arXiv subjects

Yupeng Yang

Publications and source records attributed to Yupeng Yang.

47 records · Page 3Linked to original sources

arXiv2018

Contributions of dark matter annihilation to the global 21cm spectrum observed by the EDGES experiment

The EDGES experiment has observed an absorption feature in the global 21 cm spectrum with a surprisingly large amplitude. These results can be explained by decreasing the kinetic temperature of baryons, which could be achieved through the scattering between the baryons and cold dark matter particles. It seems that the most researched dark matter annihilation model is not able to explain such a large amplitude, since the interactions between the particles produced by the dark matter annihilation and the particles that have been present in the Universe could increase the baryonic temperature. Recently, C. Feng and G. Holder have suggested that the large amplitude in the global 21 cm spectrum could be produced by considering the possible excess of the early radio radiation. In this paper, we propose that the dark matter annihilation still works to explain the large amplitude observed by the EDGES experiment. Even including the dark matter annihilation, the large absorption amplitude in the global 21 cm spectrum can be produced by considering the possible excess of the early radio radiation.

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arXiv2017

Tau neutrinos from ultracompact dark matter minihalos and constraints on the primordial curvature perturbations

The observations and research on the neutrinos provide a kind of indirect way of revealing the properties of dark matter particles. For the detection of muon neutrinos, the main issue is the large atmospheric background, which is caused by the interactions between the cosmic rays and atoms within the atmosphere. Compared with muon neutrinos, tau neutrinos have a smaller atmospheric background especially for the downward-going direction. Except for the classical neutrino sources, dark matter particles can also annihilate into the neutrinos and are the potential high energy astrophysical sources. The annihilation rate of dark matter particles is proportional to the square of number density; therefore, the annihilation rate is large near the center of dark matter halos especially for the new kind of dark matter structures named ultracompact dark matter minihalos (UCMHs). In previous works, we have investigated the potential muon neutrino flux from UCMHs due to dark matter annihilation. Moreover, since the formation of UCMHs is related to the primordial density perturbations of small scales, we get the constraints on the amplitude of the primordial curvature perturbations of small scales, $1 \lesssim k \lesssim 10^{7} ~\rm Mpc^{-1}$. In this work, we focus on the downward-going tau neutrinos from UCMHs due to dark matter annihilation. Compared with the background of tau neutrino flux we get the constraints on the mass fraction of UCMHs. Then using the limits on the mass fraction of UCMHs we got the constraints on the amplitude of the primordial curvature perturbations which are extended to the scale $k \sim 10^{8} ~ \rm Mpc^{-1}$ compared with previous results.

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arXiv2016

Contributions of dark matter annihilation within ultracompact minihalos to the 21cm background signal

In the dark age of the universe, any exotic sources, e.g. the dark matter annihilation, which inject the energy into the intergalactic medium (IGM) will left some imprint on the 21cm background signal. Recently, one new kind of dark matter structure named ultracompact dark matter minihalo (UCMHs) was proposed. Near the inner part UCMHs, the distribution of dark matter particles are steeper than that of the general dark matter halos, $ρ_{\rm UCMHs}(r) \sim r^{-2.25}$, and the formation time of UCMHs is earlier, $z_c \sim 1000$. Therefore, it is excepted that the dark matter annihilation within UCMHs can effect the 21cm background signal. In this paper, we investigated the contributions of the dark matter annihilation within UCMHs to the 21cm background signal.

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arXiv2015

Constraints on the basic parameters of dark matter using the Planck data

Dark Matter annihilation or decay can affect the anisotropy of the cosmic microwave background (CMB). Therefore, the CMB data can be used to constrain the properties of a dark matter particle. In this work, we use the new CMB data obtained by the Planck satellite to investigate the limits on the basic parameters of a dark matter particle. The parameters are the dark matter mass ($m_χ$) and the thermally averaged cross section ($\langleσv\rangle$) for dark matter annihilation and the decay rate ($Γ$) (or lifetime $τ= 1/Γ$) for dark matter decay. For dark matter annihilation we also consider the impact of the structure formation process which is neglected by the recent work. We find that for DM annihilation, the constraints on the parameters are $f_{ann}=\langle σv\rangle /m_χ< 0.16 \times 10^{-26} \mathrm{cm^{3}s^{-1}GeV^{-1}}$(or $f_{ann}<0.89 \times 10^{-6} \mathrm{m^{3}s^{-1}kg^{-1}}$, $95\%$ C.L.). For DM decay, the constraints on the decay rate are $Γ< 0.28 \times 10^{-25} \mathrm{s^{-1}}$($95\%$ C.L.).

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arXiv2015

Constraints on the primordial power spectrum of small scales using the neutrino signals from the dark matter decay

Many inflation theories predict that the primordial power spectrum is scale invariant. The amplitude of the power spectrum can be constrained by different observations such as the cosmic microwave background (CMB), Lyman-$α$, large-scale structures and primordial black holes (PBHs). Although the constraints from the CMB are robust, the corresponding scales are very large ($10^{-4} 1 \mathrm{Mpc^{-1}}$), the research on the PBHs provides much weaker limits. Recently, ultracompact dark matter minihalos (UCMHs) was proposed and it was found that they could be used to constraint the small-scale primordial power spectrum. The limits obtained by the research on the UCMHs are much better than that of PBHs. Most of previous works focus on the dark matter annihilation within the UCMHs, but if the dark matter particles do not annihilate the decay is another important issue. In previous work~\cite{EPL}, we investigated the gamma-ray flux from the UCMHs due to the dark matter decay. In addition to these flux, the neutrinos are usually produced going with the gamma-ray photons especially for the lepton channels. In this work, we studied the neutrino flux from the UCMHs due to the dark matter decay. Finally, we got the constraints on the amplitude of primordial power spectrum of small scales.

