arXiv subjects

Yu-Feng Zhou

Publications and source records attributed to Yu-Feng Zhou.

At least 37 records · Page 2Linked to original sources

arXiv2022

Inherent color symmetry of quantum Yang-Mills theory

We present the basic non-perturbative structure of the space of classical dynamical solutions and corresponding one particle quantum states in SU(3) Yang-Mills theory. It has been demonstrated that the Weyl group of su(3) algebra plays an important role in constructing non-perturbative solutions and leads to profound changes in the structure of the classical and quantum Yang-Mills theory. We show that the Weyl group as a non-trivial color subgroup of SU(3) admits singlet irreducible representations on a space of classical dynamical solutions which lead to strict concepts of one particle quantum states for gluons and quarks. The Yang-Mills theory is a non-linear theory and, in general, it is not possible to construct a Hilbert space of classical solutions and quantum states as a linear vector space, so, usually, a perturbative approach is applied. We propose a non-perturbative approach based on Weyl symmetric solutions to full non-linear equations of motion and construct a full space of dynamical solutions representing an infinite but countable solution space classified by a finite set of integer numbers. It has been proved that the Weyl singlet structure of classical solutions provides the existence of a stable non-degenerate vacuum which serves as a main precondition of the color confinement phenomenon. Some physical implications in quantum chromodynamics are considered.

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arXiv2022

Constraining Time Dependent Dark Matter Signals from the Sun

Dark matter (DM) particles captured by the Sun can produce high energy electrons outside the Sun through annihilating into meta-stable mediators. The corresponding cosmic-ray electron signals observed by the space-based experiments will be time dependent due to the orbital motion of the space-based detectors. The shape of this time dependence is predictable given the orbital information of the detectors. Since the high-energy CR electron (with energy E>100 GeV) fluxes are expected to be constant in time, non-observation of such time variation can be used to place upper limits on the DM annihilation cross section. We analyze the time dependence of dark matter cosmic-ray signals in three space-based experiments: AMS-02, DAMPE and CALET. Under the assumption that no time dependent signal is observed, we derive the 95% C.L. exclusion limits on the signal strength from the current data. We map our limits onto the parameter space of the dark photon model and find that the constraints are comparable with that derived from the supernova SN1987A.

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arXiv2022

Production and attenuation of cosmic-ray boosted dark matter

Light sub-GeV halo dark matter (DM) particles up-scattered by high-energy cosmic-rays (CRs) (referred to as CRDM) can be energetic and become detectable by conventional DM direct detection experiments. We perform a refined analysis on the exclusion bounds of the spin-independent DM-nucleon scattering cross section $σ_{χp}$ in this approach. For the exclusion lower bounds, we determine the parameter of the effective distance $D_\text{eff}$ for CRDM production using spatial-dependent CR fluxes and including the contributions from the major heavy CR nuclear species. We obtain $D_\text{eff}\simeq 9$ kpc for CRDM particles with kinetic energy above $\sim 1~\text{GeV}$, which pushes the corresponding exclusion lower bounds down to $σ_{χp} \sim 4\times 10^{-32}~\text{cm}^2$ for DM particle mass at MeV scale and below. For the exclusion upper bounds from Earth attenuation, previous estimations neglecting the nuclear form factor leaded to typical exclusion upper bounds of $σ_{χp}\sim\mathcal{O}(10^{-28})~\text{cm}^2$ from the XENON1T data. Using both the analytic and numerical approaches, we show that for CRDM particles, the presence of the nuclear form factor strongly suppresses the effect of Earth attenuation. Consequently, the cross section that can be excluded by the XENON1T data can be a few orders of magnitude higher, which closes the gap in the cross sections excluded by the XENON1T experiment and that by the astrophysical measurements such that for the cosmic microwave background (CMB), galactic gas cloud cooling, and structure formation, etc..

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arXiv2021

Pseudo-Dirac Sterile Neutrino Dark Matter

Sterile neutrino is a promising dark matter (DM) candidate. However the parameter space of this scenario has almost been ruled out by the X-ray observation results whenever the sterile neutrino is solely produced by the Dodelson-Widrow (DW) mechanism in the early Universe. In this letter we propose an extension to the minimal sterile neutrino DM model by introducing the pseudo-Dirac sterile neutrino, which implies the existence of two nearly degenerate Majorana states $\hat N_{1,2}^{}$, and a permutation symmetry. The heavy state $\hat N_1$ is produced via the DW mechanism, and the light state $\hat N_2$, which serves as the DM, is produced from the decay of $\hat N_1$ in the early Universe. The X-ray constraint is avoided by the permutation symmetry, which forbidden the two-body decay of the DM into active neutrinos and photon. A promising signal of this scenario is the effective number of neutrino species, which will be precisely measured in future experiments, such as CMB stage IV. We further study the impact of this model on the cosmological parameters. The Markov Chain Monte Carlo analysis for the Planck + BAO+R19 data gives $H_0=69.2_{-0.59}^{+0.58}$, which may relieve the Hubble tension.

