Decoding the Origin of Dark Matter

We discuss the interplay between LHC signatures and the mechanism by which dark matter is generated in the early universe in supersymmetric theories. The LHC signatures of two of the major mechanisms for such generation of dark matter which are known to be the Stau Coannihilation (Stau-Co) region and annihilation on the Hyperbolic Branch (HB) are exhibited in detail. By analyzing the various LHC signatures, including multi leptons, hadronic jets, b-tagging, and missing transverse momentum, one can discriminate between the Stau-Co region and the HB region for the mSUGRA model. Interestingly, there are some regions of the parameter space which are beyond the current and near future reach of the dark matter direct detection experiments but will be accessible at the LHC, and vise versa.Comment: 4 pages, 5 figures, based on a talk presented at SUSY 09; Boston, 5-10 June, 200

Two-mediator dark matter models and cosmic electron excess

The cosmic electron energy spectrum recently observed by the DAMPE experiment exhibits two interesting features, including a break around 0.9 TeV and a sharp resonance near 1.4 TeV. In this analysis, we propose a dark matter explanation to both exotic features seen by DAMPE. In our model, dark matter annihilates in the galaxy via two different channels that lead to both a narrow resonance spectrum near 1.4 TeV and electron excess events over an extended energy range thus generating the break structure around TeV. The two annihilation channels are mediated by two gauge bosons that interact both with dark matter and with the standard model fermions. Dark matter annihilations through the s-channel process mediated by the heavier boson produce monoenergetic electron-positron pairs leading to the resonance excess. The lighter boson has a mass smaller than the dark matter such that they can be on-shell produced in dark matter annihilations in the galaxy; the lighter bosons in the final state subsequently decay to generate the extended excess events due to the smeared electron energy spectrum in this process. We further analyze constraints from various experiments, including HESS, Fermi, AMS, and LHC, to the parameter space of the model where both excess events can be accounted for. In order to interpret the two new features in the DAMPE data, dark matter annihilation cross sections in the current galaxy are typically much larger than the canonical thermal cross section needed for the correct dark matter relic abundance. This discrepancy, however, is remedied by the nonperturbative Sommerfeld enhancement because of the existence of a lighter mediator in the model.Comment: 23 pages, 21 figure

LHC searches for the CP-odd Higgs by the jet substructure analysis

The LHC searches for the CP-odd Higgs boson is studied (with masses from 300 GeV to 1 TeV) in the context of the general two-Higgs-doublet model. With the discovery of the 125 GeV Higgs boson at the LHC, we highlight one promising discovery channel of the hZ. This channel can become significant after the global signal fitting to the 125 GeV Higgs boson in the general two-Higgs-doublet model. It is particularly important in the scenario where two CP-even Higgs bosons in the two-Higgs-doublet model have the common mass of 125 GeV. Since the final states involve a Standard-Model-like Higgs boson, we apply the jet substructure analysis of the fat Higgs jet in order to eliminate the Standard Model background sufficiently. After performing the kinematic cuts, we present the LHC search sensitivities for the CP-odd Higgs boson with mass up to 1 TeV via this channel.Comment: 26 pages, 12 figures, submitted to Phys. Rev.