[en] Dark matter signature can be observed via the cosmic ray (electron/positron, neutrino, gamma, etc), as well as at LHC and/or low energy colliders (e.g. BES). In this talk, I will review our recent several studies on these aspects. (author)

[en] In this paper, we calculate the relic abundance of the dark matter particles when they can annihilate into sterile neutrinos with the mass ≲100 GeV in a simple model. Unlike the usual standard calculations, the sterile neutrino may fall out of the thermal equilibrium with the thermal bath before the dark matter freezes out. In such a case, if the Yukawa coupling y_N between the Higgs and the sterile neutrino is small, this process gives rise to a larger Ω_DMh² so we need a larger coupling between the dark matter and the sterile neutrino for a correct relic abundance.

[en] In this paper, forward-backward asymmetry and differential cross section of top quark in flavor violating Z^' model up to O(α_s²α_X) at Tevatron are calculated. In order to account for the top observed large forward-backward asymmetry, the new coupling g_X among Z^' and quarks will be not much less than strong coupling constant g_s. After including the new higher order correction, the differential cross section can fit the data better than those only including the leading contributions from Z^', while the forward-backward asymmetry is still in agreement with the measurement.

[en] In this paper, we will discuss a specific case that the dark matter particles annihilate into right-handed neutrinos. We calculate the predicted gamma-ray excess from the galactic center and compare our results with the data from the Fermi-LAT. An approximately 10–60 GeV right-handed neutrino with heavier dark matter particle can perfectly explain the observed spectrum. The annihilation cross section 〈σv〉 falls within the range 0.5–4×10"−"2"6 cm"3/s, which is roughly compatible with the WIMP annihilation cross section.

[en] We calculate the O(α_ewm_t(b)²/m_W²) and O(α_ewm_t(b)⁴/m_W⁴) supersymmetric electroweak corrections to the cross section for charged Higgs boson production in association with a top quark at the Fermilab Tevatron and the CERN large hadron collider (LHC). These corrections arise from the quantum effects which are induced by potentially large Yukawa couplings from the Higgs sector and the chargino-top-quark- (bottom-quark-) bottom-squark (top-squark) couplings, neutralino-top-quark- (bottom-quark-) top-squark (bottom-squark) couplings and charged Higgs-boson-top-squark-bottom-squark couplings. They can decrease or increase the cross section depending on tan β but are not very sensitive to the mass of the charged Higgs boson for high tan β. At low tan β(=2) the corrections decrease the total cross sections significantly, exceeding -12% for m_H^± below 300 GeV at both the Tevatron and the LHC, but for m_H^±>300 GeV the corrections become very small at the LHC. For high tan β(=10,30) these corrections can decrease or increase the total cross sections, and the magnitude of the corrections are at most a few percent at both the Tevatron and the LHC. (c) 2000 The American Physical Society

[en] We reconsider the dimension-11 Planck scale, the physical scale of the eleventh dimension, the physical scale of the Calabi-Yau manifold and the coupling in the hidden sector in M-theory on S¹/Z₂. Also we discuss reasonable bounds on them. Considering the F-term of the dilaton and moduli SUSY breaking and choosing two representative points which correspond to the scalar quasi-massless scenario and the dilaton dominant SUSY breaking scenario, respectively, we analyze experimental constraints on the parameter space. The sparticle spectrum and some phenomenological predictions are also given. (orig.)

[en] There may be non-thermal cosmic rays during big-bang nucleosynthesis (BBN) epoch (dubbed as BBNCRs). This paper investigated whether such BBNCRs can be the origin of Lithium problem or not. It can be expected that BBNCRs flux will be small in order to keep the success of standard BBN (SBBN). With favorable assumptions on the BBNCR spectrum between 0.09–4 MeV, our numerical calculation showed that extra contributions from BBNCRs can account for the ⁷Li abundance successfully. However ⁶Li abundance is only lifted an order of magnitude, which is still much lower than the observed value. As the deuteron abundance is very sensitive to the spectrum choice of BBNCRs, the allowed parameter space for the spectrum is strictly constrained. We should emphasize that the acceleration mechanism for BBNCRs in the early universe is still an open question. For example, strong turbulent magnetic field is probably the solution to the problem. Whether such a mechanism can provide the required spectrum deserves further studies

[en] We study the exotic decay of the 125 GeV Higgs boson (h) into a pair of light spin-0 particles (φ) which subsequently decay and result in a 4b final state. This channel is well motivated in models with an extended Higgs sector. Instead of searching at the Large Hadron Collider (LHC) and the high luminosity LHC (HL-LHC) which are beset by large standard model (SM) backgrounds, we investigate this decay channel at the much cleaner Large Hadron Electron Collider (LHeC). With some simple selection cuts this channel becomes nearly free of background at this ep machine, in sharp contrast to the situation at the (HL-)LHC. With a parton level analysis we show that for the φ mass range [20,60] GeV, with 100 fb"-"1 luminosity the LHeC is generally capable of constraining C_4_b"2 ≡ κ_V"2 x Br(h → φφ) x Br"2(φ → b anti b) (κ_V denotes the hVV(V = W, Z) coupling strength relative to the SM value) to a few percent level (95% CLs). With 1 ab"-"1 luminosity C_4_b"2 at a few per mille level can be probed. These sensitivities are much better than the HL-LHC performance and demonstrate the important role expected to be played by the LHeC in probing exotic Higgs decay processes, in addition to the already proposed invisible Higgs decay channel. (orig.)

[en] Composite Higgs and neutral-naturalness models are popular scenarios in which the Higgs boson is a pseudo Nambu-Goldstone boson (PNGB), and naturalness problem is addressed by composite top partners. Since the standard model effective field theory (SMEFT) with dimension-six operators cannot fully retain the information of Higgs nonlinearity due to its PNGB nature, we systematically construct low energy Lagrangian in which the information of compositeness and Higgs nonlinearity are encoded in the form factors, the two-point functions in the top sector. We classify naturalness conditions in various scenarios, and first present these form factors in composite neutral naturalness models. After extracting out Higgs effective couplings from these form factors and performing the global fit, we find the value of Higgs top coupling could still be larger than the standard model one if the top quark is embedded in the higher dimensional representations. Also we find the impact of Higgs nonlinearity is enhanced by the large mass splitting between composite states. In this case, pattern of the correlation between the t$\stackrel{¯<!--\; ??\; -->}{t}$h and t$\stackrel{¯<!--\; ??\; -->}{t}$hh couplings is quite different for the linear and nonlinear Higgs descriptions.

[en] Boost factors of dark matter annihilation into antiprotons and electrons/positrons due to the clumpiness of dark matter distribution are studied in detail in this work, taking the Sommerfeld effect into account. It has been thought that the Sommerfeld effect, if exists, will be more remarkable in substructures because they are colder than the host halo, and may result in a larger boost factor. We give a full calculation of the boost factors based on the recent N-body simulations. Three typical cases of Sommerfeld effects, the non-resonant, moderately resonant and strongly resonant cases are considered. We find that for the non-resonant and moderately resonant cases the enhancement effects of substructures due to the Sommerfeld effect are very small ( ∼ O(1)) because of the saturation behavior of the Sommerfeld effect. For the strongly resonant case the boost factor is typically smaller than ∼ O(10). However, it is possible in some very extreme cases that DM distribution is adopted to give the maximal annihilation the boost factor can reach up to ∼ 1000. The variances of the boost factors due to different realizations of substructures distribution are also discussed in the work