add readme.

LICENSE

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+MIT License
+
+Copyright (c) 2024 Quan-feng WU <[email protected]> and Xun-Jie Xu <[email protected]>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# Solar Axion Primakoff Production Flux
+
+The codes for calculating the solar axion Primakoff production flux.
+
+## Usages
+
+The `Python` module is provided in the directory of `./SolarAxionPrimakoffFlux`.
+Please refer to the `main.ipynb` and the paper of [arXiv:2402.16083](https://arxiv.org/abs/2402.16083) for the usages in details.
+
+## Citation
+
+If you use the codes in your research, please cite [arXiv:2402.16083](https://arxiv.org/abs/2402.16083) via (copied from [Inspire HEP](https://inspirehep.net/literature/2761730))
+```bibtex
+@article{Wu:2024fsf,
+    author = "Wu, Quan-feng and Xu, Xun-Jie",
+    title = "{A comprehensive calculation of the Primakoff process and the solar axion flux}",
+    eprint = "2402.16083",
+    archivePrefix = "arXiv",
+    primaryClass = "hep-ph",
+    month = "2",
+    year = "2024"
+}
+```
+
+## License
+
+Copyright (c) 2024 Quan-feng WU <[email protected]> and Xun-Jie Xu <[email protected]>
+
+Released under the MIT License.
+https://opensource.org/licenses/MIT

SolarAxionPrimakoffFlux/Primakoff.py

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+# Copyright (c) 2024 Quan-feng WU <[email protected]> and Xun-Jie Xu <[email protected]>
+# 
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
 from numpy import clip, exp, log, sqrt
 from numpy import pi as π