We scrutinize the XENON1T electron recoil excess in the scalar-singlet-extended dark matter effective field theory. We confront it with various astrophysical and laboratory constraints both in a general setup and in the more specific, recently proposed, variant with leptophilic $Z_2$-odd mediators. The latter also provide mass to the light leptons via suppressed $Z_2$ breaking, a structure that is well fitting with the nature of the observed excess and the discrete symmetry leads to non-standard dark-matter interactions. We find that the excess can be explained by neutrino--electron interactions, linked with the neutrino and electron masses, while dark-matter--electron scattering does not lead to statistically significant improvement. We analyze the parameter space preferred by the anomaly and find severe constraints that can only be avoided in certain corners of parameter space. Potentially problematic bounds on electron couplings from Big-Bang Nucleosynthesis can be circumvented via a late phase transition in the new scalar sector.
Measuring dark matter (DM) signals via electron recoil provides an important means for direct detection of light DM particles. The recent XENON1T anomaly with electron recoil energy around $\,E_R^{}\!=\!(2-3)$keV can be naturally explained by DM inelastic scattering which injects energy to the recoiled electrons and gives a narrow peak structure in the recoil spectrum. We present an effective field theory (EFT) approach to exothermic inelastic DM signals for the Xenon electron recoil detection. For relatively heavy mediator, we fairly formulate the DM-lepton interactions by effective contact o…
The XENON1T collaboration recently reported an excess in electron recoil events in the energy range between $1-7\,\mathrm{keV}$. This excess could be understood to originate from the known solar neutrino flux, if neutrinos couple to a light vector-mediator with strength $g_{νN}$ that kinetically mixes with the photon with strength $χ$, and $g_{νN}χ\sim10^{-13}$. Here, we show that such coupling values can naturally arise in a renormalizable model of long-range vector-mediated neutrino self-interactions. The model could be discriminated from other explanations of the XENON1T excess by the chara…
For the low-energy anti-neutrino reaction, $\barν_e + p \to e^+ + n$, which is of great current interest in connection with on-going high-precision neutrino-oscillation experiments, we calculate the differential cross section in a model-independent effective field theory (EFT), taking into account radiative corrections of order $α$. In EFT, the short-distance radiative corrections are subsumed into well-defined low-energy constants the values of which can in principle be determined from the available neutron beta-decay data. In our low-energy EFT, the order-$α$ radiative corrections are consid…
LZ Nuclear-Recoil Excess from Boosted Light Magnetic Dipole-dipole Dark Matter
Wuyi University（五邑大学）；Nanjing University（南京大学）；National Taiwan University（台湾大学）；Phenikaa University（菲尼亚卡大学）；University of Oslo（奥斯陆大学）；University of California, Los Angeles（加州大学洛杉矶分校）
The XENON1T experiment has recently announced the observation of an excess in electron recoil events at energy range of $1-7$ keV with a $3.5~σ$ signal significance over the Standard Model prediction. In this letter we sketch the prospects of explaining such an excess from Migdal ionization events with below threshold nuclear recoil energies. Interestingly, these are expected to show signal events in the ballpark energy scale of the observed excess. We demonstrate that the observed signal can be reproduced through the Migdal effect by an $\mathcal{O}(1)$ GeV neutron-philic dark matter having a…
We show that the electron recoil excess around 2 keV claimed by the Xenon collaboration can be fitted by DM or DM-like particles having a fast component with velocity of order $\sim 0.1$. Those particles cannot be part of the cold DM halo of our Galaxy, so we speculate about their possible nature and origin, such as fast moving DM sub-haloes, semi-annihilations of DM and relativistic axions produced by a nearby axion star. Feasible new physics scenarios must accommodate exotic DM dynamics and unusual DM properties.
