Dwarf Galaxy $γ$-excess and 3.55 keV X-ray Line In A Nonthermal Dark Matter Model
Anirban Biswas, Debasish Majumdar, Probir Roy
备注：
8 eps figures, 1 Table, 7 pages. The paper has been completely rewritten with additional references and discussions of indirect constraints from AMS-02 and ANTARES data. Basic results remain unchanged. Version accepted for publication in Europhysics Letters
Recent data from Reticulum II (RetII) require the energy range of the FermiLAT $γ$-excess to be $\sim$ $2-10$ GeV. We adjust our unified nonthermal Dark Matter (DM) model to accommodate this. We have two extra scalars beyond the Standard Model to also explain 3.55 keV X-ray line. Now the mass of the heavier of them has to be increased to lie around 250 GeV, while that of the lighter one remains at 7.1 keV. This requires a new seed mechanism for the $γ$-excess and new Boltzmann equations for the generation of the DM relic density. All concerned data for RetII and the X-ray line can now be fitted well and consistency with other indirect limits attained.
The excess of the 511 keV line from the Milky Way galactic bulge, confirmed by the INTEGRAL detector, is a longstanding mystery. The morphology of the line appears to be proportional to the square of the dark matter density, hinting towards a dark matter origin. On the other hand, in 2020, XENON1T has reported an excess of electrons with a recoil energy of $2-4$ keV. We present a model based on a dark matter of a few MeV mass that decays into a pair of pico-charged particles with a lifetime much larger than the age of the Universe. The magnetic field of the galaxy accumulates these relativisti…
In this paper we introduce a light Dirac particle $ψ$ as thermal dark matter candidate in a $U(1)_{L_μ-L_τ}$ model. Together with the new gauge boson $X$, we find a possible parameter space with $m_X \simeq 20$ MeV, $U(1)_{L_μ-L_τ}$ coupling $g_X \simeq 5 \cdot 10^{-4}$ and $m_ψ\gtrsim m_X/2$ where the $(g-2)_μ$ anomaly, dark matter, the Hubble tension, and (part of) the excess of $511$ keV photons from the region near the galactic center can be explained simultaneously. This model is safe from current experimental and astrophysical constraints, but can be probed by the next generation of neut…
We propose a quasi-degenerate dark matter scenario to simultaneously explain the $1.4\,\textrm{TeV}$ peak in the high-energy cosmic-ray electron-positron spectrum reported by the DAMPE collaboration very recently and the $3.5\,\textrm{keV}$ X-ray line observed in galaxies clusters and from the Galactic centre and confirmed by the Chandra and NuSTAR satellites. We consider a dark $SU(2)'\times U(1)'$ gauge symmetry under which the dark matter is a Dirac fermion doublet composed of two $SU(2)'$ doublets with non-trivial $U(1)'$ charges. At one-loop level the two dark fermion components can have …
We provide updates to the limits on solar emission of dark photons, or more generally any light vector particle coupled to the electron vector current. The recent 2019 and 2020 electronic recoil data from XENON1T now provides more stringent constraints on these models than stellar energy loss in the sub-keV mass region. We also show that solar emission of dark photons does not provide a good fit to the recent XENON1T excess in the 2-5 keV energy bins. In contrast, the absorption of 2-4 keV mass dark photons that saturate the local dark matter mass density does provide a good fit to the excess,…
Freeze-in dark matter (DM) mediated by a light ($\ll$ keV) weakly-coupled dark-photon is an important benchmark for the emerging low-mass direct detection program. Since this is one of the only predictive, detectable freeze-in models, we investigate how robustly such testability extends to other scenarios. For concreteness, we perform a detailed study of models in which DM couples to a light scalar mediator and acquires a freeze-in abundance through Higgs-mediator mixing. Unlike dark-photons, whose thermal properties weaken stellar cooling bounds, the scalar coupling to Standard Model (SM) par…
In the scenario with a multiplicity of sectors which independently break supersymmetry, multiplicity of goldstini are predicted. We propose a new interpretation of the electron recoil excess at 2-7 keV observed in the XENON1T experiment with very long-lived goldstini DM elastically scattering off the electrons. The goldstini DM can be boosted by the late-decay of the other nearly degenerate (long-lived) goldstini DM, with their tiny mass difference being converted into kinetic energy of the lighter goldstini DM and neutrinos. We show that viable parameter space can be found which can explain t…
There have been several reports of a detection of an unexplained excess of X-ray emission at $\simeq$ 3.5 keV in astrophysical systems. One interpretation of this excess is the decay of sterile neutrino dark matter. The most influential study to date analysed 73 clusters observed by the XMM-Newton satellite. We explore evidence for a $\simeq$ 3.5 keV excess in the XMM-PN spectra of 117 redMaPPer galaxy clusters ($0.1 < z < 0.6$). In our analysis of individual spectra, we identify three systems with an excess of flux at $\simeq$ 3.5 keV. In one case (XCS J0003.3+0204) this excess may result fro…
We study scalar and fermionic crossing two-component dark matter (C2CDM) models with $ U(1)_X $ dark gauge symmetry. This $ U(1)_X $ gauge symmetry is broken via the dark Higgs mechanism of a dark Higgs field $Φ$ and the dark photon becomes massive. On the other hand, the same dark Higgs field $Φ$ also serves as a bridge between each component of two DM sectors such that the dark flavor-changing neutral current (DFCNC) interaction between them is induced. Moreover, the mass splitting between these two DM sectors is generated after $ U(1)_X $ gauge symmetry breaking by nonzero $\langle Φ\rangle…
