We present a novel unifying interpretation of excess event rates observed in several dark matter direct-detection experiments that utilize single-electron threshold semiconductor detectors. Despite their different locations, exposures, readout techniques, detector composition, and operating depths, these experiments all observe statistically significant excess event rates of $\sim$ 10 Hz/kg. However, none of these persistent excesses has yet been reported as a dark matter signal because individually, each can be attributed to different well-motivated but unmodeled backgrounds, and taken together, they cannot be explained by dark matter particles scattering elastically off detector nuclei or electrons. We show that these results can be reconciled if the semiconductor detectors are seeing a collective inelastic process, consistent with exciting a plasmon. We further show that plasmon excitation could arise in two compelling dark matter scenarios, both of which can explain rates of existing signal excesses in germanium and, at least at the order of magnitude level, across several single-electron threshold detectors. At least one of these scenarios also yields the correct relic density from thermal freeze-out. Both dark matter scenarios motivate a radical rethinking of the standard interpretations of dark matter-electron scattering from recent experiments.
In their recent preprint [arXiv:2002.06937], Kurinsky, Baxter, Kahn, and Krnjaic assume an unphysical ionization yield for plasmon excitations in order to claim a possible dark matter signal. Their proposed signal is not possible based on known physics, but their proposed detection method warrants further investigation.
Dark and baryonic matter contribute comparable energy density to the present Universe. The dark matter may also be responsible for the cosmic positron/electron excesses. We connect these phenomena with Dirac seesaw for neutrino masses. In our model (i) the dark matter relic density is a dark matter asymmetry generated simultaneously with the baryon asymmetry so that we can naturally understand the coincidence between the dark and baryonic matter; (ii) the dark matter mostly decays into the leptons so that its decay can interpret the anomalous cosmic rays with positron/electron excesses.
Recently data from PAMELA, ATIC, FERMI-LAT and HESS show that there are $e^{\pm}$ excesses in the cosmic ray energy spectrum. PAMELA observed excesses only in $e^+$, but not in anti-proton spectrum. ATIC, FERMI-LAT and HESS observed excesses in $e^++e^-$ spectrum, but the detailed shapes are different which requires future experimental observations to pin down the correct data set. Nevertheless a lot of efforts have been made to explain the observed $e^\pm$ excesses, and also why PAMELA only observed excesses in $e^+$ but not in anti-proton. In this brief review we discuss one of the most popu…
Dark matter with Sommerfeld-enhanced annihilation has been proposed to explain observed cosmic ray positron excesses in the 10 GeV to TeV energy range. We show that the required enhancement implies thermal relic densities that are too small to be all of dark matter. We also show that the dark matter is sufficiently self-interacting that observations of elliptical galactic dark matter halos exclude large Sommerfeld enhancement for light force carriers. Resonant Sommerfeld enhancement does not modify these conclusions, and the astrophysical boosts required to resolve these discrepancies are disf…
We explore the possibility that the recently reported diphoton excess at ATLAS and CMS can be accommodated within a minimal extension of a left-right symmetric model. Our setup is able to simultaneously explain the Run 2 diphoton and Run 1 diboson excesses, while providing a standard thermal freeze-out of weak-scale dark matter. In this scenario, the 750 GeV neutral right-handed Higgs triplet is responsible for the diphoton excess. Interactions of this state with the neutral and charged components of dark matter multiplets provide the dominant mechanisms for production and decay. A striking si…
We study a scenario that a hidden gaugino dark matter decays into the standard-model particles (and their supersymmetric partners) through a kinetic mixing with the gaugino of a U(1)B-L broken at a scale close to the grand unification scale. We show that decay of the hidden gaugino can explain excesses in the cosmic-ray electrons and positrons observed by PAMELA and Fermi.
We show that Q-ball decay in Affleck-Dine baryogenesis models can account for dark matter when the annihilation cross-section is sufficiently enhanced to explain the positron and electron excesses observed by PAMELA, ATIC and PPB-BETS. For Affleck-Dine baryogenesis along a d = 6 flat direction, the reheating temperature is approximately 30 GeV and the Q-ball decay temperature is in the range 10-100 MeV. The LSPs produced by Q-ball decay annihilate down to the observed dark matter density if the cross-section is enhanced by a factor ~ 10^3 relative to the thermal relic cross-section.