An excess of events of unknown origin at low energies below 1 keV has been observed in multiple low-threshold dark matter detectors. Depending on the target material, nuclear recoil events at these energies may cause lattice defects, in which case a part of the true recoil energy is stored in the defect and not observed in the phonon detector. If the threshold for defect creation is sharp, this effect leads to a prominent feature in the observed recoil spectrum. Electronic recoils at low energies do not create defects and therefore the feature in the observed spectrum is not expected in that c…
We show that electron recoils induced by non-relativistic Dark Matter interactions can fit well the recently reported Xenon1T excess, if they are mediated by a light pseudo-scalar in the MeV range. This is due to the favorable momentum-dependence of the resulting scattering rate, which partially compensates the unfavorable kinematics that tends to strongly suppress keV electron recoils. We study the phenomenology of the mediator and identify the allowed parameter space of the Xenon1T excess which is compatible with all experimental limits. We also find that the anomalous magnetic moments $(g-2…
We consider the diphoton excess observed by ATLAS and CMS using the most up-to-date data and estimate the preferred enhancement in the production rate between 8 TeV and 13 TeV. Within the framework of effective field theory (EFT), we then show that for both spin-0 and spin-2 Standard Model (SM) gauge-singlet resonances, two of the three processes S to ZZ, S to Z gamma, and S to WW must occur with a non-zero rate. Moreover, we demonstrate that these branching ratios are highly correlated in the EFT. Couplings of S to additional SM states may be constrained and differentiated by comparing the S …
Recently, the XENON1T experiment has reported the possible detection of an excess in the electronic recoil spectrum. Such an excess may indicate the presence of new physics. In this work, we suggest that the scattering of mirror electrons with ordinary electrons through photon$-$mirror photon kinetic mixing with parameter $ε\sim 10^{-12}(n_{\rm e'}/0.2{\rm cm^{-3}})^{-1/2}({v_{\rm c}^0/5\times 10^{9}~{\rm cm~s^{-1}}})^{1/2}$ may account for the excess electronic recoil events in XENON1T, where $n_{\rm e'}$ is the density of mirror electron and $v_{\rm c}^0$ is the cutoff velocity of the mirror…
Distinguishing a dark matter interaction from an astrophysical neutrino-induced interaction will be major challenge for future direct dark matter searches. In this paper, we consider this issue within non-relativistic Effective Field Theory (EFT), which provides a well-motivated theoretical framework for determining nuclear responses to dark matter scattering events. We analyze the nuclear energy recoil spectra from the different dark matter-nucleon EFT operators, and compare to the nuclear recoil energy spectra that is predicted to be induced by astrophysical neutrino sources. We determine th…
Detection of electron recoils by dark matter (DM) may reveal the structure of the dark sector. We consider a scenario where a heavier DM particle inelastically scatters off an electron and is converted into a lighter DM particle. A small mass difference between the two DM particles is transferred into electron recoil energy. We investigate the DM-electron interaction mediated by a massive dark photon and evaluate the inelastic DM scattering rate, taking account of the atomic structure. It is found that the scattering rate is significantly enhanced because of the small mass splitting, which all…
We consider a novel mechanism to realize exothermic dark matter with dark mesons in the limit of approximate flavor symmetry in a dark QCD. We introduce a local dark $U(1)'$ symmetry to communicate between dark mesons and the Standard Model via $Z'$ portal by partially gauging the dark flavor symmetry with flavor-dependent charges for cancelling chiral anomalies in the dark sector. After the dark local $U(1)'$ is broken spontaneously by the VEV of a dark Higgs, there appear small mass splittings between dark quarks, consequently, leading to small split masses for dark mesons, required to expla…
The dark matter interpretation for a recent observation of excessive electron recoil events at the XENON1T detector seems challenging because its velocity is not large enough to give rise to recoiling electrons of $\mathcal{O}({\rm keV})$. Fast-moving or boosted dark matter scenarios are receiving attention as a remedy for this issue, rendering the dark matter interpretation a possibility to explain the anomaly. We investigate various scenarios where such dark matter of spin 0 and 1/2 interacts with electrons via an exchange of vector, pseudo-scalar, or scalar mediators. We find parameter valu…
In the past few years, the interest to collider searches for direct dark matter (DM) production has been growing exponentially. A variety of "Mono-X" signatures have been considered, where X stands for a probe particle recoiling against DM particles, which allows for the event to be triggerable. So far, the analysis of these signatures has been largely carried out in the framework of effective field theory (EFT), which allows for a comparison of the collider searches with searches in direct detection experiments. Unfortunately, as it has been recently pointed out by a number of authors, the EF…
