Purpose Gamma rays are important messengers to explore the Universe. The High Energy Cosmic Radiation Detection (HERD) facility has been proposed for installation on China’s Space Station (CSS) around 2027, which will play a crucial role in spaceborne experiments. The gamma-ray measurement is one of the important goals for HERD. The electron-positron pair conversion is the primary principle for detecting gamma rays above a few hundred MeV. A highly efficient gamma-ray reconstruction algorithm based on this principle is the first step in gamma-ray measurement. Methods A cellular automaton-based vertex reconstruction algorithm for HERD in the energy range of 300 MeV to 15 GeV is proposed for cases where the tracker can separate the electron or positron track. Results This algorithm successfully reconstructs the tracks of the electron-positron pair in the Z-X and Z-Y planes, respectively. The reconstruction efficiency is above 95% for both the Z-X and Z-Y planes. The angle resolution is about <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$0.34^{\circ }$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0</mn> <mo>.</mo> <msup> <mn>34</mn> <mo>∘</mo> </msup> </mrow> </math></EquationSource> </InlineEquation> for both planes and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$0.53^{\circ }$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0</mn> <mo>.</mo> <msup> <mn>53</mn> <mo>∘</mo> </msup> </mrow> </math></EquationSource> </InlineEquation> for 3D at the energy of 1 GeV. Conclusion In this paper, a cellular-based gamma vertex reconstruction algorithm is developed for events when the tracks of the converted electron and positron are separable. This method can capture the characteristics of the conversion vertex and simultaneously rebuild the tracks of the electron-positron pair. By utilizing the Kalman filter and selecting the higher-energy track based on the smaller <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\chi ^2$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>χ</mi> <mn>2</mn> </msup> </math></EquationSource> </InlineEquation>, the angle resolution at 1 GeV is significantly improved.

Gamma-ray vertex reconstruction for HERD experiment

期刊论文
发表日期：

2026年2月28日

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Liankun Zou,
Zhicheng Tang,
Ming Xu,
Qiyun Li,
Zhaoyi Qu,
Quanyin Li,
Zuhao Li

摘要

Purpose

Gamma rays are important messengers to explore the Universe. The High Energy Cosmic Radiation Detection (HERD) facility has been proposed for installation on China’s Space Station (CSS) around 2027, which will play a crucial role in spaceborne experiments. The gamma-ray measurement is one of the important goals for HERD. The electron-positron pair conversion is the primary principle for detecting gamma rays above a few hundred MeV. A highly efficient gamma-ray reconstruction algorithm based on this principle is the first step in gamma-ray measurement.

Methods

A cellular automaton-based vertex reconstruction algorithm for HERD in the energy range of 300 MeV to 15 GeV is proposed for cases where the tracker can separate the electron or positron track.

Results

This algorithm successfully reconstructs the tracks of the electron-positron pair in the Z-X and Z-Y planes, respectively. The reconstruction efficiency is above 95% for both the Z-X and Z-Y planes. The angle resolution is about $0.34^{\circ }$ $0 . 34^{\circ}$ for both planes and $0.53^{\circ }$ $0 . 53^{\circ}$ for 3D at the energy of 1 GeV.

Conclusion

In this paper, a cellular-based gamma vertex reconstruction algorithm is developed for events when the tracks of the converted electron and positron are separable. This method can capture the characteristics of the conversion vertex and simultaneously rebuild the tracks of the electron-positron pair. By utilizing the Kalman filter and selecting the higher-energy track based on the smaller $\chi ^2$ $χ^{2}$ , the angle resolution at 1 GeV is significantly improved.