Search for Ultra-Relativistic Magnetic Monopoles with LHAASO-KM2A
Abstract
Ultra-relativistic magnetic monopoles traversing the atmosphere are expected to initiate extensive air showers characterized by a muon deficit and a compact lateral profile. Using 1438.81 live days of data from the LHAASO-KM2A array, we present a search for these cosmic particles within the Lorentz factor range of 105 to 107. A machine-learning classifier utilizing lateral shower shape observables from the electromagnetic detectors is deployed to separate the signal from the hadronic background. No statistical excess above the background expectation is observed, and upper limits at the 90\% confidence level are established on the isotropic monopole flux. The resulting upper limit is 2.6 × 10−16 cm−2 s−1 sr−1 at γ= 105 and reaches 8.8 × 10−19 cm−2 s−1 sr−1 at γ= 107, which improves upon the astrophysical Parker bound by over three orders of magnitude. This work establishes constraints on the monopole flux within a previously unconstrained velocity window.
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BibTeX
@misc{cao2026search,
title = {{Search for Ultra-Relativistic Magnetic Monopoles with LHAASO-KM2A}},
author = {Zhen Cao and F. Aharonian and Y. X. Bai and Y. W. Bao and D. Bastieri and X. J. Bi and Y. J. Bi and W. Bian and J. Blunier and A. V. Butkevich and C. M. Cai and W. Y. Cao and Zhe Cao and J. Chang and J. F. Chang and E. S. Chen and G. H. Chen and H. K. Chen and L. F. Chen and Liang Chen and Long Chen and M. J. Chen and M. L. Chen and Q. H. Chen and S. Chen and S. H. Chen and S. Z. Chen and T. L. Chen and X. B. Chen and X. J. Chen and X. P. Chen and Y. Chen and N. Cheng and Q. Y. Cheng and Y. D. Cheng and M. Y. Cui and S. W. Cui and X. H. Cui and Y. D. Cui and B. Z. Dai and H. L. Dai and L. X. Dai and Z. G. Dai and Danzengluobu and Y. X. Diao and A. J. Dong and K. K. Duan and X. D. Duan and J. H. Fan and Y. Z. Fan and J. Fang and J. H. Fang and K. Fang and C. F. Feng and H. Feng and L. Feng and S. H. Feng and X. T. Feng and Y. Feng and Y. L. Feng},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.30968},
eprint = {2610.30968},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.30968},
}
RIS
TY - UNPB
TI - Search for Ultra-Relativistic Magnetic Monopoles with LHAASO-KM2A
AU - Zhen Cao
AU - F. Aharonian
AU - Y. X. Bai
AU - Y. W. Bao
AU - D. Bastieri
AU - X. J. Bi
AU - Y. J. Bi
AU - W. Bian
AU - J. Blunier
AU - A. V. Butkevich
AU - C. M. Cai
AU - W. Y. Cao
AU - Zhe Cao
AU - J. Chang
AU - J. F. Chang
AU - E. S. Chen
AU - G. H. Chen
AU - H. K. Chen
AU - L. F. Chen
AU - Liang Chen
AU - Long Chen
AU - M. J. Chen
AU - M. L. Chen
AU - Q. H. Chen
AU - S. Chen
AU - S. H. Chen
AU - S. Z. Chen
AU - T. L. Chen
AU - X. B. Chen
AU - X. J. Chen
AU - X. P. Chen
AU - Y. Chen
AU - N. Cheng
AU - Q. Y. Cheng
AU - Y. D. Cheng
AU - M. Y. Cui
AU - S. W. Cui
AU - X. H. Cui
AU - Y. D. Cui
AU - B. Z. Dai
AU - H. L. Dai
AU - L. X. Dai
AU - Z. G. Dai
AU - Danzengluobu
AU - Y. X. Diao
AU - A. J. Dong
AU - K. K. Duan
AU - X. D. Duan
AU - J. H. Fan
AU - Y. Z. Fan
AU - J. Fang
AU - J. H. Fang
AU - K. Fang
AU - C. F. Feng
AU - H. Feng
AU - L. Feng
AU - S. H. Feng
AU - X. T. Feng
AU - Y. Feng
AU - Y. L. Feng
PY - 2026
DA - 2026/10/22
PB - arXiv
DO - 10.48550/arxiv.2610.30968
UR - https://arxiv.org/abs/2610.30968
AB - Ultra-relativistic magnetic monopoles traversing the atmosphere are expected to initiate extensive air showers characterized by a muon deficit and a compact lateral profile. Using 1438.81 live days of data from the LHAASO-KM2A array, we present a search for these cosmic particles within the Lorentz factor range of 10^5 to 10^7. A machine-learning classifier utilizing lateral shower shape observables from the electromagnetic detectors is deployed to separate the signal from the hadronic background. No statistical excess above the background expectation is observed, and upper limits at the 90\% confidence level are established on the isotropic monopole flux. The resulting upper limit is 2.6 × 10^−16 cm^−2 s^−1 sr^−1 at γ= 10^5 and reaches 8.8 × 10^−19 cm^−2 s^−1 sr^−1 at γ= 10^7, which improves upon the astrophysical Parker bound by over three orders of magnitude. This work establishes constraints on the monopole flux within a previously unconstrained velocity window.
ER -