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 collaboration has observed an excess in electronic recoil events below $5~\mathrm{keV}$ over the known background, which could originate from beyond-the-Standard-Model physics. The solar axion is a well-motivated model that has been proposed to explain the excess, though it has tension with astrophysical observations. The axions traveled from the Sun can be absorbed by the electrons in the xenon atoms via the axion-electron coupling. Meanwhile, they can also scatter with the atoms through the inverse Primakoff process via the axion-photon coupling, which emits a photon and mimics t…
We propose a decaying cold dark matter model to explain the excess of electron recoil observed at the XENON1T experiment. In this scenario, the daughter dark matter from the parent dark matter decay easily obtains velocity large enough to saturate the peak of the electron recoil energy around 2.5 keV, and the observed signal rate can be fulfilled by the parent dark matter with a mass of order 10-200 MeV and a lifetime larger than the age of Universe. We verify that this model is consistent with experimental limits from dark matter detections, Cosmic Microwave Background and Large Scale Structu…
The XENON1T collaboration reported an excess of the low-energy electron recoil events between 1 and 7 keV. We explore the possibility to explain such an anomaly by the MeV-scale dark matter (DM) heated by the interior of the Sun due to the same DM-electron interaction as in the detector. The kinetic energies of heated DM particles can reach a few keV, and can potentially account for the excess signals detected by XENON1T. We study different form factors of the DM-electron interactions, $F(q)\propto q^i$ with $i=0,1,2$ and $q$ being the momentum exchange, and find that for all these cases the i…
The recent Xenon1T excess can be explained by solar neutrino scattering with electron via a light mediator, either scalar or vector, in addition to many other explanations from the dark sector. Since only the recoil electron is observable, a keV sterile neutrino instead of an active neutrino can appear in the final state. The sterile neutrino allows pseudoscalar mediator to explain the Xenon1T excess which was thought impossible. In addition, nonzero recoil energy lower bound arises from the sterile neutrino mass, which can be used to testify if the sterile neutrino is massive or not. We also …
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…
In 2020 the XENON1T experiment observed an excess of events with an electron recoil energy $E_R$ in the range of $2\,$--$\,3\,$keV. Such an excess can arise from a variety of sources such as solar axions or a neutrino magnetic moment, but also from inelastic scattering of dark matter off the xenon atoms. The recoil energy of the electron then depends on the mass difference of the dark particles. In this paper we show that the annual modulation of both the event rate and the electron recoil energy provide important additional information that allows to distinguish among different theoretical ex…
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 …
We consider the boosted dark matter solution of the XENON1T excess to constrain the framework through loop-generated processes. The interaction of the boosted dark matter component, which sources the signal, effectively couples the cold dark matter background to the electrons, making it potentially visible in the electron recoil searches. Similarly, once the radiative corrections due to the Standard Model are taken into account, dark matter also scatters on quarks and becomes observable in nuclear recoil measurements. By analysing these processes, we find that the current direct detection cons…
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…
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 re…
The phenomenological model with three active and three sterile neutrinos is used for interpretation of the observed XENON1T excess of electronic recoil events in the 1 -- 7 keV energy region. Assuming two sterile neutrinos with appropriate mass values decay while the third sterile neutrino is stable it is possible to explain the observed energy spectrum of electronic recoil events. Moreover using this approach three peaks in the 1 -- 7 keV energy region are predicted. Dark bosons have to mix to only a small extent with photons which can be emitted in this region. The possible existence of the …
We carry out a series of studies on pion and photon productions in neutrino/electron/photon--nucleus scatterings. The low energy region is investigated by using a chiral effective field theory for nuclei. The results for the neutral current induced photon production ($γ$-NCP) are then extrapolated to neutrino energy $E_ν\sim$ GeV region. By convoluting the cross sections with MiniBooNE's beam spectrum and detection efficiency, we estimate its $γ$-NCP, event number, and conclude that such photon production can not fully explain its low energy event excess in both neutrino and antineutrino runs.
