We show that a couplet, a pair of closely spaced photon lines, in the X-ray spectrum is a distinctive feature of lepton flavored dark matter models for which the mass spectrum is dictated by Minimal Flavor Violation. In such a scenario, mass splittings between different dark matter flavors are determined by Standard Model Yukawa couplings and can naturally be small, allowing all three flavors to be long-lived and contribute to the observed abundance. Then, in the presence of a tiny source of flavor violation, heavier dark matter flavors can decay via a dipole transition on cosmological timescales, giving rise to three photon lines. The ratios of the line energies are completely determined in terms of the charged lepton masses, and constitute a firm prediction of this framework. For dark matter masses of order the weak scale, the couplet lies in the keV-MeV region, with a much weaker line in the eV-keV region. This scenario constitutes a potential explanation for the recent claim of the observation of a 3.5 keV line. The next generation of X-ray telescopes may have the necessary resolution to resolve the double line structure of such a couplet.
The current status of flavored dark matter is reviewed. We discuss the main experimental constraints on models of flavored dark matter and survey some possible considerations which are relevant for the constructions of models. We then review the application of existing flavor principles to dark matter, with an emphasis on minimal flavor violation, and discuss implications of flavored dark matter on collider phenomenology.
Minimal Flavor Violation offers an alternative symmetry rationale to R-parity conservation for the suppression of proton decay in supersymmetric extensions of the Standard Model. The naturalness of such theories is generically under less tension from LHC searches than R-parity conserving models. The flavor symmetry can also guarantee the stability of dark matter if it carries flavor quantum numbers. We outline general features of supersymmetric flavored dark matter (SFDM) models within the framework of MFV SUSY. A simple model of top flavored dark matter is presented. If the dark matter is a t…
In this paper we investigate the phenomenology of the electron flavored Dirac dark matter with two types of portal interactions. We analyze constraints from the electron magnetic moment anomaly, LHC searches of singly charged scalar, dark matter relic abundance as well as direct and indirect detections. Our study shows that the available parameter space is quite constrained, but there are parameter space that is compatible with the current data. We further show that the DAMPE cosmic ray electron excess, which indicates cosmic ray excess at around 1.5 TeV, can be interpreted as the annihilation…
We study a renormalizable scalar singlet dark matter model based on $Z_4$ lepton flavor symmetry. A $μτ$-philic scalar doublet is introduced to explain the discrepancy between the experimental value and the theoretical prediction of the muon anomalous magnetic moment. At the same time, these flavored scalars play the role of a mediator which connects dark matter and standard model particles. The observed relic abundance of the dark matter is easily maintained while satisfying the current severe constraints on the dark matter from various experiments and observations thanks to the flavor off-di…
The DAMPE experiment has recently reported strong indications for the existence of an excess of high-energy electrons and positrons. If interpreted in terms of the annihilation of dark matter, the DAMPE result restricts the dark matter mass and possible annihilation channels to a few case. In this paper we explain the DAMPE result with the electron-flavored $Z^\prime$-portal fermionic dark matter. We show that the Dirac dark matter scenario is promising to explain the excess via the process $\bar χχ\to\mathbf{Z}'\to \bar e e$. The reduced annihilation cross section is limited in a range of $10…
We consider the effective field theory generated by a heavy mediator that connects Standard Model particles to a Dark Sector, considering explicitly the flavor structure of the operators. In particular, we study the model independent running and mixing between operators, as well as their matching at the electroweak scale. In addition to the explicit expression of the Renormalization Group Equations, we show the numerical solutions as well as some approximate analytical expressions that help understanding these solutions. At low energy, our results are particularly important in the case of ligh…
In this paper we consider loop corrections to the spin-independent WIMP-nucleon scattering cross section in bottom-quark flavored scalar-type dark matter models. We focus on two scenarios: (a) a complex scalar dark matter with a scalar particle as the mediator; and (b) a real scalar dark matter with a vector boson as the mediator. In both scenarios, the direct detection cross sections are either spin-dependent or kinematically forbidden at the tree-level. Corrections induced by the WIMP-gluon effective operator, scalar-type WIMP-quark effective operator, and the twist-2 effective operator are …
