arXiv subjects

Qian-Fei Xiang

Publications and source records attributed to Qian-Fei Xiang.

17 recordsLinked to original sources

arXiv2023

Soft Scattering Evaporation of Dark Matter Subhalos by Inner Galactic Gases

The large gap between a galactic dark matter subhalo's velocity and its own gravitational binding velocity creates the situation that small subhalos can be evaporated before dark matter thermalize with baryons due to the low binding velocity. In case dark matter acquires an electromagnetic dipole moment, the survival of low-mass subhalos requires stringent limits on the photon-mediated soft scattering. The current stringent direct detection limits indicate for a small dipole moment, which lets DM decouple early and allows small subhalos to form. We calculate the DM kinetic decoupling temperature in the Early Universe and evaluate the smallest protohalo mass. In the late Universe, low-mass subhalos can be evaporated via soft collision by ionized gas and accelerated cosmic rays. We calculate the subhalos evaporation rate and show that subhalos lighter than $10^{-5}M_{\odot}$ in the gaseous inner galactic region are subject to evaporation via dark matter's effective electric and magnetic dipole moments below current direct detection limits, which potentially affects the low-mass subhalos distribution in the galactic center.

astro-ph.CO↗

arXiv2021

Exploring Fermionic Multiplet Dark Matter through Precision Measurements at the CEPC

New physics could be explored through loop effects by the precision measurements at the Circular Electron Positron Collider due to its clean collision environment and high luminosity. In this work, we focus on two dark matter models that involve additional electroweak fermionic multiplets. We calculate their one-loop corrections to five processes, i.e. $e^+e^- \to μ^+μ^-, ~Zh, ~ZZ, ~W^+W^-$, and $Zγ$, and investigate the corresponding signatures at CEPC with the projected sensitivity. We find that the detectable parameter regions of these processes are complementary. The combined analysis shows that the mass of dark matter $m_{χ^0_1}$ in these two models can be probed up to $ \sim 150~\mathrm{GeV}$ and $\sim 450$ GeV at a 95\% confidence level, respectively.

hep-ph↗

arXiv2020

Dark Matter Search at Colliders and Neutrino Floor

The sensitivity of direct detection of dark matter (DM) approaches the so-called neutrino floor below which it is hard to disentangle the DM candidate from the background neutrino. In this work we consider the scenario that no DM signals are reported in various DM direct detection experiments and explore whether the collider searches could probe the DM under the neutrino floor. We adopt several simplified models in which the DM candidate couples only to electroweak gauge bosons or leptons in the standard model through high dimensional operators. After including the RGE running effect we investigate constraints from direct detection, indirect detection and collider searches. The collider search can probe a light DM below neutrino floor. Especially, for the effective interaction of $\barχχB_{μν}B^{μν}$, current data of the mono-photon channel at the 13 TeV LHC has already covered entire parameter space of the neutrino floor.

hep-ph↗

arXiv2020

Exploring for sub-MeV Boosted Dark Matter from Xenon Electron Direct Detection

Direct detection experiments turn to lose sensitivity of searching for a sub-MeV light dark matter candidate due to the threshold of recoil energy. However, such light dark matter particles can be accelerated by energetic cosmic-rays such that they can be detected with existing detectors. We derive the constraints on the scattering of a boosted light dark matter and electron from the XENON100/1T experiment. We illustrate that the energy dependence of the cross section plays a crucial role in improving both the detection sensitivity and also the complementarity of direct detection and other experiments.

hep-ph↗

arXiv2020

Isospin-Violating Dark Matter in the $U(1)'$ Model with $E_6$ Origin

We propose a $U(1)'$ model from $E_6$ which has an isospin-violation dark matter. By choosing a proper linear combination of two extra $U(1)$ gauge symmetries in $E_6$, it is natural to realize the ratio $f_n/f_p=-0.7$ so as to maximally relax the constraints from the Xenon based direct detection experiments. We study the sensitivities of the dark matter direct and indirect detection experiments, and identify the parameter spaces that can give the observed relic density. We also study the sensitivities of the future colliders with center mass energy $\sqrt{s}$= 33/50/100 TeV, and compare the different detection methods. We show that in some parameter spaces the future colliders can give much stronger limits.

hep-ph↗

arXiv2018

Hexapod Coloron at the LHC

Instead of the usual dijet decay, the coloron may mainly decay into its own "Higgs bosons", which subsequently decay into many jets. This is a general feature of the renormalizable coloron model, where the corresponding "Higgs bosons" are a color-octet $Θ$ and a color-singlet $ϕ_I$. In this paper, we perform a detailed collider study for the signature of $pp \rightarrow G' \rightarrow (Θ\rightarrow gg) (ϕ_I \rightarrow gg q\bar{q})$ with the coloron $G'$ as a six-jet resonance. For a light $ϕ_I$ below around 0.5 TeV, it may be boosted and behave as a four-prong fat jet. We also develop a jet-substructure-based search strategy to cover this boosted $ϕ_I$ case. Independent of whether $ϕ_I$ is boosted or not, the 13 TeV LHC with 100 fb$^{-1}$ has great discovery potential for a coloron with the mass sensitivity up to 5 TeV.