Recently, the XENON1T experiment has observed an excess in the electronic recoil data in the recoil energy range of $1$-$7$ keV. One of the most favored new physics interpretations is electron scattering with a boosted particle with a velocity of $\sim 0.1$ and a mass of $\gtrsim 0.1\,\mathrm{MeV}$. If such a particle has a strong interaction with electrons, it may affect the standard scenario of cosmology or be observed at low-threshold direct detection experiments. We study various constraints, mainly focusing on those from the big-bang nucleosynthesis, supernova cooling, and direct detectio…
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 …
Inelastic Dark Matter and High-Energy Recoil Signatures in LZ
Department of Physics, Tsinghua University（清华大学物理系）；Center for High Energy Physics, Peking University（北京大学高能物理中心）；Department of Physics and Jockey Club Institute for Advanced Study, The Hong Kong University of Science and Technology（香港科技大学物理系及赛马会高等研究院）
Probing the Dark Matter EFT with QUEST-DMC: Projected Sensitivities and Attenuation Ceilings
Royal Holloway University of London（伦敦大学皇家霍洛威学院）；Lancaster University（兰卡斯特大学）；University of Oxford（牛津大学）；University of Liverpool（利物浦大学）；RIKEN（理化学研究所）；UKRI STFC Rutherford Appleton Laboratory（英国研究与创新部科学和技术设施委员会鲁瑟福阿普尔顿实验室）
We present a particle physics model to explain the observed enhancement in the Xenon-1T data at an electron recoil energy of 2.5 keV. The model is based on a $U(1)$ extension of the Standard Model where the dark sector consists of two essentially mass degenerate Dirac fermions in the sub-GeV region with a small mass splitting interacting with a dark photon. The dark photon is unstable and decays before the big bang nucleosynthesis, which leads to the dark matter constituted of two essentially mass degenerate Dirac fermions. The Xenon-1T excess is computed via the inelastic exothermic scatterin…
We show that the excess in electron recoil events seen by the XENON1T experiment can be explained by relatively low-mass Luminous Dark Matter candidate. The dark matter scatters inelastically in the detector (or the surrounding rock), to produce a heavier dark state with a ~2.75 keV mass splitting. This heavier state then decays within the detector, producing a peak in the electron recoil spectrum which is a good fit to the observed excess. We comment on the ability of future direct detection datasets to differentiate this model from other Beyond the Standard Model scenarios, and from possible…
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 recently reported excess in XENON1T is explained by new leptonic forces, which are free from gauge anomalies. We focus on two scenarios with and without dark matter. In Scenario #1, the gauge boson of gauged lepton number U(1)$_{L_e-L_j}$, $j=μ$ or $τ$ provides non-standard interaction between solar neutrino and electron that enhances the number of electron recoil events in the XENON1T detector. In Scenario #2, the new gauge boson exclusively couples to electron and dark matter, then cosmic-ray electrons can transfer their momenta to dark matter in halo. The boosted dark matter generates t…
We propose models of Dark Matter that account for the 511 keV photon emission from the Galactic Centre, compatibly with experimental constraints and theoretical consistency, and where the relic abundance is achieved via p-wave annihilations or, in inelastic models, via co-annihilations. Due to the Dark Matter component that is inevitably upscattered by the Sun, these models generically predict keV electron recoils at detectors on Earth, and could naturally explain the excess recently reported by the XENON1T collaboration. The very small number of free parameters make these ideas testable by de…
A gluphilic scalar dark matter (GSDM) model has recently been proposed as an interesting vision for WIMP dark matter communicating dominantly with the Standard Model via gluons. We discuss the collider signature of a hard jet recoiling against missing momentum ("mono-jet") in such a construction, whose leading contribution is at one-loop. We compare the full one-loop computation with an effective field theory (EFT) treatment, and find (as expected) that EFT does not accurately describe regions of parameter space where mass of the colored mediator particles are comparable to the experimental cu…
The growing interest in the interactions between dark matter particles and electrons has received a further boost by the observation of an excess in electron recoil events in the XENON1T experiment. Of particular interest are dark matter models in which the scattering process is inelastic, such that the ground state can upscatter into an excited state. The subsequent exothermic downscattering of such excited states on electrons can lead to observable signals in direct detection experiments and gives a good fit to the XENON1T excess. In this work, we study terrestrial upscattering, i.e. inelast…
Very recently, the Xenon1T collaboration has reported an intriguing electron recoil excess, which may imply for light dark matter. In order to interpret this anomaly, we propose the atmospheric dark matter (ADM) from the inelastic collision of cosmic rays (CRs) with the atmosphere. Due to the boost effect of high energy CRs, we show that the light ADM can be fast-moving and successfully fit the observed electron recoil spectrum through the ADM-electron scattering process. Meanwhile, our ADM predicts the scattering cross section $σ_e \sim {\cal O}(10^{-38}- 10^{-39}$) cm$^{2}$, and thus can eva…
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…
Previous work has argued that the DAMA annual modulation signal might be due to electron recoils in plasma dark matter models. A specific model assuming mirror dark matter and featuring collisional shielding of a detector due to Earth-bound dark matter was put forward by this author [arXiv:1806.04293]. That explanation predicted a low energy electron recoil signal in the XENON1T experiment. In light of the excess of electron recoils observed in XENON1T, we re-examine that model's predictions for both DAMA and XENON1T.
