All Results

A systematic study on the cosmic ray antiproton ?ux

Su-Jie Lin; Xiao-Jun Bi; Jie Feng; Peng-Fei Yin; Zhao-Huan YuSubjects: Physics >> General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Recently the AMS-02 collaboration has published the measurement of the cosmic antiproton to proton ratio p?/p and the p? ?ux with a high precision up to ? 450 GeV. In this work, we perform a systematic analysis of the secondary antiproton ?ux generated by the cosmic ray interaction with the interstellar gas. The uncertainty of the prediction originates from the cosmic ray propagation process and the hadronic interaction models. Although the cosmic ray propagation parameters have been well controlled by the AMS-02 B/C ratio data for a speci?ed model, di?erent propagation models can not be discriminated by the B/C data. The p? ?ux is also calculated for several hadronic interaction models, which are generally adopted by the cosmic ray community. However, the results for di?erent hadronic models do not converge. We ?nd the EPOS LHC model, which seems to ?t the collider data very well, predicts a slightly lower p?/p ratio than the AMS-02 data at the high energy end. Finally we derive the constraints on the dark matter annihilation cross section from the AMS-02 p?/p ratio for di?erent propagation and hadronic interaction models. |

The 750 GeV diphoton excess at the LHC and dark matter constraints

Xiao-Jun Bi; Qian-Fei Xiang; Peng-Fei Yin; Zhao-Huan YuSubjects: Physics >> Nuclear Physics

The recent reported 750 GeV diphoton excess at the 13 TeV LHC is explained in the framework of effective field theory assuming the diphoton resonance is a scalar (pseudoscalar) particle. It is found that the large production rate and the broad width of this resonance are hard to simultaneously explain if only visible final states are considered. Therefore an invisible decay channel to dark matter (DM) is strongly favored by the diphoton excess with a broad width, given a large coupling of the new scalar to DM. We set constraints on the parameter space in this scenario using the results from LHC Run 1, DM relic density, and DM direct and indirect detection experiments. We find that the DM searches can exclude a large portion of the parameter regions accounting for the diphoton excess with a broad width. |

Subjects: Physics >> Nuclear Physics

We study the collider phenomenology of the electroweak phase transition and electroweak baryogenesis in the framework of the effective field theory. Our study shows that the effective theory using the dimension-6 operators can enforce strong first order phase transition and provide sizable CP violation to realize a successful electroweak baryogenesis. Such dimension-6 operators can induce interesting Higgs phenomenology that can be verified at colliders such as the LHC and the planning CEPC. We then demonstrate that this effective theory can originate from vector-like quarks and the triplet Higgs. |

Perturbativity Limits for Scalar Minimal Dark Matter with Yukawa Interactions: Septuplet

Chengfeng Cai; Ze-Min Huang; Zhaofeng Kang; Zhao-Huan Yu; Hong-Hao ZhangSubjects: Physics >> Nuclear Physics

The candidate of minimal dark matter (MDM) is limited if one demands perturbativity up to a very high scale, and it was believed that the MDM model with a real scalar septuplet could keep perturbative up to the Planck or GUT scale. In this work we point out that it is not true after taking into account the running of the quartic self-couplings of the scalar septuplet. For the septuplet mass around?10?TeV, which is suggested by the observed dark matter relic abundance, these couplings would hit the Landau pole at a scale??108?109?GeV, much lower than the Planck scale. We attempt to push up the Landau pole scale as high as possible by proposing an extension with extra Yukawa interactions of the septuplet. We find that in principle the Landau pole could be deferred to a scale of??1014?GeV if one could tolerate a serious fine-tuning of the initial condition of the Yukawa coupling. Moreover, if the MDM particle mass could be relaxed to??108?GeV, which would need some nonthermal production mechanisms to give a correct relic abundance, the Landau pole scale could be pushed up above the Planck scale. |

Implications for dark matter annihilation from the AMS-02 $\barp/p$ ratio

Su-Jie Lin; Xiao-Jun Bi; Peng-Fei Yin; Zhao-Huan YuSubjects: Physics >> Nuclear Physics

The AMS-02 collaboration has just released the cosmic antiproton to proton ratio?p?/p?with a high precision up to??450?GeV. In this work, we calculate the secondary antiprotons generated by cosmic ray interactions with the interstellar medium taking into account the uncertainties from the cosmic ray propagation. The?p?/p?ratio predicted by these processes shows some tension with the AMS-02 data in some regions of propagation parameters, but the excess is not significant. We then try to derive upper bounds on the dark matter annihilation cross section from the?p?/p?data or signal regions favored by the data. It is shown that the constraint derived by the AMS-02 data is similar to that from Fermi-LAT observations of dwarf galaxies. The signal region for dark matter is usually required?mχ?O(10)?TeV and?$\left<\sigma v\right>\sim\mathcal{O}(10^{-23})~\cm^3~\sec^{-1}$. |

Searches for dark matter signals in simplified models at future hadron colliders

Qian-Fei Xiang; Xiao-Jun Bi; Peng-Fei Yin; Zhao-Huan YuSubjects: Physics >> Nuclear Physics

We study the prospect of dark matter (DM) searches in the monojet channel at future?pp?colliders with center-of-mass energies of 33, 50, and 100~TeV. We consider a class of simplified models in which a vector boson connecting DM particles to quarks is introduced. Comparing with studies in the effective field theory, the present framework gives more reasonable production rates and kinematics of the DM signatures. We estimate the sensitivities of future colliders with an integrated luminosity of 3?ab?1?to the DM-induced monojet signature and show the parameter space that can be explored. The constraints from direct and indirect DM detection experiments are compared with the future collider sensitivities. We find that the future collider detection will be much more sensitive than the indirect detection for the vector interaction, and have better sensitivities than those of the direct detection by several orders of magnitude for the axial vector interaction. |

Searching for Singlino-Higgsino Dark Matter in the NMSSM

Qian-Fei Xiang; Xiao-Jun Bi; Peng-Fei Yin; Zhao-Huan YuSubjects: Physics >> Nuclear Physics

We study a simplified scenario in the next-to-minimal supersymmetric standard model with a split electroweak spectrum, in which only the singlino and higgsinos are light and other superpartners are decoupled. Serving as a dark matter candidate, a singlino-dominated neutralino?χ~01?should have either resonant annihilation effects or sizable higgsino components to satisfy the observed relic abundance. The sensitivities of LHC searches and dark matter detection experiments are investigated. With an integrated luminosity of?30(300)fb?1,?$3l + \missET$?and?$2l + \missET$?searches at the 13 (14) TeV LHC are expected to reach up to?$m_{\chia}\sim 150 (270) \mathrm{GeV}$?and?mχ~02,χ~±1?320(500)GeV. Near future dark matter direct and indirect detection experiments can cover some parameter regions where collider searches lose their sensitivities. |

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