The XENON IT excess of keV electron recoil events may be induced by the scattering of electrons and long-lived particles with an MeV mass and high speed.We consider a tangible model composed of two scalar MeV dark mat...The XENON IT excess of keV electron recoil events may be induced by the scattering of electrons and long-lived particles with an MeV mass and high speed.We consider a tangible model composed of two scalar MeV dark matter(DM) particles,S_(A) and S_(B),to interpret the XENON IT keV excess via boosted S_(B).A small mass splitting m_(S_(A))-m_(S_(B))>0 is introduced,and the boosted S_(B) can be produced using the dark annihilation process of S_(A)S_(A)^(■)→φ→S_(B)S_(B)^(■) via a resonant scalar φ.S_(B)-electron scattering is intermediated by a vector boson X.Although the constraints from Big Bang nucleosynthesis,cosmic microwave background(CMB),and low-energy experiments set the X-mediated S_(B)-electron scattering cross section to be≤10^(-35)cm^(2),the MeV scale DM with a resonance enhanced dark annihilation today can still provide sufficient boosted S_(B) and induce the XENON1 T keV excess.The relic density of S_(B) is significantly reduced by the s-wave process S_(B)S_(B)^(■)→XX,which is permitted by the constraints from CMB and 21-cm absorption.A very small relic fraction of S_(B) is compatible with the stringent bounds on un-boosted S_(B)-electron scattering in DM direct detection,and the S_(A)-electron scattering is also allowed.展开更多
基金supported by the National Natural Science Foundation of China (11975129,12035008)"the Fundamental Research Funds for the Central Universities",Nankai University (63196013)support from the Longshan academic talent research supporting program of SWUST(18LZX415)。
文摘The XENON IT excess of keV electron recoil events may be induced by the scattering of electrons and long-lived particles with an MeV mass and high speed.We consider a tangible model composed of two scalar MeV dark matter(DM) particles,S_(A) and S_(B),to interpret the XENON IT keV excess via boosted S_(B).A small mass splitting m_(S_(A))-m_(S_(B))>0 is introduced,and the boosted S_(B) can be produced using the dark annihilation process of S_(A)S_(A)^(■)→φ→S_(B)S_(B)^(■) via a resonant scalar φ.S_(B)-electron scattering is intermediated by a vector boson X.Although the constraints from Big Bang nucleosynthesis,cosmic microwave background(CMB),and low-energy experiments set the X-mediated S_(B)-electron scattering cross section to be≤10^(-35)cm^(2),the MeV scale DM with a resonance enhanced dark annihilation today can still provide sufficient boosted S_(B) and induce the XENON1 T keV excess.The relic density of S_(B) is significantly reduced by the s-wave process S_(B)S_(B)^(■)→XX,which is permitted by the constraints from CMB and 21-cm absorption.A very small relic fraction of S_(B) is compatible with the stringent bounds on un-boosted S_(B)-electron scattering in DM direct detection,and the S_(A)-electron scattering is also allowed.