hep-ph↗

arXiv2018

Exploring Fermionic Dark Matter via Higgs Boson Precision Measurements at the Circular Electron Positron Collider

We study the impact of fermionic dark matter (DM) on projected Higgs precision measurements at the Circular Electron Positron Collider (CEPC), including the one-loop effects on the $e^+e^-\to Zh$ cross section and the Higgs boson diphoton decay, as well as the tree-level effects on the Higgs boson invisible decay. As illuminating examples, we discuss two UV-complete DM models, whose dark sector contains electroweak multiplets that interact with the Higgs boson via Yukawa couplings. The CEPC sensitivity to these models and current constraints from DM detection and collider experiments are investigated. We find that there exist some parameter regions where the Higgs measurements at the CEPC will be complementary to current DM searches.

hep-ph↗

arXiv2018

Exploring triplet-quadruplet fermionic dark matter at the LHC and future colliders

We study the signatures of the triplet-quadruplet dark matter model at the LHC and future colliders, including the 100 TeV Super Proton-Proton Collider and the 240 GeV Circular Electron Positron Collider. The dark sector in this model contains one fermionic electroweak triplet and two fermionic quadruplets, which have two kinds of Yukawa couplings to the Higgs doublet. Electroweak production signals of the dark sector fermions in the $\text{monojet}+/\!\!\!\!E_\mathrm{T}$, disappearing track, and $\text{multilepton}+/\!\!\!\!E_\mathrm{T}$ channels at the LHC and the Super Proton-Proton Collider are investigated. Moreover, we study the loop effects of this model on the Circular Electron Positron Collider precision measurements of $e^+e^-\to Zh$ and $h\toγγ$. We find that most of the parameter regions allowed by the observed dark matter relic density will be well explored by such direct and indirect searches at future colliders.

hep-ph↗

arXiv2017

Status of Natural Supersymmetry from the GmSUGRA in Light of the current LHC Run-2 and LUX data

We study natural supersymmetry in the Generalized Minimal Supergravity (GmSUGRA). For the parameter space with low energy electroweak fine-tuning measures less than 50, we are left with only the $Z$-pole, Higgs-pole and Higgsino LSP scenarios for dark matter (DM). We perform the focused scans for such parameter space and find that it satisfies various phenomenological constraints and is compatible with the current direct detection bound on neutralino DM reported by the LUX experiment. Such parameter space also has solutions with correct DM relic density besides the solutions with DM relic density smaller or larger than 5$σ$ WMAP9 bounds. We present five benchmark points as examples. In these benchmark points, gluino and the first two generations of squarks are heavier than 2 TeV, stop $\tilde t_{1,2}$ are in the mass range $[1,2]$ TeV, while sleptons are lighter than 1 TeV. Some part of the parameter space can explain the muon anomalous magnetic moment within 3$σ$ as well. We also perform the collider study of such solutions by implementing and comparing with relevant studies done by the ATLAS and CMS Collaborations. We find that the points with Higgsino dominant $\tildeχ_2^0/\tilde{χ_1}^\pm$ mass up to $300$ GeV are excluded in $Z$-pole scenario while for Higgs-pole scenario, the points with $\tildeχ_2^0$ mass up to $460$ GeV are excluded. We also notice that the Higgsino LSP points in our present scans are beyond the reach of present LHC searches. Next, we show that for both the $Z$-pole and Higgs-pole scenarios, the points with electroweak fine-tuning measure around 20 do still survive.

hep-ph↗

arXiv2017

A dark matter model that reconciles tensions between the cosmic-ray $e^\pm$ excess and the gamma-ray and CMB constraints

The cosmic-ray (CR) $e^\pm$ excess observed by AMS-02 can be explained by dark matter (DM) annihilation. However, the DM explanation requires a large annihilation cross section which is strongly disfavored by other observations, such as the Fermi-LAT gamma-ray observation of dwarf galaxies and the Planck observation of the cosmic microwave background (CMB). Moreover, the DM annihilation cross section required by the CR $e^\pm$ excess is also too large to generate the correct DM relic density with thermal production. In this work we use the Breit-Wigner mechanism with a velocity dependent DM annihilation cross section to reconcile these tensions. If DM particles accounting for the CR $e^\pm$ excess with $v\sim \mathcal{O}(10^{-3})$ are very close to a resonance in the physical pole case, their annihilation cross section in the Galaxy reaches a maximal value. On the other hand, the annihilation cross section would be suppressed for DM particles with smaller relative velocities in dwarf galaxies and at recombination, which may affect the gamma-ray and CMB observations, respectively. We find a proper parameter region that can simultaneously explain the AMS-02 results and the thermal relic density, while satisfying the Fermi-LAT and Planck constraints.