Intriguing signals with excesses over expected backgrounds have been observed in many astrophysical and terrestrial settings, which could potentially have a dark matter origin. Astrophysical excesses include the Galactic Center GeV gamma-ray excess detected by the Fermi Gamma-Ray Space Telescope, the AMS antiproton and positron excesses, and the 511 and 3.5 keV X-ray lines. Direct detection excesses include the DAMA/LIBRA annual modulation signal, the XENON1T excess, and low-threshold excesses in solid state detectors. We discuss avenues to resolve these excesses, with actions the field can ta…
We perform a detailed study of scalar dark matter with triplet Higgs extensions of the Standard Model in order to explain the cosmic ray electron and positron excesses reported by AMS-02 and DAMPE. A detailed analysis of AMS-02 positron excess reveals that for different orderings (normal, inverted and quasi-degenerate) of neutrino mass, the hybrid triplet Higgs portal framework is more favored with respect to the single triplet Higgs portal for TeV scale dark matter. We also show that the resonant peak and continuous excess in DAMPE cosmic ray data can be well explained with the hybrid triplet…
PAMELA and ATIC recently reported excesses in e+ e- cosmic rays. Since the interpretation in terms of DM annihilations was found to be not easily compatible with constraints from photon observations, we consider the DM decay hypothesis and find that it can explain the e+ e- excesses compatibly with all constraints, and can be tested by dedicated HESS observations of the Galactic Ridge. ATIC data indicate a DM mass of about 2 TeV: this mass naturally implies the observed DM abundance relative to ordinary matter if DM is a quasi-stable composite particle with a baryon-like matter asymmetry. Tech…
Recent results from experiments like PAMELA have pointed to excesses of e+e- in cosmic rays. If interpreted in terms of Dark Matter annihilations, they imply the existence of an abundant population of e+e- in the galactic halo at large. We consider the high energy gamma ray fluxes produced by Inverse Compton scattering of interstellar photons on such e+e-, and compare them with the available data from EGRET and some preliminary data from FERMI. We consider different observation regions of the sky and a range of DM masses, annihilation channels and DM profiles. We find that large portions of th…
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 investigate diboson signals in the Standard Model (SM) with an extended Higgs sector, motivated by the excesses in the diboson channels at the LHC. We begin with the unitarity sum-rules of the weak gauge boson scattering assuming the Higgs sector is extended. According to the sum-rules, we discuss the Higgs interpretations of the diboson signals and the consistency with the ATLAS diboson anomaly and other experimental constraints. As a concrete example, we propose a two-Higgs-doublet model where the Yukawa coupling of an extra CP-even scalar with up-type quark is relatively large. The dibos…
In hidden sector models, dark matter does not directly couple to the particle content of the Standard Model, strongly suppressing rates at direct detection experiments, while still allowing for large signals from annihilation. In this paper, we conduct an extensive study of hidden sector dark matter, covering a wide range of dark matter spins, mediator spins, interaction diagrams, and annihilation final states, in each case determining whether the annihilations are s-wave (thus enabling efficient annihilation in the universe today). We then go on to consider a variety of portal interactions th…
We investigate models involving a vector-like quark X, which forms a 750 GeV bound state and reproduces the observed diphoton signals at the LHC, in connection with other excesses in the LHC data. An exotic hypercharge of -4/3 is required to fit the signal cross section, which indicates that there is additional particle(s) that mediates the decay of X in the full theory. We find that, introducing an SU(2) doublet vector-like quark of mass around 600 GeV in our UV-complete framework can accommodate not only the diphoton but also the on-Z excess (and potentially a slight excess in the monojet ev…
In this letter, we suggest that a nearby clump of 600-1000 GeV neutralinos may be responsible for the excesses recently observed in the cosmic ray positron and electron spectra by the PAMELA and ATIC experiments. Although neutralino dark matter annihilating throughout the halo of the Milky Way is predicted to produce a softer spectrum than is observed, and violate constraints from cosmic ray antiproton measurements, a large nearby (within 1-2 kiloparsecs of the Solar System) clump of annihilating neutralinos can lead to a spectrum which is consistent with PAMELA and ATIC, while also producing …
We show that R-parity violating decay of Wino dark matter of mass \sim 3 TeV can naturally account for the flux and spectral shape of the cosmic-ray electrons and positrons observed by the PAMELA and Fermi satellites. To provide a theoretical basis for the scenario, we also present a model that trilinear R-parity breaking appears with a coefficient suppressed by powers of the gravitino mass, which naturally leads to the Wino lifetime of O(10^26) sec.
