https://doi.org/10.1140/epjc/s10052-025-14290-y
Regular Article - Theoretical Physics
Are the new particles heavy or light in 
?
1
Department of Physics, Guangxi Normal University, 541004, Guilin, Guangxi, China
2
Guangxi Key Laboratory of Nuclear Physics and Technology, 541004, Guilin, Guangxi, China
3
School of Physics and Electrical Engineering, Anyang Normal University, 455000, Anyang, Henan, China
Received:
5
March
2025
Accepted:
6
May
2025
Published online:
20
May
2025
In this work, we study the 
, 
, and 
decays under three different new physics hypotheses: the heavy new particles, the light neutral vector particles, and the axion-like particles. We find that all three hypotheses can resolve the Belle-II excess, and they can be clearly distinguished by the longitudinal polarization fraction of 
. Furthermore, we discover that the longitudinal polarization fraction of 
can be used to distinguish the chirality of the effective operators.
© The Author(s) 2025
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