The U-boson (with mass 10-100 MeV) from an extra U (1) symmetry plays an essential role both in the annihilations of light dark matter (LDM) and understanding the new physics beyond the standard model. Furthermore, in the LDM model, the light vector U -boson can be produced from the rare decays of the   meson, which provides a possibility of detecting the U -boson in the Lab.

Researchers at Institute of Modern Physics, Chinese Academy of Sciences (IMP) investigated the light neutral vector U -boson from decay of   based on the LDM model and a relativistic transport (ART) model.

The momentum spectra of the U-boson with mass 10–100 MeV were obtained. It shows that the shapes of U-boson’s momentum spectra distributions are practically independent of its mass distributions but sensitive to the emission angle. Furthermore, the decay channel  was considered and the energy spectra of positron from U -boson decays were first presented.

Moreover, the feasibility and rationality of searching the U -boson in the experiment at AGS energy were discussed, which will be conduced to search for the U -boson in experiments and understand the light dark-matter particles.

The work has been published in European Physics Letters 104, 11001 (2013).

Fig.1 The distributions of U-boson (with mass 10 and 100 MeV) momentum spectra from the  rare decay. (Image by IMP)

Fig. 2 The energy spectra of positron from  U -boson decays. (Image by IMP)