This work is a study of some possible background sources in the XENON1T environment which might affect the energy spectrum of electronic recoil events in the lower side and might contribute to the observed excess. We have identified some additional possible backgrounds, like $^{41}$Ca, $^{49}$V, $^{63}$Ni, $^{106}$Ru and $^{125}$Sb coming from cosmogenic production, where the former two emit monoenergetic $X$-rays and the latter three have $β$ decays, or isotopes, like $^{210}$Pb, from the decay chain of $^{222}$Rn emanated in liquid xenon from the materials, or isotopes, like $^{137}$Cs, prod…
The recently reported result from XENON1T experiment indicates that there is an excess with $3.5σ$ significance in the electronic recoil events. Interpreted as new physics, new sources are needed to account for the electronic scattering. We show that a dark fermion $ψ$ with mass about $ \mathcal{O}\left(10\right)$ MeV from semi-annihilation of $Z_3$ dark matter $X$ and subsequent decay of a dark gauge boson $V_μ$ may be responsible for the excess. The relevant semi-annihilation process is $X+X\rightarrow \overline{X}+V_μ(\rightarrow ψ+ \overlineψ)$, in which the final $ψ$ has a box-shape energ…
We perform a constrained spectral fit analysis of the excess observed in the electron recoil energy spectrum by XENON1T with neutrino magnetic moment, charge radius, neutrino millicharge and new light vector and scalar mediators. Within the limits allowed by other laboratory experiments we find that the excess can be explained in the range$\ (2-4)\times 10^{-11}μ_{B} $ for the magnetic moment,$\ (2-6)\times 10^{-31}$cm$^{2}$ for the charge radius, $\ (1.7-2.3)\times 10^{-12}e$ for the millicharge and $(10-100)\ $keV masses of light mediators with couplings of $ 3.5\times 10^{-7}$ for vector/ax…
We discuss some consistency tests that must be passed for a successful explanation of a diphoton excess at larger mass scales, generated by a scalar or pseudoscalar state, possibly of a composite nature, decaying to two photons. Scalar states at mass scales above the electroweak scale decaying significantly into photon final states generically lead to modifications of Standard Model Higgs phenomenology. We characterise this effect using the formalism of Effective Field Theory (EFT) and study the modification of the effective couplings to photons and gluons of the Higgs. The modification of Hig…
CRESST is a direct dark matter search experiment, aiming for an observation of nuclear recoils induced by the interaction of dark matter particles with cryogenic scintillating calcium tungstate crystals. Instead of confining ourselves to standard spin-independent and spin-dependent searches, we re-analyze data from CRESST-II using a more general effective field theory (EFT) framework. On many of the EFT coupling constants, improved exclusion limits in the low-mass region (< 3-4 GeV) are presented.
We analyze future direct data matter detection experiments using Effective Field Theory (EFT) operators with light, $\lesssim 100$ MeV mass mediators. We compare the nuclear recoil energy spectra from these operators to the predicted high energy solar neutrino spectrum. A set of operators that generate spectra similar to the neutrino background is identified, however this set is distinct from those that mimic the neutrino background for heavy, $\gtrsim 100$ MeV mass mediators. We outline a general classification scheme based on momentum dependence of the dark matter-nucleus interaction to dete…
Can Nuclear Recoils and Solar Neutrinos Resolve the Composition of Singlino-Higgsino Dark Matter?
Henan Institute of Science and Technology（河南科技学院）；Henan Normal University（河南师范大学）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）
Recently XENON1T Collaboration announced that they observed some excess in the electron recoil energy around a 2-3 keV. We show that this excess can be interpreted as exothermic scattering of excited dark matter (XDM), $XDM + e_{atomic} \rightarrow DM + e_{free}$ on atomic electron through dark photon exchange. We consider DM models with local dark $U(1)$ gauge symmetry that is spontaneously broken into its $Z_2$ subgroup by Krauss-Wilczek mechanism. In order to explain the XENON1T excess with the correct DM thermal relic density within freeze-out scenario, all the particles in the dark sector…
We present a dark matter model to explain the excess events in the electron recoil data recently reported by the Xenon1T experiment. In our model, dark matter $χ$ annihilates into a pair of on-shell particles $ϕ$ which subsequently decay into $ψψ$ final state; $ψ$ interacts with electron to generate the observed excess events. Due to the mass hierarchy, the velocity of $ψ$ can be rather large and can have an extended distribution, which provides a good fit to the electron recoil energy spectrum. We estimated the flux of $ψ$ from dark matter annihilations in the galaxy and further determined th…
