arXiv subjects

Wei Chao

Publications and source records attributed to Wei Chao.

At least 55 records · Page 3Linked to original sources

arXiv2019

Indirect detection imprint of leptophilic dark matter

In this paper we revisit constraints on the leptophilic dark matter (DM) arising from the DM indirect detection experiments. Interactions between the charged leptons and the scalar-type, Dirac-type or vector-type DM are written in terms of effective operators. After classifying all interactions that may give non-zero signals in indirect detections, we study constraints on the parameter space of these effective interactions from the latest results of AMS-02, Planck, Fermi-LAT and H.E.S.S., as well as the observed relic abundance. Main results are summarized in the Table. I. It shows that the $τ$-flavored DM is almost excluded by the DM indirect detection results in some scenario.

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arXiv2019

Direct Detections of Dark Matter in the Presence of Non-standard Neutrino Interactions

In this paper we investigate impacts of non-standard neutrino interactions (NSIs) to the limitations on the discovery potential of dark matter in direct detection experiments. New neutrino floors are derived taking into account current upper bounds on the effective couplings of various NSIs. Our study shows that the neutrino floors of the standard model neutral current interactions can be significantly changed in the presence of vector-current NSI and scalar-current NSI, and the neutrino floors can be raised up to about ${\cal O}(20\%)$ in the presence of pseudo-scalar-current NSI, and there are almost no impacts to the neutrino floors from the axial-vector NSI and the tensor NSI. We suggest combining the dark matter direct detection experiments with the coherent elastic neutrino nucleus scattering experiments to hunt for new physics behind the signal of nuclear recoil in the future.

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arXiv2019

Direct detections of Majorana dark matter in vector portal

In this paper we investigate the direct detections of Majorana dark matter (MDM) in vector portal. Taking into account that the tree-level scattering cross sections in these models are either dark matter velocity suppressed or spin-dependent, we calculate radiative corrections to the spin-independent cross section in effective field theory approach. Wilson coefficients of effective MDM-quark interactions are calculated at the one-loop level, and the Wilson coefficient of the effective MDM-gluon interaction is derived at the two-loop level. Numerical results show that current constraints can rule out a narrow mass range of MDM when tree-level contributions are considered, and the spin-independent cross section from radiative corrections is reachable by the current direct detection technique for light MDM.

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arXiv2018

Scalar Electroweak Multiplet Dark Matter

We revisit the theory and phenomenology of scalar electroweak multiplet thermal dark matter. We derive the most general, renormalizable scalar potential, assuming the presence of the Standard Model Higgs doublet, $H$, and an electroweak multiplet $Φ$ of arbitrary SU(2$)_L$ rank and hypercharge, $Y$. We show that, in general, the $Φ$-$H$ Higgs portal interactions depend on three, rather than two independent couplings as has been previously considered in the literature. For the phenomenologically viable case of $Y=0$ multiplets, we focus on the septuplet and quintuplet cases, and consider the interplay of relic density and spin-independent direct detection cross section. We show that both the relic density and direct detection cross sections depend on a single linear combination of Higgs portal couplings, $λ_{\rm eff}$. For $λ_{\rm eff}\sim \mathcal{O}(1)$, present direct detection exclusion limits imply that the neutral component of a scalar electroweak multiplet would comprise a subdominant fraction of the observed DM relic density.

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arXiv2018

Hybrid Dark Matter

Dark matter can be produced in the early universe via the freeze-in or freeze-out mechanisms. Both scenarios were investigated in references, but the production of dark matters via the combination of these two mechanisms are not addressed. In this paper we propose a hybrid dark matter model where dark matters have two components with one component produced thermally and the other one produced non-thermally. We present for the first time the analytical calculation for the relic abundance of the Higgs portal hybrid dark matter, then we investigate constraints on the parameter space of the model from dark matter direct and indirect detection experiments.

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arXiv2017

The electron-flavored Z'-portal dark matter and the DAMPE cosmic ray excess

The DAMPE experiment has recently reported strong indications for the existence of an excess of high-energy electrons and positrons. If interpreted in terms of the annihilation of dark matter, the DAMPE result restricts the dark matter mass and possible annihilation channels to a few case. In this paper we explain the DAMPE result with the electron-flavored $Z^\prime$-portal fermionic dark matter. We show that the Dirac dark matter scenario is promising to explain the excess via the process $\bar χχ\to\mathbf{Z}'\to \bar e e$. The reduced annihilation cross section is limited in a range of $10^{-26}\sim 10^{-24}~{\rm cm^3 s^{-1}}$ to interpret the excess.