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arXiv2021

Consistent explanation for the cosmic-ray positron excess in $p$-wave Breit-Wigner enhanced dark matter annihilation

Dark matter (DM) annihilation in the galactic halo can be enhanced relative to that in the early Universe due to the Breit-Wigner enhancement, if the DM particles annihilate through a narrow resonance. Although the $s$-wave Breit-Wigner enhancement can provide a consistent explanation for both the observed cosmic-ray (CR) positron excess and the DM thermal relic density, it is severely constrained by the observations of gamma rays from dwarf spheroidal satellite galaxies (dSphs) and the cosmic microwave background (CMB), which have relatively lower allowed DM annihilation cross section and typical DM velocities than that in the galactic halo. Furthermore, in the $s$-wave Breit-Wigner enhancement, the case where the resonance mass is below a threshold (twice the DM mass) is ruled out due to the monotonically increasing annihilation cross section with decreasing DM velocity. In this work, we consider Breit-Wigner enhanced $p$-wave DM annihilation. We explore the parameter regions which can simultaneously account for the CR positron excess and DM thermal relic density without violating the constraints from dSphs gamma rays and CMB. We show that the velocity-dependent cross section in this scenario can peak around the typical DM velocity in the galactic halo for the resonance mass both above and below the threshold. Moreover, the highly suppressed annihilation cross section at extremely low DM velocity can evade the constraints from dSphs gamma rays and CMB easily, which results in larger allowed parameter regions than that in the $s$-wave case.

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arXiv2021

Consistent explanation for the cosmic-ray positron excess in p-wave Sommerfeld-enhanced dark matter annihilation

Sommerfeld-enhanced dark matter (DM) annihilation through $s$-wave has been widely considered as a consistent explanation for both the observed cosmic-ray (CR) positron excess and the DM thermal relic density. However, as the $s$-wave Sommerfeld-enhanced annihilation cross section increases monotonically with decreasing DM velocity, severe constraints appear from the data of gamma rays from dwarf spheroidal satellite galaxies (dSphs) and the cosmic microwave background (CMB), as the relevant typical DM velocities are even lower than that in the Galactic halo. In this work, we consider Sommerfeld-enhanced $p$-wave DM annihilation where the DM annihilation cross section can be enhanced at certain velocities but eventually be highly suppressed when the DM velocities become extremely low. We calculate the velocity-dependent astrophysics factors ($J$-factors) for the Sommerfeld-enhanced $p$-wave DM annihilation for fifteen nearby dSphs. Taking the channel of DM annihilating into $4μ$ through two light mediators as an example, we show that there are parameter regions where this mechanism can account for the CR positron excess and the DM relic density, while being compatible with the constraints from dSphs gamma rays measured by Fermi-LAT and that from the CMB measured by PLANCK.

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arXiv2021

Constraining light dark matter upscattered by ultrahigh-energy cosmic rays

Light halo dark matter (DM) particles upscattered by high-energy cosmic rays (CRs) can be energetic, and become detectable by conventional direct detection experiments. The current constraints derived from space-based direct CR measurements can reach $\mathcal{O}(10^{-31})\text{ cm}^{2}$ for a constant DM-nucleon scattering cross section. We show that if the CR energy spectrum follows a power law of type $\sim E^{-3}$, the derived constraints on the scattering cross section will be highly insensitive to DM particle mass. This suggests that ultrahigh-energy CRs (UHECRs) indirectly measured by ground-based detectors can be used to place constraints on ultralight DM particles, as $E^{-3}$ is a very good approximation of the UHECR energy spectrum up to energy $\sim10^{20}\text{ eV}$. Using the recent UHECR flux data, we show that the current constraints derived from space-based CR measurements can in principle be extended to ultralight DM particles far below eV scale.

