arXiv subjects

Lei Zu

Publications and source records attributed to Lei Zu.

23 records · Page 2Linked to original sources

arXiv2020

Stringent constraints on the light boson model with supermassive black hole spin measurements

Massive bosons, such as light scalars and vector bosons, can lead to instabilities of rotating black holes by the superradiance effect, which extracts energy and angular momentum from rapidly-rotating black holes effectively. This process results in spinning-down of black holes and the formation of boson clouds around them. In this work, we used the masses and spins of supermassive black holes measured from the ultraviolet/optical or X-ray observations to constrain the model parameters of the light bosons. We find that the mass range of light bosons from $10^{-22}$ eV to $10^{-17}$ eV can be largely excluded by a set of supermassive black holes (including also the extremely massive ones OJ 287, Ton 618 and SDSS J140821.67+025733.2), particularly for the vector boson scenario, which eliminates a good fraction of the so-called fuzzy dark matter parameter regions. For the scalar bosons with self-interaction, most part of the mass range from $\sim 3 \times 10^{-19}$ eV to $10^{-17}$ eV with a decay constant $f_a > 10^{15}$ GeV can be excluded, which convincingly eliminate the QCD axions at these masses.

astro-ph.HE↗

arXiv2020

Plasma dark matter and electronic recoil events in XENON1T

Dark matter might be in the form of a dark plasma in the Milky Way halo. Specifically, we consider here a hidden sector consisting of a light `dark electron' and a much heavier `dark proton', each charged under an unbroken $U(1)'$ gauge symmetry. These self-interacting dark sector particles can also interact with ordinary matter via the kinetic mixing interaction, and lead to a signal in dark matter direct detection experiments. Indeed, keV electron recoils can arise quite naturally in such models from dark electron scattering off loosely bound atomic electrons. Here we examine the recently reported XENON1T excess in the context of such a plasma dark matter model. We find that the observed excess can be explained if kinetic mixing is in the approximate range: $10^{-12} \lesssim ε\lesssim 10^{-10}$. The allowed parameter space is consistent with astrophysical and cosmological constraints and consistent also with other direct detection experiments.

hep-ph↗

arXiv2018

Constraints on box-shaped cosmic ray electron feature from dark matter annihilation with the AMS-02 and DAMPE data

Precise measurements of spectra of cosmic ray electrons and positrons can effectively probe the nature of dark matter (DM) particles. In a class of models where DM particles initially annihilate into a pair of intermediate particles which then decay into standard model particles, box-shaped spectra can be generated. Such a kind of spectra are distinct from astrophysical backgrounds, and can probably be regarded as characteristic features of the DM annihilation. In this work, we search for such a feature in the total electron plus positron spectrum measured by AMS-02 and DAMPE. No significant evidence for such a DM annihilation component has been found. The 95\% confidence level upper limits of the velocity-weighted annihilation cross section are derived, which range from $\sim 10^{-26}~{\rm cm^3~s^{-1}}$ for DM mass of 50 GeV to $\sim 10^{-23}~{\rm cm^3~s^{-1}}$ for DM mass of 10 TeV.

hep-ph↗

arXiv2018

Explaining the DAMPE data with scalar dark matter and gauged $U(1)_{L_e-L_μ}$ interaction

Inspired by the peak structure observed by recent DAMPE experiment in $e^+e^-$ cosmic-ray spectrum, we consider a scalar dark matter (DM) model with gauged $U(1)_{L_e-L_μ}$ symmetry, which is the most economical anomaly-free theory to potentially explain the peak by DM annihilation in nearby subhalo. We utilize the process $χχ\to Z^\prime Z^\prime \to l \bar{l} l^\prime \bar{l}^\prime$, where $χ$, $Z^\prime$, $l^{(\prime)}$ denote the scalar DM, the new gauge boson and $l^{(\prime)} =e, μ$, respectively, to generate the $e^+e^-$ spectrum. By fitting the predicted spectrum to the experimental data, we obtain the favored DM mass range $m_χ\simeq 3060^{+80}_{-100} \, {\rm GeV}$ and $Δm \equiv m_χ- m_{Z^\prime} \lesssim 14 \, {\rm GeV}$ at $68\%$ Confidence Level (C.L.). Furthermore, we determine the parameter space of the model which can explain the peak and meanwhile satisfy the constraints from DM relic abundance, DM direct detection and the collider bounds. We conclude that the model we consider can account for the peak, although there exists a tension with the constraints from the LEP-II bound on $m_{Z^\prime}$ arising from the cross section measurement of $e^+e^- \to Z^{\prime\ast} \to e^+ e^-$.

hep-ph↗

arXiv2018

Scalar dark matter explanation of the DAMPE data in the minimal Left-Right symmetric model

Left-Right symmetric model (LRSM) has been an attractive extension of the Standard Model (SM) which can address the origin of parity violation in the SM electroweak (EW) interactions, generate tiny neutrino masses, accommodate dark matter (DM) candidates and provide a natural framework for baryogenesis through leptogenesis. In this work we utilize the minimal LRSM to study the recently reported DAMPE results of cosmic $e^+e^-$ spectrum which exhibits a tentative peak around 1.4 TeV, while satisfying the current neutrino data. We propose to explain the DAMPE peak with a complex scalar DM $χ$ in two scenarios: 1) $χχ^* \to H_1^{++}H_1^{--} \to \ell_i^+\ell_i^+\ell_j^-\ell_j^-$; 2) $χχ^* \to H_{k}^{++}H_{k}^{--} \to \ell_i^+\ell_i^+\ell_j^-\ell_j^-$ accompanied by $χχ^* \to H_1^+ H_1^- \to \ell_i^+ ν_{\ell_i} \ell_j^- ν_{\ell_j}$ with $\ell_{i,j}=e,μ,τ$ and $k=1,2$. We fit the theoretical prediction on $e^+e^-$ spectrum to relevant experimental data to determine the scalar mass spectrum favored by the DAMPE excess. We also consider various constraints from theoretical principles, collider experiments as well as DM relic density and direct search experiments. We find that there are ample parameter space which can interpret the DAMPE data while passing the constraints. Our explanations, on the other hand, usually imply the existence of other new physics at the energy scale ranging from $10^7 {\rm GeV}$ to $10^{11} {\rm GeV}$. Collider tests of our explanations are also discussed.

hep-ph↗