In this paper we preform a systematic study of the tau flavored dark matter model by introducing two kinds of mediators (a scalar doublet and a charged scalar singlet). The electromagnetic properties of the dark matter, as well as their implications in dark matter direct detections, are analyzed in detail. The model turns out contributing a significant radiative correction to the tau lepton mass, in addition to loosing the tension between the measured dark matter relic density and constraints of dark matter direct detections. The loop corrections can be ${\cal O}(10\%)$ of the total tau mass. …
We propose a simple model where dark matter (DM) carries top flavor and couples to the Standard Model through the top quark within a framework of minimal flavor violation (MFV). Top-flavored DM can explain the anomalous top forward-backward asymmetry observed at the Tevatron, while remaining consistent with other top observables at colliders. By virtue of its large coupling to top, DM acquires a sizable loop coupling to the Z boson, and the relic density is set by annihilation through the Z. We also discuss contraints from current direct detection searches, emphasizing the role of spin-depende…
We consider the possibility that dark matter can communicate with the Standard Model fields via flavor interactions. We take the dark matter to belong to a "dark sector" which contains at least two types, or "flavors", of particles and then hypothesize that the Standard Model fields and dark matter share a common interaction which depends on flavor. As, generically, interaction eigenstates and mass eigenstates need not coincide, we consider both flavor-changing and flavor-conserving interactions. These interactions are then constrained by meson decays, kaon mixing, and current collider bounds,…
We study the interplay of flavor and dark matter phenomenology for models of flavored dark matter interacting with quarks. We allow an arbitrary flavor structure in the coupling of dark matter with quarks. This coupling is assumed to be the only new source of violation of the Standard Model flavor symmetry extended by a $U(3)_χ$ associated with the dark matter. We call this ansatz Dark Minimal Flavor Violation (DMFV) and highlight its various implications, including an unbroken discrete symmetry that can stabilize the dark matter. As an illustration we study a Dirac fermionic dark matter $χ$ w…
We explore a novel flavor structure in the interactions of dark matter with the Standard Model. We consider theories in which both the dark matter candidate, and the particles that mediate its interactions with the Standard Model fields, carry flavor quantum numbers. The interactions are skewed in flavor space, so that a dark matter particle does not directly couple to the Standard Model matter fields of the same flavor, but only to the other two flavors. This framework respects Minimal Flavor Violation, and is therefore naturally consistent with flavor constraints. We study the phenomenology …
Phenomenological studies of Flavored Dark Matter (FDM) models often have to assume a near-diagonal flavor structure in the coupling matrix in order to remain consistent with bounds from flavor violating processes. In this paper we show that for Lepton FDM, such a structure can naturally arise from an extra dimensional setup. The extra dimension is taken to be flat, with the dark matter and mediator fields confined to a brane on one end of the extra dimension, and the Higgs field to a brane on the other end. The Standard Model fermion and gauge fields are the zero modes of corresponding bulk fi…
In this work, we address two paradoxes. The first is that the measured dark-matter relic density can be satisfied with new physics at O(100 GeV - 1 TeV), while the null results from direct-detection experiments place lower bounds of O(10 TeV) on a new-physics scale. The second puzzle is that the severe suppression of lepton-flavor-violating processes involving electrons, e.g. mu->3e, tau->e mu mu, etc., implies that generic new-physics contributions to lepton interactions cannot exist below O(10 - 100 TeV), whereas the 3.6sigma deviation of the muon g-2 from the standard model can be explained…
In flavored dark matter models, dark matter can scatter off of nuclei through Higgs and photon exchange, both of which can arise from renormalizable interactions and individually lead to strong constraints from direct detection. While these two interaction channels can destructively interfere in the scattering amplitude, for a thermal relic with equal abundances for the dark matter particle and its antiparticle, this produces no effect on the total event rate. Focusing on lepton-flavored dark matter, we show that it is quite natural for dark matter to have become asymmetric during high-scale l…
Thermal relic dark matter particles with a mass of 31-40 GeV and that dominantly annihilate to bottom quarks have been shown to provide an excellent description of the excess gamma rays observed from the center of the Milky Way. Flavored dark matter provides a well-motivated framework in which the dark matter can dominantly couple to bottom quarks in a flavor-safe manner. We propose a phenomenologically viable model of bottom flavored dark matter that can account for the spectral shape and normalization of the gamma-ray excess while naturally suppressing the elastic scattering cross sections p…