astro-ph.HE↗

arXiv2017

Measuring Masses in Semi-Invisible Final States at Electron-Positron Colliders

Mass measurement of a particle whose decay products including invisible particles is a challenging task at colliders. For a new physics model involving a dark matter candidate $N$ and a $Z_2$ symmetry that stabilizes it, a typical new process at $e^+e^-$ colliders is the pair production $e^+e^- \to Y\bar{Y}$ followed by decay processes $Y\to aN$ and $\bar{Y}\to b\bar{N}$, where $a$ and $b$ are visible but $N$ is invisible. In this work, we propose a new method to measure the physical masses in this topology by making use of the kinematic equations given by momentum-energy conservation and on-shell conditions. For each event, the solvability of these equations determines a limited region on the trial $m_Y$-$m_N$ plane. The edge of this region can be used to define two variables, $m_Y^\mathrm{edge}$ and $m_N^\mathrm{edge}$, whose distributions are utilized to derive the measurement values of $m_Y$ and $m_N$. The measurement deviations and uncertainties are also estimated after including detector effects and background contamination.

hep-ph↗

arXiv2016

Searching for Singlino-Higgsino Dark Matter in the NMSSM

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 $\tildeχ_1^0$ 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 $30 (300) \mathrm{fb}^{-1}$, $3l + E_\mathrm{T} \!\!\!\!\!\!\!/ \;\;\;$and $2l + E_\mathrm{T} \!\!\!\!\!\!\!/ \;\;\;$ searches at the 13 (14) TeV LHC are expected to reach up to $m_{\tildeχ_1^0}\sim 150 (230) \mathrm{GeV}$ and $m_{\tildeχ_2^0,\tildeχ_1^{\pm}}\sim 320 (480) \mathrm{GeV}$. Near future dark matter direct and indirect detection experiments can cover some parameter regions where collider searches lose their sensitivities.

hep-ph↗

arXiv2016

Equation of state and hybrid star properties with the weakly interacting light U-boson in relativistic models

It has been a puzzle whether quarks may exist in the interior of massive neutron stars, since the hadron-quark phase transition softens the equation of state (EOS) and reduce the neutron star (NS) maximum mass very significantly. In this work, we consider the light U-boson that increases the NS maximum mass appreciably through its weak coupling to fermions. The inclusion of the U-boson may thus allow the existence of the quark degrees of freedom in the interior of large mass neutron stars. Unlike the consequence of the U-boson in hadronic matter, the stiffening role of the U-boson in the hybrid EOS is not sensitive to the choice of the hadron phase models. In addition, we have also investigated the effect of the effective QCD correction on the hybrid EOS. This correction may reduce the coupling strength of the U-boson that is needed to satisfy NS maximum mass constraint. While the inclusion of the U-boson also increases the NS radius significantly, we find that appropriate in-medium effects of the U-boson may reduce the NS radii significantly, satisfying both the NS radius and mass constraints well.

nucl-th↗

arXiv2016

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

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.

hep-ph↗

arXiv2015

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

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.

hep-ph↗

arXiv2014

Relativistic symmetry breaking in light kaonic nuclei

As the experimental data from kaonic atoms and $K^{-}N$ scatterings imply that the $K^{-}$-nucleon interaction is strongly attractive at saturation density, there is a possibility to form $K^{-}$-nuclear bound states or kaonic nuclei. In this work, we investigate the ground-state properties of the light kaonic nuclei with the relativistic mean field theory. It is found that the strong attraction between $K^{-}$ and nucleons reshapes the scalar and vector meson fields, leading to the remarkable enhancement of the nuclear density in the interior of light kaonic nuclei and the manifest shift of the single-nucleon energy spectra and magic numbers therein. As a consequence, the pseudospin symmetry is shown to be violated together with enlarged spin-orbit splittings in these kaonic nuclei.

nucl-th↗

arXiv2014

Effects of fermionic dark matter on properties of neutron stars

By assuming that only gravitation exists between dark matter (DM) and normal matter (NM), we study the effects of fermionic DM on the properties of neutron stars using the two-fluid Tolman-Oppenheimer-Volkoff formalism. It is found that the mass-radius relationship of the DM admixed neutron stars (DANSs) depends sensitively on the mass of DM candidates, the amount of DM, and interactions among DM candidates. The existence of DM in DANSs results in a spread of mass-radius relationships that cannot be interpreted with a unique equilibrium sequence. In some cases, the DM distribution can surpass the NM distribution to form DM halo. In particular, it is favorable to form an explicit DM halo, provided the repulsion of DM exists. It is interesting to find that the difference in particle number density distributions in DANSs and consequently in star radii caused by various density dependencies of nuclear symmetry energy tends to disappear as long as the repulsion of accumulated DM is sufficient. These phenomena indicate that the admixture of DM in neutron stars can significantly affect the astrophysical extraction of nuclear equation of state by virtue of neutron star measurements. In addition, the effect of the DM admixture on the star maximum mass is also investigated.

astro-ph.SR↗