cw_bw

• Some issues are known to exist.
• So although it is under the MIT license, please contact the author before use.

cw_bw is a lightweight simulation and fitting framework for investigating local baryon conservation (LBC) effects in heavy-ion collisions. It features a blast-wave event generator, with a standalone blast wave fitter on spectrum and elliptic flow.

Project Structure

cw_bw-main/
├── CMakeLists.txt
├── include/                    # Core C++ headers
├── src/                        # Core implementations
├── configs/                    # YAML configuration files
├── refdata/                    # Experimental data (ROOT/CSV)
├── scripts/
│   ├── BlastWaveFitter/        # Blast-wave spectrum fitting module (C++ ROOT)
│   ├── FittedData/             # Model vs data comparison (Python)
│   └── ScanPars/               # Parameter scan & plotting (Python)
└── LICENSE

Build Instructions

Requires C++17, ROOT, and CMake.

mkdir build && cd build
cmake ..
make -j

Usage

1. Generate Events

./bwgen -C 55 -n 100000 -c ../configs/default.yaml -o results.root

Arguments:

• -C: Centrality class (e.g., 15, 25, 35, 45, 55)
• -n: Number of events
• -c: YAML config file
• -o: Output ROOT file

2. Compare with Data

python3 scripts/FittedData/compare_model_alice_pre.py

3. Parameter Scan and Plot

python3 scripts/ScanPars/analysis.py

4. Blast-Wave Spectra Fit

The scripts/BlastWaveFitter/ directory contains a standalone ROOT macro for blast-wave fits:

root -l -b -q run_batch.C

This module fits identified particle spectra using the blast-wave model:

$$ \frac{1}{2\pi p_T}\frac{d^2N}{dp_T\,dy} \propto \int_0^R rdr \int_0^{2\pi} d\phi \, m_T I_0\left(\frac{p_T\sinh\rho}{T}\right) K_1\left(\frac{m_T\cosh\rho}{T}\right) $$

You can adjust flow parameters like T_kin, beta_T, and n inside BlastWaveFitter.C.

Reference Data

• ROOT files from HEPData
• CSV files from ALICE preliminary results

Config Examples

Available in configs/:

• default.yaml
• no_v2.yaml
• default_badboost.yaml

License

This project is licensed under the MIT License. See LICENSE for details.