Reconstruction of di-tau mass using Machine Learning

Want to use models obtained from this repository in your analysis? Please go to DiTau_ML_mass. There you will have all the relevant information to use the models, without all the training stuff present here.

Installation

This repository

Fork the repository and clone it on your machine

mkdir -p <YOUR_DIRECTORY_NAME>
git clone <YOUR_FORKED_REPOSITORY> ./<YOUR_DIRECTORY_NAME>
cd <YOUR_DIRECTORY_NAME>
git remote add lucas git@github.com:lucastorterotot/DL_for_HTT_mass.git

Run the provided installation script to ensure setting variables properly:

./install

Event generation using Delphes

If you want to generate events with Delphes, follow the next steps.

• Delphes 3.4.2

mkdir -p $DL_for_HTT/Delphes && cd $DL_for_HTT/Delphes
wget http://cp3.irmp.ucl.ac.be/downloads/Delphes-3.4.2.tar.gz && tar -zxf Delphes-3.4.2.tar.gz
cd Delphes-3.4.2
make

• Pythia 8.235

mkdir -p $DL_for_HTT/Pythia8 && cd $DL_for_HTT/Pythia8
wget http://home.thep.lu.se/~torbjorn/pythia8/pythia8235.tgz && tar xzvf pythia8235.tgz
cd pythia8235 && ./configure --prefix=$(pwd)
make install
export PYTHIA8=$(pwd)
cd $DL_for_HTT/Delphes/Delphes-3.4.2/ && make HAS_PYTHIA8=true

Run a test

cd $DL_for_HTT/Delphes/Delphes-3.4.2
./DelphesPythia8 cards/delphes_card_CMS.tcl examples/Pythia8/configNoLHE.cmnd delphes_nolhe.root

HTT events generation

Using Delphes

Generate HTT events. It takes roughly 1 hour for 100000 events, try with 1000:

cd $DL_for_HTT/Event_generation_with_Delphes
gen_HTT_at_mass -m <mh in GeV> -N <number of events to generate>

Using FastSim

Instead of Delphes, one can use NanoAOD from CMS FastSim. See this repository.

Analyze the samples and get a .txt output table

To run the root to txt analysis on a file, do

HTT_Delphes_tree_analysis <FILE> <OUTPUT_NAME>

or, if FastSim was used,

HTT_FastSim_NanoAOD_tree_analysis <FILE> <OUTPUT_NAME>

Then you have a table in OUTPUT_NAME.txt that you can import in a python script using numpy, pandas, etc.

Now you would need the tf environment from conda on lyovis10:

conda activate tf

To merge the different .txt outputs (in principle one by root file, corresponding to one mass point and one amount of events) one can use the txt_merger script:

txt_merger -o <OUTPUT_NAME> <LIST_OF_INPUTS>

Make sure the columns are the same! To avoid typing all the files names, if for example you want to merge all Htt_XXX_NanoAODSIM.txt files where XXX is the Higgs mass into Htt_merged_NanoAODSIM.txt then you can do

txt_merger -o Htt_merged_NanoAODSIM.txt $(ls | grep Htt_.*_NanoAODSIM.txt | grep -ve Htt_merged_)

Once this is done, this txt file can be converted to hdf5 format as it uses less disk space:

txt_to_hdf5 Htt_merged_NanoAODSIM.txt Htt_merged_NanoAODSIM

Then you may delete root and txt files

find . -type f -iname Htt_\*_NanoAODSIM\*.{root,txt} -delete

Prepare data for model training

One has to define which data the NN will be trained on, which will be kept for testing, and so on. To do so, a dedicated script is provided:

analyzed_events_to_NN <input h5 file from previous step>

It will update the previous file with new information (train, valid or test event, weight of the event).

Options are available for this script:

• -m (min_mass), minimum mass point to consider;
• -M (max_mass), maximum mass point to consider;
• -t (train_frac), training fraction in the dataset;
• -v (valid_frac), validation fraction in the dataset, testing will be the remaining;
• -r (random_seed), random seed to use for splitting the dataset into train, valid and test parts;

Train ML models

Deep Neural Networks

You can run as a test

NN_trainer -L 1 -N 1 -o TEST -i no_METcov <input h5 file from previous step>

This will run a training on the events stored in the input h5 file from previous step with 1 (-L or --Nlayers) hidden layer containing 1 (-N or --Nneurons) neuron, so this would be quite quick (and not really a good model).

The used list of the model inputs will be the no_METcov list (-i or --model_inputs). Available inputs lists are stored in $DL_for_HTT/python/DL_for_HTT/common/model_inputs/.

In the working directory, a file named inputs_for_models_in_this_dir.py will make it possible to restore the list of inputs. You may create one directory for each group of models using a different list of inputs.

Output .json and .h5 files containing the NN structure will have a name containing TEST (-o or --output), the channel the NN has been trained on, the number of hidden layers and the base number of neurons per layer.

Other options are:

• -g or --gpu: the GPU unit to use. If several are available this makes it possible to give one GPU for two parallelized processes;
• -l or --loss: the loss function to use for training;
• -O or --optimizer: the optimizer to use for training, from tensorflow.keras.optimizers;
• -w or --w_init_mode: the weight initialisation mode;
• -m or --minmass: the minimum Higgs mass to consider for training;
• -M or --maxmass: the maximum Higgs mass to consider for training;
• -a or --activation: the activation function to use in the hidden layers;
• -c or --channels: the channels to train the constructed model on (one model obtained for each channel). It can be tt, mt, et, mm, em, ee, lt, ll, inclusive;
• -B or --batch_size: the batch size for training.

XGBoost regressor

You can run as a test

xgboost_trainer -d 1 -n 1 -o TEST -i no_METcov <input h5 file from previous step>

This will run a training on the events stored in the input h5 file from previous step with maximum 1 (-n or --n_estimators) of maximum 1 (-d or --max_depth) depth, so this would be quite quick (and not really a good model).

The used list of the model inputs will be the no_METcov list (-i or --model_inputs). Available inputs lists are stored in $DL_for_HTT/python/DL_for_HTT/common/model_inputs/.

In the working directory, a file named inputs_for_models_in_this_dir.py will make it possible to restore the list of inputs. You may create one directory for each group of models using a different list of inputs.

Output .json file containing the model structure will have a name containing TEST (-o or --output) and other information on the model.

Other options are:

• -e or --eta: the learning rate;
• -s or --early_stopping_rounds: the number of rounds to wait before stopping training once evaluation reaches a plateau;
• -E or --eval: the evaluation metric for the model (used for the early stopping);
• -g or --gamma: minimum loss reduction required to make a further partition on a leaf node of the tree;
• -w or --min_child_weight: minimum sum of instance weight (hessian) needed in a child;
• -j or --n_jobs: the number of parallel threads used to run xgboost;
• -O or --objective: the loss function to be minimized;
• -m or --minmass: the minimum Higgs mass to consider for training;
• -M or --maxmass: the maximum Higgs mass to consider for training;
• -c or --channels: the channels to train the constructed model on (one model obtained for each channel). It can be tt, mt, et, mm, em, ee, lt, ll, inclusive.

Test the models

A dedicated script, ml_plotter, makes it easy to get plots using the trained models:

ml_plotter --model <JSON FILE FOR MODEL> --events <H5 FILE CONTAINING EVENTS TO USE>

This will proceed all the possible plots for the provided model on the test subsample from the h5 file, on the inclusive channel (i.e. all at once). The plots to proceed can be reduced with a comma separated list given to the --plots option. The subsample to use (train, valid, test, all, any) can also be set with --subsample.