the tool. Only jet width histograms are necessary for interpolation since pT re-weighting is neglected in the data-driven method. A diagram of the workflow is attached below ("workflow_data").

The executable in the data template option is utilized as:
$ fakeTauToolData \path\to\input\file.root debugFlag = false

Test Input

A sample file which can be used for testing the functionality of the tool is available. The sample file is a bin-by-bin 40/60 mixture of multijet/Z+jet interpolation regions with pT bins up to 150 GeV.

The file is located at /eos/user/j/jmuse/fakeToolInputs


Feel free to contact Joe Muse at with any questions/concerns/comments about TFFT.

-- JosephMMuse - 2019-10-18

Topic attachments
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PNGpng data_workflow.png r1 manage 91.3 K 2019-11-05 - 13:07 JosephMMuse  
PNGpng workflow.png r1 manage 183.3 K 2019-11-05 - 13:07 JosephMMuse  
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Topic revision: r4 - 2019-11-06 - JosephMMuse
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