We propose boosted dark matter (BDM) as a possible explanation for the excess of keV electron recoil events observed by XENON1T. BDM particles have velocities much larger than those typical of virialized dark matter, and, as such, BDM-electron scattering can naturally produce keV electron recoils. We show that the required BDM-electron scattering cross sections can be easily realized in a simple model with a heavy vector mediator. Though these cross sections are too large for BDM to escape from the Sun, the BDM flux can originate from the Galactic Center or from halo dark matter annihilations.…
The XENON1T dark matter experiment recently reported 0.65 ton-year exposure measurement on electron recoils , which shows an excess in $2\sim 3$ KeV recoils above the detector background. In this paper we present a Pseudo-Dirac dark matter scenario to explain the excess via inelastic dark matter-electron scattering. With a KeV scale mass splitting between the two components of the Pseudo-Dirac dark matter, the slightly excited component can down-scatter on electrons. The desired dark matter masses are about 10 GeV with a 4 KeV mass-splitting and unity coupling to electrons, which generate the …
An excess of 511 keV photons has been detected from the central region of the Milky Way. It has been suggested that the positrons responsible for this signal could be produced through the Hawking evaporation of primordial black holes. After evaluating the constraints from INTEGRAL, COMPTEL, and Voyager 1, we find that black holes in mass range of $\sim(1-4)\times10^{16}$ g could potentially produce this signal if they make up a small fraction of the total dark matter density. Proposed MeV-scale gamma-ray telescopes such as AMEGO or e-ASTROGAM should be able to test this class of scenarios by m…
\emph{Hitomi} observations of Perseus with the Soft X-ray Spectrometer (SXS) provide a high-resolution look at the 3.5 keV feature reported by multiple groups in the Perseus cluster. The \emph{Hitomi} spectrum -- which involves the sum of diffuse cluster emission and the point-like central Active Galactic Nucleus (AGN) -- does not show any excess at $E \sim 3.5 {\rm keV}$, giving an apparent inconsistency with previous observations of excess diffuse emission. We point out that 2009 \emph{Chandra} data reveals a strong dip in the AGN spectrum at $E = (3.54 \pm 0.02) {\rm keV}$ (cluster frame) -…
Motivated by the recent excess in the electron recoil from XENON1T experiment, we consider the possibility of exothermic dark matter, which is composed of two states with mass splitting. The heavier state down-scatters off the electron into the lighter state, making an appropriate recoil energy required for the Xenon excess even for the standard Maxwellian velocity distribution of dark matter. Accordingly, we determine the mass difference between two component states of dark matter to the peak electron recoil energy at about $2.5\,{\rm keV}$ up to the detector resolution, accounting for the re…
The XENON1T excess of keV electron recoil events may be induced by the scattering of electrons and long-lived particles with MeV mass and high-speed. We consider a tangible model composed of two scalar MeV dark matter (DM) particles $S_A$ and $S_B$ to interpret the XENON1T keV excess via boosted $S_B$. A small mass splitting $m_{S_A}-m_{S_B}>0$ is introduced and the boosted $S_B$ can be produced by the dark annihilation process of $S_A S_A^\dagger \to ϕ\to S_B S_B^\dagger$ via a resonant scalar $ϕ$. The $S_B-$electron scattering is intermediated by a vector boson $X$. Although the constraints …
In the light of the recently observed XENON1T electronic recoil (ER) data, we investigate the possibility of constraining the parameter space of a generic fermionic warm dark matter (WDM), decaying into a standard model (SM) neutrino and a photon. The photon as a decay product, when produced inside the XENON1T chamber, interacts with an electron of a xenon (Xe) atom, leading to a contribution in the observed ER data. We add this dark matter (DM) induced signal over the standard background ($\rm B_0$) considered by the XENON1T collaboration and perform a $χ^2$ fit against the XENON1T data to ob…
Motivated by the recent XENON1T results, we explore various new physics models that can be discovered through searches for electron recoils in O(keV)-threshold direct-detection experiments. First, we consider the absorption of light bosons, either as dark matter relics or being produced directly in the Sun. In the latter case, we find that keV mass bosons produced in the Sun provide an adequate fit to the data but are excluded by stellar cooling constraints. We address this tension by introducing a novel Chameleon-like axion model, which can explain the excess while evading the stellar bounds.…
The identity of dark matter is being sought with increasingly sensitive and voluminous underground detectors. Recently the XENON1T collaboration reported excess electronic recoil events, with most of these having recoil energies around $1-30$ keV. We show that a straightforward model of inelastic dark matter produced via early universe thermal freeze-out annihilation can account for the XENON1T excess. Remarkably, this dark matter model consists of a few simple elements: sub-GeV mass Dirac fermion dark matter coupled to a lighter dark photon kinetically mixed with the Standard Model photon. A …
A scalar-extended ${\rm U(1)_{L_μ-L_τ}}$ explanation of the LUX-ZEPLIN 248 keV excess
Institute of Physics（印度物理研究所）；Homi Bhabha National Institute, BARC Training School Complex（霍米·巴巴国立学院，BARC培训学院）；Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-Alpes, CNRS/IN2P3（法国格勒诺布尔阿尔卑斯大学亚原子物理与宇宙学实验室）
PandaX-II has analyzed their complete data set of the electron recoil energy spectrum and has confirmed the XENON1T (1-7) keV excess, although the excess was also found compatible with the total background. Treating the background as well known, in which case it provides a good fit to the observed spectrum, one can expect stronger constraints on any new physics model with this data. With this motivation, we derive constraints on the new general vector (V), axial-vector (A), scalar (S) and pseudoscalar (P) interactions if any of them contribute to the neutrino-electron elastic scattering. The d…
