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
In contrast with B0-ˉB0, Bs-ˉBs mixing where the standard model（SM） contributions overwhelm that of the new physics beyond standard model（BSM）, a measured relatively large D0-ˉD0mixing where the SM contribution...In contrast with B0-ˉB0, Bs-ˉBs mixing where the standard model（SM） contributions overwhelm that of the new physics beyond standard model（BSM）, a measured relatively large D0-ˉD0mixing where the SM contribution is negligible, definitely implies the existence of the new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the decay mode D0→μ＋μ-could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of the new physics BSM in the leptonic decays of D0. Concretely we discuss the contributions of unparticle or an extra gauge boson Z while imposing the constraints set by fitting the D0-ˉD0mixing data. We find that the long-distance SM effects for D0→lˉl still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as D0→μ±e, the new physics contribution would be significant.展开更多
The long-standing Galactic center gamma-ray excess could be explained by GeV dark matter(DM)annihilation,but the DM interpretation seems to conflict with recent joint limits from different astronomical scale observati...The long-standing Galactic center gamma-ray excess could be explained by GeV dark matter(DM)annihilation,but the DM interpretation seems to conflict with recent joint limits from different astronomical scale observations such as dwarf spheroidal galaxies,the Milky Way halo,and galaxy groups/clusters.Motivated by ^(8)Be and ^(4)He anomalous transitions with possible new interactions mediated by a vector boson X,we consider a small fraction of DM mainly annihilating into a pair of on-shell vector bosons followed by in this paper.The Galactic center gamma-ray excess is explained by this DM cascade annihilation.The gamma rays are mainly from inverse Compton scattering emission,and the DM cascade annihilation could be compatible with joint astrophysical limits and meanwhile be allowed by AMS-02 positron observation.The direct detection of this model is also discussed.展开更多
Supersymmetry （SUSY） may be one of the most favored extensions of the Standard Model （SM）, but so far at the LHC no evidence of SUSY particles has been observed. An obvious question is whether they have already em...Supersymmetry （SUSY） may be one of the most favored extensions of the Standard Model （SM）, but so far at the LHC no evidence of SUSY particles has been observed. An obvious question is whether they have already emerged but escaped our detection, or whether they do not exist at all. We propose that the future ILC may provide sufficient energy and luminosity to produce SUSY particles as long as they are not too heavy. Superflavor symmetry associates production rates of SUSY mesinos with those of regular mesons, because both contain a heavy constituent and a light one. In this work, we estimate the production rate of SUSY mesinos near their production threshold and compare it with BB production. Our analysis indicates that if SUSY mesinos with masses below √s/2 （√s is the ILC energy） exist, they could be observed at the future ILC or even the proposed CEPC in China.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.
基金Supported by National Natural Science Foundation of China(11375128)
文摘In contrast with B0-ˉB0, Bs-ˉBs mixing where the standard model（SM） contributions overwhelm that of the new physics beyond standard model（BSM）, a measured relatively large D0-ˉD0mixing where the SM contribution is negligible, definitely implies the existence of the new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the decay mode D0→μ＋μ-could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of the new physics BSM in the leptonic decays of D0. Concretely we discuss the contributions of unparticle or an extra gauge boson Z while imposing the constraints set by fitting the D0-ˉD0mixing data. We find that the long-distance SM effects for D0→lˉl still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as D0→μ±e, the new physics contribution would be significant.
基金The work of T.Li was Supported by the the National Natural Science Foundation of China(11975129,12035008)“the Fundamental Research Funds for the Central Universities”,Nankai University(63196013)L.-B.Jia was Supported by the Longshan academic talent research supporting program of SWUST(18LZX415)。
文摘The long-standing Galactic center gamma-ray excess could be explained by GeV dark matter(DM)annihilation,but the DM interpretation seems to conflict with recent joint limits from different astronomical scale observations such as dwarf spheroidal galaxies,the Milky Way halo,and galaxy groups/clusters.Motivated by ^(8)Be and ^(4)He anomalous transitions with possible new interactions mediated by a vector boson X,we consider a small fraction of DM mainly annihilating into a pair of on-shell vector bosons followed by in this paper.The Galactic center gamma-ray excess is explained by this DM cascade annihilation.The gamma rays are mainly from inverse Compton scattering emission,and the DM cascade annihilation could be compatible with joint astrophysical limits and meanwhile be allowed by AMS-02 positron observation.The direct detection of this model is also discussed.
基金Supported by National Natural Science Foundation of China(11075079,11135009,11005061)
文摘Supersymmetry （SUSY） may be one of the most favored extensions of the Standard Model （SM）, but so far at the LHC no evidence of SUSY particles has been observed. An obvious question is whether they have already emerged but escaped our detection, or whether they do not exist at all. We propose that the future ILC may provide sufficient energy and luminosity to produce SUSY particles as long as they are not too heavy. Superflavor symmetry associates production rates of SUSY mesinos with those of regular mesons, because both contain a heavy constituent and a light one. In this work, we estimate the production rate of SUSY mesinos near their production threshold and compare it with BB production. Our analysis indicates that if SUSY mesinos with masses below √s/2 （√s is the ILC energy） exist, they could be observed at the future ILC or even the proposed CEPC in China.