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arXiv2017

Electron Flavored Dark Matter

In this paper we investigate the phenomenology of the electron flavored Dirac dark matter with two types of portal interactions. We analyze constraints from the electron magnetic moment anomaly, LHC searches of singly charged scalar, dark matter relic abundance as well as direct and indirect detections. Our study shows that the available parameter space is quite constrained, but there are parameter space that is compatible with the current data. We further show that the DAMPE cosmic ray electron excess, which indicates cosmic ray excess at around 1.5 TeV, can be interpreted as the annihilation of dark matter into electron positron pairs in this model.

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arXiv2017

Phenomenology of the gauge symmetry for right-handed fermions

In this paper we investigate the phenomenology of the U(1) gauge symmetry for right-handed fermions, where three right-handed neutrinos are introduced for anomalies cancellation. Constraints on the new gauge boson $Z_{\mathbf{R}}$ arising from $Z-Z^\prime$ mixing as well as the upper bound of $Z^\prime$ production cross section in di-lepton channel at the LHC are presented. We further study the neutrino mass generation and the phenomenology of $Z_{\mathbf{R}}$-portal dark matter in this model. The lightest right-handed neutrino can be the cold dark matter candidate stabilized by a $Z_2$ flavor symmetry. Our results show that active neutrino masses can be generated via the modified type-II seesaw mechanism; right-handed neutrino dark matter is available only for its mass at near the resonant regime of the SM Higgs and/or the new bosons; constraint from the dilepton search at the LHC is stronger than that from the $Z-Z^\prime$ mixing only for $g_\mathbf{R}<0.121$, where $g_\mathbf{R}$ is the new gauge coupling.

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arXiv2017

Gravitational Wave Imprint of New Symmetry Breaking

It is believed that there are extra fundamental gauge symmetries beyond these described by the Standard Model of particle physics. The scale of these new gauge symmetries are usually too high to be reachable by particle colliders. Considering that the phase transition (PT) relating to the spontaneous breaking of new gauge symmetries to the electroweak symmetry might be strongly first order, we propose in this paper taking the stochastic gravitational waves (GW) arising from this phase transition as an indirect way of detecting these new fundamental gauge symmetries. As an illustration, we explore the possibility of detecting the stochastic GW generated from the PT of $\mathbf{ B-L}$ in the space-based interferometer detectors. Out study shows that the GW energy spectrum is reachable by the LISA, BBO, Taiji and DECIGO experiments only for the case where the spontaneous breaking of $\mathbf{B-L}$ is triggered by at least two electroweak singlet scalars.

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arXiv2017

CP Violation at the Finite Temperature

In this letter we explore the spontaneous CP violation at the finite temperature. We show that the CP-violating phase $φ$ may only emerge around the time of the electroweak phase transition, and it can provide a scource for generating the matter-antimatter asymmetry of the universe via the electroweak baryogenesis mechanism (EWBG) if the domain wall relating to $\pm φ$ vacuums is collapsed by a small explicit $Z_2$-breaking term. No extra CP violation is needed! The spontaneous CP is restored after the electroweak phase transition, such that there is no constraint from the electric dipole moment (EDM) measurements. This scenario resolves the tension between the non-observation of EDMs in precision measurement experiments and the requirement of a large CP violation by the EWBG.

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arXiv2017

Gravitational Wave Signals of Electroweak Phase Transition Triggered by Dark Matter

We study in this work a scenario that the universe undergoes a two step phase transition with the first step happened to the dark matter sector and the second step being the transition between the dark matter and the electroweak vacuums, where the barrier between the two vacuums, that is necessary for a strongly first order electroweak phase transition (EWPT) as required by the electroweak baryogenesis mechanism, arises at the tree-level. We illustrate this idea by working with the standard model (SM) augmented by a scalar singlet dark matter and an extra scalar singlet which mixes with the SM Higgs boson. We study the conditions for such pattern of phase transition to occur and especially for the strongly first order EWPT to take place, as well as its compatibility with the basic requirements of a successful dark matter, such as observed relic density and constraints of direct detections. We further explore the discovery possibility of this pattern EWPT by searching for the gravitational waves generated during this process in spaced based interferometer, by showing a representative benchmark point of the parameter space that the generated gravitational waves fall within the sensitivity of eLISA, DECIGO and BBO.