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arXiv2021

Implications of a possible TeV break in the cosmic-ray electron and positron flux

A TeV spectral break in the total flux of cosmic-ray electrons and positrons (CREs) at which the spectral power index softens from $\sim 3$ to $\sim 4$ has been observed by H.E.S.S. and recently confirmed by DAMPE with a high significance of $6.6~σ$. Such an observation is apparently inconsistent with the data from other experiments such as Fermi-LAT, AMS-02 and CALET. We perform a global analysis to the latest CRE data including Fermi-LAT, AMS-02, CALET, DAMPE and H.E.S.S. with energy scale uncertainties taken into account to improve the consistency between the data sets. The fit result strongly favors the existence of the break at $\sim 1$ TeV with an even higher statistical significance of $13.3~σ$. In view of the tentative CRE break, we revisit a number of models of nearby sources, such as a single generic Pulsar Wind Nebula (PWN), known multiple PWNe from the ATNF catalog, and their combinations with either an additional Dark Matter (DM) component or a Supernova Remnant (SNR). We show that the CRE break at $\sim 1$ TeV, together with the known CR positron excess points towards the possibility that the nearby sources should be highly charge asymmetric. Among the models under consideration, the one with a PWN plus SNR is most favored by the current data. The favoured distance and age of the PWN and SNR sources are both within $0.6$ kpc and around $10^{5}$ yr respectively. Possible candidate sources include PSR J0954-5430, Vela and Monogem ring, etc. We find that for the models under consideration, the additional DM component is either unnecessary, or predicts too much photons in tension with the H.E.S.S. data of $γ$-rays from the direction of the Galactic Center. We also show that the current measurement of the anisotropies in the arrival direction of the CRE can be useful in determining the property of the sources.

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arXiv2021

Axion-like particle inflation and dark matter

In this paper, we propose a generalized natural inflation (GNI) model to study axion-like particle (ALP) inflation and dark matter (DM). GNI contains two additional parameters $(n_1, n_2)$ in comparison with the natural inflation, that make GNI more general. The $n_1$ build the connection between GNI and other ALP inflation model, $n_2$ controls the inflaton mass. After considering the cosmic microwave background and other cosmological observation limits, the model can realize small-field inflation with a wide mass range, and the ALP inflaton considering here can serve as the DM candidate for certain parameter spaces.

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arXiv2021

The high energy window of probing dark matter with cosmic-ray antideuterium and antihelium

Cosmic-ray (CR) anti-nuclei are often considered as important observables for dark matter (DM) indirect detections at low kinetic energies below GeV per nucleon. Since the primary CR fluxes drop quickly towards high energies, the secondary anti-nuclei in CR are expected to be significantly suppressed in high energy regions ($\gtrsim 100$ GeV per nucleon). If DM particles are heavy, the annihilation productions of DM can be highly boosted, thus the fluxes of anti-nuclei produced by DM annihilations may exceed the secondary background at high energies, which opens a high energy window for DM indirect detections. We investigate the possibility of detecting heavy DM particles which annihilate into high energy anti-nuclei. We use Monte-Carlo generators $\texttt{PYTHIA}$, $\texttt{EPOS-LHC}$ and $\texttt{DPMJET}$ and the coalescence model to simulate the production of anti-nuclei, and constrain the DM annihilation cross sections by using the AMS-02 and HAWC antiproton data and the HESS galactic center gamma-ray data. We find that the conclusion depends on the choice of DM density profiles. For the "Cored" type profile with a DM particle mass $\gtrsim 10$ TeV, the contributions from DM annihilations can exceed the secondary background in high energy regions, which opens the high energy window. While for the "Cuspy" type profile, the excess disappears.

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arXiv2021

Constraints on a mixed model of dark matter particles and primordial black holes from the Galactic 511 keV line

The galactic 511 keV gamma-ray line has been observed since 1970's, and was identified as the result of electron-positron annihilation, but the origin of such positrons is still not clear. Apart from the astrophysical explanations, the possibilities that such positrons come from dark matter (DM) annihilation are also widely studied. Primordial black hole (PBH) is also an extensively studied candidate of DM. If PBHs exist, the DM particles may be gravitationally bound to the PBHs and form halo around PBHs with density spikes. DM annihilation in these density spikes can enhance the production rate of positrons from DM particles, but the signal morphology is similar to the decaying DM. We consider such a mixed model consisting of DM particles and PBHs and obtain the upper limit from the data of 511 keV gamma-ray line from INTEGRAL/SPI on the decaying component of DM particles and the constraint on the PBH abundance. These constraints are general and independent of particle DM models. For the mixed model consisting of excited DM and PBHs, the constraints on the PBH abundance can be down to $O(10^{-17})$ for DM particle with mass around $1~\mathrm{TeV}$, which is more stringent than that obtained from the extragalactic gamma-ray background.

