对于湮没导致电子-正电子对产生的情况，我们确定了暗物质（DM）自湮没截面的上限。在银河系中心（GC），相对论性电子和正电子通过同步辐射产生射电通量，并通过韧致辐射和逆康普顿散射产生伽马射线通量。根据档案、干涉测量和单碟射电数据，我们确定了银河系中心周围3度半长轴（沿银河系平面）和1度半短轴的椭圆区域的射电频谱，以及第二个矩形区域，也以GC为中心，范围为1.6度x0.6度。这两个地区的无线电频谱在我们有数据的频率范围内是非热的：74 MHz - 10 GHz。我们还考虑伽马射线数据覆盖同一地区的EGRET仪器（约GeV）和HESS（约TeV）。我们展示了如何将这些数据的组合，可以用来放置强大的DM湮灭的情况下，在某种程度上，这是相对不敏感的假设在该地区的磁场振幅的约束。我们的结果是大约一个数量级的限制比现有的银河系中心的无线电和伽马射线的限制。对于质量为m_x =10 GeV的DM和NFW分布，我们发现速度平均截面必须小于10^-25 cm ^3·s^-1的数倍。
英文摘要：
We determine upper limits on the dark matter (DM) self-annihilation cross section for scenarios in which annihilation leads to the production of electron--positron pairs. In the Galactic centre (GC), relativistic electrons and positrons produce a radio flux via synchroton emission, and a gamma ray flux via bremsstrahlung and inverse Compton scattering. On the basis of archival, interferometric and single-dish radio data, we have determined the radio spectrum of an elliptical region around the Galactic centre of extent 3 degrees semi-major axis (along the Galactic plane) and 1 degree semi-minor axis and a second, rectangular region, also centered on the GC, of extent 1.6 degrees x 0.6 degrees. The radio spectra of both regions are non-thermal over the range of frequencies for which we have data: 74 MHz -- 10 GHz. We also consider gamma-ray data covering the same region from the EGRET instrument (about GeV) and from HESS (around TeV). We show how the combination of these data can be used to place robust constraints on DM annihilation scenarios, in a way which is relatively insensitive to assumptions about the magnetic field amplitude in this region. Our results are approximately an order of magnitude more constraining than existing Galactic centre radio and gamma ray limits. For a DM mass of m_χ=10 GeV, and an NFW profile, we find that the velocity-averaged cross-section must be less than a few times 10^-25 cm^3 s^-1.
An excess in $γ$-rays emanating from the galactic centre has recently been observed in the Fermi-LAT data. We investigate the new exciting possibility of fitting the signal spectrum by dark matter annihilating dominantly to a Higgs-pseudoscalar pair. We show that the fit to the $γ$-ray excess for the Higgs-pseudoscalar channel can be just as good as for annihilation into bottom-quark pairs. This channel arises naturally in a full model such as the next-to-minimal supersymmetric Standard Model (NMSSM) and we find regions where dark matter relic density, the $γ$-ray signal and other experimental…
In this paper, we will discuss a specific case that the dark matter particles annihilate into right-handed neutrinos. We calculate the predicted gamma-ray excess from the galactic center and compare our results with the data from the Fermi-LAT. An approximately 10-60 GeV right-handed neutrino with heavier dark matter particle can perfectly explain the observed spectrum. The annihilation cross section $\langle σv \rangle$ falls within the range $0.5$-$4 \times 10^{-26} \text{ cm}^3/\text{s}$, which is roughly compatible with the WIMP annihilation cross section.