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arXiv2016

Horava-Lifshitz Type Quantum Field Theory and Hierarchy Problem

We study the Lifshitz type extension of the standard model (SM) at UV, with dynamical critical exponent z=3. One loop radiative corrections to the Higgs mass in such a model is calculated. Our result shows that, the Hierarchy problem, which has initiated many excellent extension of the minimal SM, can be weakened in the z=3 Lifshitz type quantum field theory.

hep-th↗

arXiv2016

Tau flavored dark matter and its impact on tau Yukawa coupling

In this paper we preform a systematic study of the tau flavored dark matter model by introducing two kinds of mediators (a scalar doublet and a charged scalar singlet). The electromagnetic properties of the dark matter, as well as their implications in dark matter direct detections, are analyzed in detail. The model turns out contributing a significant radiative correction to the tau lepton mass, in addition to loosing the tension between the measured dark matter relic density and constraints of dark matter direct detections. The loop corrections can be ${\cal O}(10\%)$ of the total tau mass. Signal rates of the Higgs measurements from the LHC in the $h\toττ$ and $h\to γγ$ channels, relative to the Standard Model expectations, can be explained in this model.

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arXiv2016

Symmetries Behind the 750 GeV Diphoton Excess

A 750 GeV resonance has been observed at the Run 2 LHC in the diphoton channel. In this paper, we explain this resonance as a CP-even scalar, S, that triggers the spontaneous breaking of local $U(1)_B$ or $U(1)_{B+L}$ gauge symmetries. S couples to gluon and photon pairs at the one-loop level, where particles running in the loop are originally introduced to cancel anomalies. The gluon fusion is the dominate production channel of S at the LHC. The model automatically contains a scalar dark matter candidate, stabilized by the new gauge symmetry. Our study shows that both the observed production cross section at the LHC and the best fit decay width of S can be explained in this concrete model, without conflicting with any experimental data. Constraints on couplings of S are studied, which shows a negligible mixing with the standard model Higgs boson but sizable coupling with the dark matter.

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arXiv2016

Majorana Dark matter with B+L gauge symmetry

We present a new model that extends the Standard Model (SM) with the local B+L symmetry, and point out that the lightest new fermion $ζ$, introduced to cancel anomalies and stabilized automatically by the B+L symmetry, can serve as the cold dark matter candidate. We study constraints on the model from Higgs measurements, electroweak precision measurements as well as the relic density and direct detections of the dark matter. Numerical results reveal that the pseudo-vector coupling of $ζ$ with $Z$ and the Yukawa coupling with the SM Higgs are highly constrained by the latest results of LUX, while there are viable parameter space that could satisfy all the constraints and give testable predictions.

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arXiv2016

Neutrino Catalyzed Diphoton Excess

In this paper we explain the 750 GeV diphoton resonance observed at the run-2 LHC as a scalar singlet $S$, that plays a key rule in generating tiny but nonzero Majorana neutrino masses. The model contains four electroweak singlets: two leptoquarks, a singly charged scalar and a neutral scalar $S$. Majorana neutrino masses might be generated at the two-loop level as $S$ get nonzero vacuum expectation value. $S$ can be produced at the LHC through the gluon fusion and decays into diphoton at the one-loop level with charged scalars running in the loop. The model fits perfectly with a wide width of the resonance. Constraints on the model are investigated, which shows a negligible mixing between the resonance and the standard model Higgs boson.

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arXiv2016

Indirect Detection Imprint of a CP Violating Dark Sector

We introduce a simple scenario involving fermionic dark matter ($χ$) and singlet scalar mediators that may account for the Galactic Center GeV $γ$-ray excess while satisfying present direct detection constraints. CP-violation in the scalar potential leads to mixing between the Standard Model Higgs boson and the scalar singlet, resulting in three scalars $h_{1,2,3}$ of indefinite CP-transformation properties. This mixing enables s-wave $χ{\barχ}$ annihilation into di-scalar states, followed by decays into four fermion final states. The observed $γ$-ray spectrum can be fitted while respecting present direct detection bounds and Higgs boson properties for $m_χ = 60 \sim 80 $ GeV, and $m_{h_3} \sim m_χ$. Searches for the Higgs exotic decay channel $h_1 \to h_3 h_3$ at the 14 TeV LHC should be able to further probe the parameter region favored by the $γ$-ray excess.

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arXiv2016

Hiding Scalar Higgs Portal Dark Matter

We investigate a Higgs portal dark matter model by extending the Standard model (SM) with a complex singlet, $S=(s+ia )/\sqrt{2}$, where $a $ is a dark matter candidate and $S$ gets no vacuum expectation value but $s$ mixies with the SM Higgs via a trilinear interaction. We point out an interesting scenario, where only quartic coupling contributes to the dark matter relic abundance and there is no tree level contribution to the direct detection. Numerical analysis shows that the direction detection cross section, which arises at the one-loop level, is about $2\sim 5$ orders below the current LUX bound. Constraints from Higgs measurements as well as collider signatures of the model at the LHC are studied.

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