In interacting multi-component dark matter (DM) models, if the DM components are nearly degenerate in mass and the interactions between them are strong enough, the relatively heavy DM components can be converted into lighter ones at late time after the thermal decoupling. Consequently, the relic density of the lightest DM component can be considerably enhanced at late time. This may contribute to an alternative source of boost factor required to explain the positron and electron excesses reported by the recent DM indirect search experiments such as PAMELA, Fermi-LAT and HESS etc..
The precise measurements of energy spectra of cosmic ray positrons and/or electrons by recent experiments show clear excesses above 10 GeV. Moreover, a potential sharp spectral feature was suggested by the Dark Matter Particle Explorer (DAMPE) data. These results inspire quite a number of discussions on the connection with either the annihilation/decay of dark matter (DM) or the astrophysical origins. Here we discuss a DM scenario in which DM particles could annihilate and decay into standard model particle pairs simultaneously. In this model, the peak structure is due to the DM annihilation i…
Recently reported diboson and diphoton excesses at LHC are interpreted to be connected with heavy $WW$ zero spin resonances. The resonances appears due to the wouldbe anomalous triple interaction of the weak bosons, which is defined by well-known coupling constant $λ$. The $2\, TeV$ anomaly tentatively corresponds to weak isotopic spin 2 scalar state and the $γγ\,\,750\, GeV$ anomaly corresponds to weak isotopic spin 0 pseudoscalar state. We obtain estimates for the effect, which qualitatively agree with ATLAS data. Effects are predicted in a production of $W^+ W^-, (Z,γ) (Z,γ)$ via resonance …
In models of dark matter (DM) with Sommerfeld-enhanced annihilation, where the annihilation rate scales as the inverse velocity, N-body simulations of DM structure formation suggest that the local annihilation signal may be dominated by small, dense, cold subhalos. This contrasts with the usual assumption of a signal originating from the smooth DM halo, with much higher velocity dispersion. Accounting for local substructure modifies the parameter space for which Sommerfeld-enhanced annihilating DM can explain the PAMELA and Fermi excesses. Limits from the inner galaxy and the cosmic microwave …
Dark matter annihilation is one of the leading explanations for the recently observed $e^\pm$ excesses in cosmic rays by PAMELA, ATIC, FERMI-LAT and HESS. Any dark matter annihilation model proposed to explain these data must also explain the fact that PAMELA data show excesses only in $e^\pm$ spectrum but not in anti-proton. It is interesting to ask whether the annihilation mode into anti-proton is completely disallowed or only suppressed at low energies. Most models proposed have negligible anti-protons in all energy ranges. We show that the leptocentric $U(1)_{B-3L_i}$ dark matter model can…
We propose a novel mechanism to explain the positron excesses, which are observed by satellite-based telescopes including PAMELA and AMS-02, in dark matter (DM) scenarios. The novelty behind the proposal is that it makes direct use of DM around the Galactic Center where DM populates most densely, allowing us to avoid tensions from cosmological and astrophysical measurements. The key ingredients of this mechanism include DM annihilation into unstable states with a very long laboratory-frame life time and their "retarded" decay near the Earth to electron-positron pair(s) possibly with other (in)…
We explain the excess of the antiproton fraction recently reported by the AMS-02 experiment by considering collisions between cosmic-ray protons accelerated by a local supernova remnant (SNR) and the surrounding dense cloud. The same "$pp$-collisions" provide the right ratio of daughter particles to fit the observed positron excess simultaneously in the natural model parameters. The supernova happened in relatively lower metalicity than the major cosmic-ray sources. The cutoff energy of electrons marks the supernova age of $\sim 10^{5}$ years, while the antiproton excess may extend to higher e…
We construct a new realization of type-II seesaw for neutrino masses and baryon asymmetry by extending the standard model with one light and two heavy singlet scalars besides one Higgs triplet. The heavy singlets pick up small vacuum expectation values to give a suppressed trilinear coupling between the triplet and doublet Higgs bosons after the light singlet drives the spontaneous breaking of lepton number. The Higgs triplet can thus remain light and be accessible at the LHC. The lepton number conserving decays of the heavy singlets can generate a lepton asymmetry stored in the Higgs triplet …