Gamma-ray Constraints on Dark Matter Annihilation into Charged Particles
暗物质湮灭成为带电粒子必然伴随着伽马射线，通过辐射校正产生。来自末态粒子的内部韧致辐射可以产生硬伽马射线，直到暗物质质量，具有近似与模型无关的光谱。专注于湮灭成电子，我们计算强大的上限上的暗物质自湮灭截面$<σ_A v >_{e^+e^-}$使用伽马射线数据从银河系跨越广泛的能量，$\sim10^{-3} - 10^4$ GeV。我们还计算了其他带电轻子相应的边界。我们保守的假设，天体物理的输入，并证明我们的推导出的界限将得到加强，如果更强的假设，这些输入。在与$e^+e^-$湮灭相伴的终点附近，硬伽马射线的比例仅比直接湮灭为单能伽马射线的情况低$\alt 10^2$的一个因子。因此，$<σ_A v >_{e^+e^-}$上的结合比$<σ_A v >_{γγ}$上的结合弱相同的因子。带电轻子湮灭截面的上限与中微子定义的{ \it总}湮灭截面的上限进行了比较。
We consider the angular distribution of the photon signal which could arise from velocity-dependent dark matter annihilation within the Galactic bulge. We find that, for the case of Sommerfeld-enhanced annihilation, dark matter annihilation within the bulge is dominated by slow speed particles which never leave the bulge, allowing one to find a simple analytic relationship between the dark matter profile within the Galactic bulge and the angular distribution. On the other hand, for the case $p$- or $d$-wave annihilation, we find that the small fraction of high-speed particles which can leave t…
Diffuse Gamma Rays from WIMP Decay and Annihilation
我讨论了弱相互作用大质量粒子（WIMPs）的衰变和湮灭对漫射伽马射线背景的贡献。首先回顾了WIMP的宇宙学丰度的计算，并指出它与WIMP湮灭成较轻粒子的截面简单相关。讨论了WIMP衰变产生的河外背景辐射。我展示了如何观测上限的DEBRA可以用来约束衰减到光子的WIMP的属性，我提出了额外的新的约束，湮灭截面的酉性强加在这样的粒子。然后，我讨论伽马射线湮灭的弱相互作用粒子在晕，球状体，和磁盘的我们的星系，以及那些从弱相互作用粒子湮灭在大麦云云。(To出现在The Gamma Ray Sky with Compton GRO and SIGMA，Proceedings of the School，Les Houches，France，January 25-February 4，1994中。
The very large (100-1000) mass-to-light ratio applicable to the ultra-faint dwarf galaxies (UFDs) implies a high concentration of dark matter, thus rendering them ideal theatres for indirect signatures of dark matter. In this paper, we consider 14 recently discovered UFDs and study the electromagnetic radiation emanating from them over a wide range, from gamma ray down to radio frequencies. We analyze the Fermi-LAT data on high energy gamma rays and radio fluxes at the GMRT and VLA to obtain upper limits on annihilation cross section $\langleσv\rangle$ in a model independent way. We further di…
Hadron annihilation into two photons and backward dVCS in the scaling regime of QCD
我们研究了强子-（反）-强子湮灭为深虚光子和实光子（H anti-H -> gamma^* gamma）以及深后向虚康普顿散射（gamma^* H -> H gamma）的标度机制。我们主张存在一个运动学区域，在这个区域中，散射振幅分解为一个短距离矩阵元和一个长距离支配体：描述强子到光子跃迁的跃迁分布振幅。
We investigate the relation between the annihilation of dark matter (DM) particles into lepton pairs and into 2-body final states including one or two photons. We parametrize the DM interactions with leptons in terms of contact interactions, and calculate the loop-level annihilation into monochromatic gamma rays, specifically computing the ratio of the DM annihilation cross sections into two gamma rays versus lepton pairs. While the loop-level processes are generically suppressed in comparison with the tree-level annihilation into leptons, we find that some choices for the mediator spin and co…
In this work we study the constraints on dark matter (DM) annihilation/decay from the Fermi-LAT Isotropic Gamma-Ray Background (IGRB) observation. We consider the contributions from both extragalactic and galactic DM components. For DM annihilation, the evolutions of extragalactic DM halos are taken into account. We find that the IGRB constraints under some DM subhalo models can be comparable to those derived from the observations of dwarf spheroidal galaxies. We also use the IGRB results to constrain the parameter regions accounting for the latest AMS-02 electron-positron anomaly. We find tha…
We incorporate Milky Way dark matter halo profile uncertainties, as well as an accounting of diffuse gamma-ray emission uncertainties in dark matter annihilation models for the Galactic Center Extended gamma-ray excess (GCE) detected by the Fermi Gamma Ray Space Telescope. The range of particle annihilation rate and masses expand when including these unknowns. However, two of the most precise empirical determinations of the Milky Way halo's local density and density profile leave the signal region to be in considerable tension with dark matter annihilation searches from combined dwarf galaxy a…
In this paper, we explore the possibility of a linearly polarized gamma-ray signal from dark matter annihilations in the Galactic center. Considering neutral weakly interacting massive particles, a polarized gamma-ray signal can be realized by a two-component dark matter model of Majorana fermions with an anapole moment. We discuss the spin alignment of such dark matter fermions in the Galactic center and then estimate the intensity and the polarizability of the final-state electromagnetic radiation in the dark matter annihilations. For low-mass dark matter, the photon flux at sub-GeV energies…
We investigate the possibility of the Z3 scalar singlet model explaining the Fermi galactic centre excess. We find a good fit to the measured spectral excess in the region where the dark matter mass is comparable to the Higgs and the Higgs portal coupling $λ_{HS}\sim 0.04$. This preferred region is consistent with constraints from vacuum stability and current dark matter experiments, and will be discovered or falsified soon by future dark matter direct detection experiment.