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arXiv2020

Color confinement and color singlet structure of quantum states in Yang-Mills theory

We consider two fundamental long-standing problems in quantum chromodynamics (QCD): the origin of color confinement and structure of a true vacuum and color singlet quantum states. There is a common belief that resolution to these problems needs a knowledge of a strict non-perturbative quantum Yang-Mills theory and new ideas. Our principal idea in resolving these problems is that structure of color confinement and color singlet quantum states must be determined by a Weyl symmetry which is an intrinsic symmetry of the Yang-Mills gauge theory, and by properties of a selected class of solutions satisfying special requirements. Following this idea we construct for the first time a space of color singlet one particle quantum states for primary gluons and quarks and reveal the structure of color confinement in quantum Yang-Mills theory. As an application we demonstrate formation of physical observables in a pure QCD, pure glueballs.

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arXiv2019

Constraints on dark matter interactions from the first results of DarkSide-50

In an extended effective operator framework of isospin violating interactions with light mediators, we investigate the compatibility of the candidate signal of the CDMS-II-Si with the latest constraints from DarkSide-50 and XENON-1T, etc. We show that the constraints from DarkSide-50 which utilizes Argon as the target is complementary to that from XENON-1T which utilizes Xenon. Combining the results of the two experiments, we find that for isospin violating interaction with light mediator there is no parameter space which can be compatible with the positive signals from CDMS-II-Si. As a concrete example of this framework, we investigate the dark photon model in detail. We obtain the combined limits on the dark matter mass $m_χ$, the dark photon mass $m_{A'}$, and the kinetic mixing parameter $\varepsilon$ in the dark photon model. The DarkSide-50 gives more stringent upper limits in the region of mediator mass from 0.001 to 1 GeV, for $m_χ \lesssim 6$ GeV in the ($m_{A'}$,$\varepsilon$) plane, and more stringent constraints for $m_χ\lesssim 8$ GeV and $\varepsilon \thicksim 10^{-8}$ in the ($m_χ$,$m_{A'}$) plane.

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arXiv2019

Prospects of detecting dark matter through cosmic-ray antihelium with the antiproton constraints

Cosmic-ray (CR) antihelium is an important observable for dark matter (DM) indirect searches due to extremely low secondary backgrounds towards low energies. In a given DM model, the predicted CR antihelium flux is expected to be strongly correlated with that of CR antiprotons. In this work, we use the AMS-02 $\bar p/p$ data to constrain the DM annihilation cross section, and the ALICE data on the $^3\overline{\text{He}}$ and $\overline{\text{T}}$ productions to determine the parameters in the coalescence model for anti-nucleus formation. The hadronic cross sections are estimated using Monte-Carlo event generators including $\texttt{EPOS-LHC}$ and $\texttt{DPMJET}$. Based on these constraints, we make predictions for the maximal antihelium flux for typical DM annihilation final states, and perform a detailed analysis on the uncertainties due to the DM density profiles and CR propagation models. We find that the results are highly insensitive to both of them, but still significantly depends on the hadronization models in event generators. The prospects of detecting antihelium for the AMS-02 experiment is discussed. We show that with very optimistic assumptions, CR $^3\overline{\text{He}}$ is within the reach of the AMS-02 experiment. The $^3\overline{\text{He}}$ events which can be detected by AMS-02 are likely to have kinetic energy $T \gtrsim 30$~GeV, which is consistent with the preliminary AMS-02 search results. The events which can be observed by AMS-02 are likely to arise dominantly from secondary backgrounds rather than DM interactions.

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arXiv2018

Astrophysical background and dark matter implication based on latest AMS-02 data

The cosmic ray(CR) positrons and antiprotons are often regarded as the collision products of CR nucleons with the interstellar medium. However this conclusion is challenged by recent experimental data. In this work, we choose the latest AMS-02 data to analyze the astrophysical background of CR positrons and antiprotons with the GALPROP code for CR propagation and the QGSJET-II-04 model for the hadronic interactions. The results show that in low energies the predicted fluxes of CR antiprotons and positrons are consistent with AMS-02 data in the diffusion model combining the re-acceleration and convection terms (DCR model). Thus, the excess of CR antiprotons in the low energy are not justified. In that model, the predicted flux of CR protons is consistent with AMS-02 data whose hardening feature above 330 GeV is also matched. Based on that model, the total fluxes of CR electrons and positrons from AMS-02 are also used to analyzed the interpretation of dark matter annihilation about the positron excess. The predicted best-fit masses of dark matter are from 400 GeV to 4 TeV. The DCR model does not give the unusual interpretation of the positron excess.