The cosmic-ray excess observed by PAMELA in the positron fraction and by FERMI and HESS in the electron + positron flux can be interpreted in terms of DM annihilations or decays into leptonic final states. Final states into tau's or 4mu give the best fit to the excess. However, in the annihilation scenario, they are incompatible with photon and neutrino constraints, unless DM has a quasi-constant density profile. Final states involving electrons are less constrained but poorly fit the excess, unless hidden sector radiation makes their energy spectrum smoother, allowing a fit to all the data wi…
We use multi-component decaying dark matter (DM) scenario to explain the possible cosmic ray excesses in the positron fraction recently confirmed by AMS-02 and the total $e^+ +e^-$ flux observed by Fermi-LAT. In the two-component DM models, we find an interesting variation of the flavor structure along with the cutoff of the heavy DM. For the three-component DM case, we focus on a particular parameter range in which the best fits prefer to open only 2 DM decay channels with a third DM contributing nothing to the electron and positron spectra. We show that all models give the reasonable fits to…
The presence of an excess gamma-ray signal toward the Galactic center (GC) has now been well established, and is known as the GC excess. Leading explanations for the signal include mis-modeling of the Galactic diffuse emission along the line of sight, an unresolved population of millisecond pulsars, and/or the annihilation of dark matter (DM). Recently, evidence for another excess gamma-ray signal has been reported toward the outer halo of M31. In this work we interpret the excess signals from both the GC and outer halo of M31 in the framework of DM annihilation, and show that the two spectra …
The data collected by ATIC, PPB-BETS, FERMI-LAT and HESS all indicate that there is an electron/positron excess in the cosmic ray energy spectrum above $\sim$ 100 GeV, although different instrumental teams do not agree on the detailed spectral shape. PAMELA also reported a clear excess feature of the positron fraction above several GeV, but no excess in anti-protons. Here we review the observational status and theoretical models of this interesting observational feature. We pay special attention to various physical interpretations proposed in the literature, including modified supernova remnan…
Based on an $SU(2) \times SU(2) \times U(1)$ effective theory framework (aka $G221$ models), we investigate a leptophobic $SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ model, in which the right-handed $W^\prime$ boson has the mass of around 2 TeV, and predominantly couples to the standard model quarks and the gauge-Higgs sector. This model could explain the resonant excesses near 2 TeV reported by the ATLAS collaboration in the $WZ$ production decaying into hadronic final states, and by the CMS collaboration in the $Wh$ channel decaying into $b\bar{b}\ellν$ and dijet final state. After imposing t…
The new measurement of the $W$ boson mass performed by the CDF experiment at the Tevatron shows a significant deviation not only with the expectation in the Standard Model but also with other precision measurements performed at LEP, the Tevatron and the LHC. We nevertheless take this new measurement at face value and interpret it as an effect of new physics. We particularly try to link it with other possible anomalies such as the recent muon $g-2$ and consider a scenario that addresses some shortcomings of the Standard Model. We show that a model with two doublets and a light pseudoscalar Higg…
Interpretation of LHC excesses at 95 GeV and 152 GeV in an extended Georgi-Machacek model
University of Wisconsin-Madison（威斯康星大学麦迪逊分校）；National Taiwan University（台湾大学）；National Center for Theoretical Sciences（国家理论科学中心）；Instituto de Física Teórica UAM-CSIC（UAM-CSIC理论物理研究所）；Deutsches Elektronen-Synchrotron DESY（德国电子同步加速器）；Universität Hamburg（汉堡大学）
By combining the recent data from AMS-02 with those from Fermi-LAT, we show the emergence of a charge asymmetry in the electron and positron cosmic-ray excesses, slightly favoring the electron component. Astrophysical and dark matter inspired models introduced to explain the observed excesses can be classified according to their prediction for the charge asymmetry and its energy dependence. Future data confirming the presence of a charge asymmetry, would imply that an asymmetric production mechanism is at play.