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arXiv2013

Neutrino signals from ultracompact minihalos and constraints on the primordial curvature perturbation

Compared with that of standard dark matter halos, the density profile of the recently proposed new kind of dark matter structure named ultracompact minihalos (UCMHs) is steeper and its formation time is earlier. If the dark matter is composed of weakly interactive massive particles (WIMP), the potential signals, e.g. neutrinos, from UCMHs due to the dark matter annihilation would be detected by IceCube/DeepCore or other detectors and such signals would have a very useful complementarity of gamma rays observations. On the other hand, the formation of UCMHs is related to primordial curvature perturbations on the smaller scales. So constraints on the abundance of UCMHs can be used to give a limit on the perturbations on these scales. In previous works in the literature, the authors focused on the γ-ray signals from UCMHs due to dark matter annihilation. In this work, we investigate the neutrino signals from nearby UCMHs. Although no excess of neutrino signals the dark matter annihilation has been observed, the constraints on the abundance of UCMHs can be obtained and these constraints can be translated into the limit on the primordial curvature perturbations on small scales.

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arXiv2013

The contribution of ultracompact dark matter minihalos to the isotropic radio background

The ultracompact minihalos could be formed during the earlier epoch of the universe. The dark matter annihilation within them is very strong due to the steep density profile, $ρ\sim r^{-2.25}$. The high energy electrons and positrons from the dark matter annihilation can inverse Compton scatter (ICS) with the background photons, such as CMB photons, to acquire higher energy. On the other hand, the synchrotron radiation can also be produced when they meet the magnetic field. In this paper, we study the signals from the UCMHs due to the dark matter annihilation for the radio, X-ray and $γ$-ray band. We found that for the radio emission the UCMHs can provide one kind of source for the radio excess observed by ARCADE 2. But the X-ray signals due to the ICS effect or the $γ$-ray signals mainly due to the prompt emission from dark matter would exceed the present observations, such as Fermi, COMPTEL and CHANDRA. We found that the strongest limits on the fraction of UCMHs come from the X-ray observations and the constraints from the radio data are the weakest.

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arXiv2013

Dark Matter Decay and the Abundance of Ultracompact Minihalos

Ultracompact minihalos would be formed if there are larger density perturbations ($0.0003 < δρ/ρ< 0.3$) in the earlier epoch. The density profile of them is steeper than the standard dark matter halos. If the dark matter can annihilate or decay into the standard particles, e.g., photons, these objects would be the potential astrophysical sources. In order to be consistent with the observations, such as $Fermi$, the abundance of ultracompact minihalos must be constrained. On the other hand, the formation of these objects has very tight relation with the primordial curvature perturbations on smaller scale, so the fraction of ultracompact minihalos is very important for modern cosmology. In previous works, the studies are focused on the dark matter annihilation for these objects. But if the dark matter is not annihilated, the dark matter decay is another important possible case. On the other hand, the abundance of ultracompact minihalos is related to many other parameters, such as the mass of dark matter, the decay channels and the density profile of dark matter halo. One of the important aspects of this work is that we investigate the $γ$-ray signals from nearby ultracompact minihalos due to dark matter decay and another important aspect is to study in detail how the different decay channels and density profiles affect the constraints on the abundance of ultracompact minihalos.

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arXiv2011

Constraints on ultracompact minihalos from extragalactic γ-ray background

It has been proposed that ultracompact minihalos (UCMHs) might be formed in earlier epoch. If dark matter consists of Weakly Interacting Massive Particles (WIMPs), UCMHs can be treated as the γ-ray sources due to dark matter annihilation within them. In this paper, we investigate the contributions of UCMHs formed during three phase transi- tions (i.e., electroweak symmetry breaking, QCD confinement and e+ e- annihilation) to the extragalactic γ-ray background. Moreover, we use the Fermi-LAT observation data of the extragalactic γ-ray background to get the constraints on the current abundance of UCMHs produced during these phase transitions. We also compare these results with those obtained from Cosmic Microwave Background (CMB) observations and find that the constraints from the Fermi-LAT are more stringent than those from CMB

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arXiv2011

The Abundance of New Kind of Dark Matter Structures

A new kind of dark matter structures, ultracompact minihalos (UCMHs) was proposed recently. They would be formed during the radiation dominated epoch if the large density perturbations are existent. Moreover, if the dark matter is made up of weakly interacting massive particles, the UCMHs can have effect on cosmological evolution because of the high density and dark matter annihilation within them. In this paper, one new parameter is introduced to consider the contributions of UCMHs due to the dark matter annihilation to the evolution of cosmology, and we use the current and future CMB observations to obtain the constraint on the new parameter and then the abundance of UCMHs. The final results are applicable for a wider range of dark matter parameters

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arXiv2011

New Constraints on Primordial Minihalo Abundance Using Cosmic Microwave Background Observations

It was proposed that the massive compact halo objects (MCHOs) would be produced during an earlier epoch of cosmology if the density perturbations are between $3 \times 10^{-4}$ and 0.3. Then these objects can accrete dark matter particles onto them due to their high density. If the dark matter is in the form of the weakly interacting massive particles, the MCHOs can have a significant effect on the evolution of cosmology due to the dark matter annihilation within them. Using the WMAP-7 years data, we investigated the constraints on the current abundance of MCHOs ($f_{MCHOs}$) formed during the $e^{+} e^{-}$ annihilation phase transition. We have found that the $2σ$ constraint is $f_{MCHOs} \lesssim 10^{-4}$ for dark matter masses in the range between 1 GeV and 1 TeV.

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