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arXiv2018

Damping of gravitational waves in a viscous Universe and its implication for dark matter self-interactions

It is well known that a gravitational wave (GW) experiences the damping effect when it propagates in a fluid with nonzero shear viscosity. In this paper, we propose a new method to constrain the GW damping rate and thus the fluid shear viscosity. By defining the effective distance which incorporates damping effects, we can transform the GW strain expression in a viscous Universe into the same form as that in a perfect fluid. Therefore, the constraints of the luminosity distances from the observed GW events by LIGO and Virgo can be directly applied to the effective distances in our formalism. We exploit the lognormal likelihoods for the available GW effective distances and a Gaussian likelihood for the luminosity distance inferred from the electromagnetic radiation observation of the binary neutron star merger event GW170817. Our fittings show no obvious damping effects in the current GW data, and the upper limit on the damping rate with the combined data is $6.75 \times 10^{-4}\,{\rm Mpc}^{-1}$ at 95\% confidence level. By assuming that the dark matter self-scatterings are efficient enough for the hydrodynamic description to be valid, we find that a GW event from its source at a luminosity distance $D\gtrsim 10^4\;\rm Mpc$ can be used to put a constraint on the dark matter self-interactions.

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arXiv2018

Constraints on the Sommerfeld-enhanced dark matter annihilation from the gamma rays of subhalos and dwarf galaxies

The substructures of the Galactic dark matter halo such as dark matter subhalos and dwarf galaxies have very low velocity dispersions, which makes them useful in constraining the scenario of Sommerfeld-enhanced dark matter annihilation. We calculate the velocity distribution of dark matter particles in dark matter halo substructures using the Eddington's formula with NFW density profile. We parametrize the effect of Sommerfeld enhancement of s-wave dark matter annihilation on the gamma-ray flux as the Sommerfeld-enhanced J-factors, and explicitly calculate their values for 15 known dwarf spheroidal galaxies. Using the Fermi-LAT 3FGL data on the unassociated point-sources and the N-body simulation results on the dark matter subhalo distribution, we derive upper limits on the dark matter annihilation cross sections with Sommerfeld enhacement. Similar upper limits are derived from the Ferm-LAT gamma-ray data on the dwarf spheroidal galaxies. We find that in a wide region of parameter space, the constraints can be a few orders of magnitude more stringent than that in the case without the Sommerfeld enhancement. For dark matter annihilation dominantly into $e^+e^-$, $μ^+μ^-$, $τ^{+}τ^{-}$ and $b\bar b$, those constraints can exclude thermal relic dark matter for the dark matter mass below about 1 TeV.

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arXiv2018

Origins of sharp cosmic-ray electron structures and the DAMPE excess

Nearby sources may contribute to cosmic-ray electron (CRE) structures at high energies. Recently, the first DAMPE results on the CRE flux hinted at a narrow excess at energy ~1.4 TeV. We show that in general a spectral structure with a narrow width appears in two scenarios: I) "Spectrum broadening" for the continuous sources with a delta-function-like injection spectrum. In this scenario, a finite width can develop after propagation through the Galaxy, which can reveal the distance of the source. Well-motivated sources include mini-spikes and subhalos formed by dark matter (DM) particles $χ_{s}$ which annihilate directly into e+e- pairs. II) "Phase-space shrinking" for burst-like sources with a power-law-like injection spectrum. The spectrum after propagation can shrink at a cooling-related cutoff energy and form a sharp spectral peak. The peak can be more prominent due to the energy-dependent diffusion. In this scenario, the width of the excess constrains both the power index and the distance of the source. Possible such sources are pulsar wind nebulae (PWNe) and supernova remnants (SNRs). We analysis the DAMPE excess and find that the continuous DM sources should be fairly close within ~0.3 kpc, and the annihilation cross sections are close to the thermal value. For the burst-like source, the narrow width of the excess suggests that the injection spectrum must be hard with power index significantly less than two, the distance is within ~(3-4) kpc, and the age of the source is ~0.16 Myr. In both scenarios, large anisotropies in the CRE flux are predicted. We identify possible candidates of mini-spike (PWN) sources in the current Fermi-LAT 3FGL (ATNF) catalog. The diffuse gamma-rays from these sources can be well below the Galactic diffuse gamma-ray backgrounds and less constrained by the Ferm-LAT data, if they are located at the low Galactic latitude regions.

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