The recently introduced cosmic sum rules combine the data from PAMELA and Fermi-LAT cosmic ray experiments in a way that permits to neatly investigate whether the experimentally observed lepton excesses violate charge symmetry. One can in a simple way determine universal properties of the unknown component of the cosmic rays. Here we attribute a potential charge asymmetry to the dark sector. In particular we provide models of asymmetric dark matter able to produce charge asymmetric cosmic rays. We consider spin zero, spin one and spin one-half decaying dark matter candidates. We show that lept…
Recently the ATIC and PAMELA collaborations released their results which show the abundant e^\pm excess in cosmic rays well above the background, but not for the \bar{p}. Their data if interpreted as the dark matter particles' annihilation imply that the new physics with the dark matter is closely related to the lepton sector. In this paper we study the possible connection of the new physics responsible for the cosmic e^\pm excesses to the neutrino mass generation. We consider a class of models and do the detailed numerical calculations. We find that these models can natually account for the A…
We construct a Dark Matter (DM) annihilation module that can encompass the predictions from a wide array of models built to explain the recently reported PAMELA and ATIC/PPB-BETS excesses. We present a detailed analysis of the injection spectrums for DM annihilation and quantitatively demonstrate effects that have previously not been included from the particle physics perspective. With this module we demonstrate the parameter space that can account for the aforementioned excesses and be compatible with existing high energy gamma ray and neutrino experiments. However, we find that it is relativ…
In this paper we propose a dark matter model and study aspects of its phenomenology. Our model is based on a new dark matter sector with a U(1)' gauge symmetry plus a discrete symmetry added to the Standard Model of particle physics. The new fields of the dark matter sector have no hadronic charges and couple only to leptons. Our model can not only give rise to the observed neutrino mass hierarchy, but can also generate the baryon number asymmetry via non-thermal leptogenesis. The breaking of the new U(1)' symmetry produces cosmic strings. The dark matter particles are produced non-thermally f…
Anomalies in direct and indirect detection have motivated models of dark matter consisting of a multiplet of nearly-degenerate states, coupled by a new GeV-scale interaction. We perform a careful analysis of the thermal freezeout of dark matter annihilation in such a scenario. We compute the range of "boost factors" arising from Sommerfeld enhancement in the local halo for models which produce the correct relic density, and show the effect of including constraints on the saturated enhancement from the cosmic microwave background (CMB). We find that boost factors from Sommerfeld enhancement of …
Since the discovery in 2012 of the Higgs boson at the LHC, as the last missing piece of the Standard Model of particle physics, any hint of new physics has been intensively searched for, with no confirmation to date. There are however slight deviations from the SM that are worth investigating. The CMS collaboration has reported, in a search for heavy resonances decaying in $t \bar t$ with a 13-TeV center-of-mass energy and a luminosity of 35.9 fb$^{-1}$, deviations from the SM predictions at the 3.5$σ$ level locally (1.9$σ$ after the look-elsewhere effect). In addition, in the ditau final stat…
Recent measurements by the ARCADE2 experiment unambiguously show an excess in the isotropic radio background at frequencies below the GHz scale. We argue that this excess may be a natural consequence of the interaction of visible and dark matter in the early universe if the dark matter consists of heavy nuggets of quark matter. Explanation of the observed radio band excess requires the introduction of no new parameters, rather we exploit the same dark matter model and identical normalization parameters to those previously used to explain other excesses of diffuse emission from the centre of ou…
Recently PAMELA collaboration published the cosmic nuclei and electron spectra with high precision, together with the cosmic antiproton data updated, and the Fermi-LAT collaboration also updated the measurement of the total $e^+e^-$ spectrum to lower energies. In this paper we develop a Markov Chain Monte Carlo (MCMC) package {\it CosRayMC}, based on the GALPROP cosmic ray propagation model to study the implications of these new data. It is found that if only the background electrons and secondary positrons are considered, the fit is very bad with $χ_{\rm red}^2 \approx 3.68$. Taking into acco…
We point out that the gamma-ray excesses in the galactic center and in the dwarf galaxy Reticulum II can both be well explained within the simplest dark matter model. We find that the corresponding region of parameter space will be tested by direct and indirect dark matter searches in the near future.
The ATLAS collaboration has reported excesses in searches for resonant diboson production decaying into hadronic final states. This deviation from the Standard Model prediction may be a signature of an extra bosonic particle having a mass of around 2 TeV with a fairly narrow width, which implies the presence of a new perturbative theory at the TeV scale. In this paper, we study interpretations of the signal and its implication to physics beyond the Standard Model. We find that the resonance could be regarded as a leptophobic vector particle, which could explain a part of the observed excesses …
It has been long discussed that cosmic rays may contain signals of dark matter. In the last couple of years an anomaly of cosmic-ray positrons has drawn a lot of attentions, and recently an excess in cosmic-ray anti-proton has been reported by AMS-02 collaboration. Both excesses may indicate towards decaying or annihilating dark matter with a mass of around 1-10 TeV. In this article we study the gamma rays from dark matter and constraints from cross correlations with distribution of galaxies, particularly in a local volume. We find that gamma rays due to inverse-Compton process have large inte…
Recent cosmic ray, gamma ray, and microwave signals observed by Fermi, PAMELA, and WMAP indicate an unexpected primary source of e+e- at 10-1000 GeV. We fit these data to "standard backgrounds" plus a new source, assumed to be a separable function of position and energy. For the spatial part, we consider three cases: annihilating dark matter, decaying dark matter, and pulsars. In each case, we use GALPROP to inject energy in log-spaced energy bins and compute the expected cosmic-ray and photon signals for each bin. We then fit a linear combination of energy bins, plus backgrounds, to the data.…
Motivated by the recently reported diboson and dijet excesses in Run 1 data at ATLAS and CMS, we explore models of mixed dark matter in left-right symmetric theories. In this study, we calculate the relic abundance and the elastic scattering cross section with nuclei for a number of dark matter candidates that appear within the fermionic multiplets of left-right symmetric models. In contrast to the case of pure multiplets, WIMP-nucleon scattering proceeds at tree-level, and hence the projected reach of future direct detection experiments such as LUX-ZEPLIN and XENON1T will cover large regions …
A puzzling excess in gamma-rays at GeV energies has been observed in the center of our galaxy using Fermi-LAT data. Its origin is still unknown, but it is well fitted by Weakly Interacting Massive Particles (WIMPs) annihilations into quarks with a cross section around $10^{-26}{\rm cm^3 s^{-1}}$ with masses of $20-50$~GeV, scenario which is promptly revisited. An excess favoring similar WIMP properties has also been seen in anti-protons with AMS-02 data potentially coming from the Galactic Center as well. In this work, we explore the possibility of fitting these excesses in terms of semi-annih…
We provide conservative bounds on the dark matter cross-section and lifetime from final state radiation produced by annihilation or decay into charged leptons, either directly or via an intermediate particle $ϕ$. Our analysis utilizes the experimental gamma-ray flux upper limits from four Milky Way dwarf satellites: HESS observations of Sagittarius and VERITAS observations of Draco, Ursa Minor, and Willman 1. Using 90% confidence level lower limits on the integrals over the dark matter distributions, we find that these constraints are largely unable to rule out dark matter annihilations or dec…
This note is an attempt to interpret some excesses, not yet significant due to systematics, observed by ATLAS and CMS in various analyses related to the standard channels ttH, ttZ and ttW. It is argued, within a composite interpretation of top particles, that such excesses are not necessarily related to these channels themselves, although this is not excluded, but due to the underlying presence of either vector-like heavy quarks tprime,bprime or to final states as predicted in composite theories. The outcome of this discussion is that although it will not be easy to reach an exclusive interpre…