We consider theories where the dark matter particle carries flavor quantum numbers, and has renormalizable contact interactions with the Standard Model fields. The phenomenology of this scenario depends sensitively on whether dark matter carries lepton flavor, quark flavor or its own internal flavor quantum numbers. We show that each of these possibilities is associated with a characteristic type of vertex, has different implications for direct detection experiments and gives rise to distinct collider signatures. We find that the region of parameter space where dark matter has the right abunda…
We investigate the phenomenology of flavored dark matter (DM). DM stability is guaranteed by an accidental ${\mathcal Z}_3$ symmetry, a subgroup of the standard model (SM) flavor group that is not broken by the SM Yukawa interactions. We consider an explicit realization where the quark part of the SM flavor group is fully gauged. If the dominant interactions between DM and visible sector are through flavor gauge bosons, as we show for Dirac fermion flavored DM, then the DM mass is bounded between roughly $0.5$ TeV and $5$ TeV if the DM multiplet mass is split only radiatively. In general, howe…
It is an intriguing possibility that dark matter (DM) could have flavor quantum numbers like the quarks. We propose and investigate a class of UV-complete models of this kind, in which the dark matter is in a scalar triplet of an SU(3) flavor symmetry, and interacts with quarks via a colored flavor-singlet fermionic mediator. Such mediators could be discovered at the LHC if their masses are $\sim 1$ TeV. We constrain the DM-mediator couplings using relic abundance, direct detection, and flavor-changing neutral-current considerations. We find that, for reasonable values of its couplings, scalar…
Proto-neutron stars forming a few seconds after core-collapse supernovae are hot and dense environments where hyperons can be efficiently produced by weak processes. By making use of various state-of-the-art supernova simulations combined with the proper extensions of the equations of state including $Λ$ hyperons, we calculate the cooling of the star induced by the emission of dark bosons $X^0$ through the decay $Λ\to n X^0$. Comparing this novel energy-loss process to the neutrino cooling of SN 1987A allows us to set stringent constraints on massless dark photons and axions with flavor-violat…
We consider a class of flavored dark matter (DM) theories where dark matter interacts with the Standard Model lepton fields at the renormalizable level. We allow for a general coupling matrix between the dark matter and leptons whose structure is beyond the one permitted by the minimal flavor violation (MFV) assumption. It is assumed that this is the only new source of flavor violation in addition to the Standard Model (SM) Yukawa interactions. The setup can be described by augmenting the SM flavor symmetry by an additional $\mathrm{SU}(3)_χ$, under which the dark matter $χ$ transforms. This f…
Proto-neutron stars forming a few seconds after core-collapse supernovae are hot and dense environments where hyperons can be efficiently produced by weak processes. By making use of various state-of-the-art supernova simulations combined with the proper extensions of the equations of state including $Λ$ hyperons, we calculate the cooling of the star induced by the emission of dark particles $X^0$ through the decay $Λ\to n X^0$. Comparing this novel energy-loss process to the neutrino cooling of SN 1987A allows us to set a stringent upper limit on the branching fraction, BR$(Λ\to n X^0)\leq 8\…
In the standard model (SM), lepton flavor violating (LFV) Higgs decay is absent at renormalizable level and thus it is a good probe to new physics. In this article we study a type of new physics that could lead to large LFV Higgs decay, i.e., a lepton-flavored dark matter (DM) model which is specified by a Majorana DM and scalar lepton mediators. Different from other similar models with similar setup, we introduce both left-handed and right-handed scalar leptons. They allow large LFV Higgs decay and thus may explain the tentative Br$(h\raτμ)\sim1\%$ experimental results from the LHC. In partic…
We study the experimental signatures of top flavored dark matter (top FDM) in direct detection searches and at the LHC. We show that for a dark matter mass above 200 GeV, top FDM can be consistent with current bounds from direct detection experiments and relic abundance constraints. We also show that next generation direct detection experiments will be able to exclude the entire perturbative parameter region for top FDM. For regions of parameter space where the flavor partners of top FDM are not readily produced, the LHC signatures of top FDM are similar to those of other models previously stu…
In both scotogenic neutrino and flavor dark matter models, the dark sector communicates with the standard model fermions via Yukawa portal couplings. We propose an economic scenario that scotogenic neutrino and flavored mediator share the same inert Higgs doublet and all are charged under a hidden gauged $U(1)$ symmetry. The dark Z2 symmetry in dark sector is regarded as the remnant of this hidden $U(1)$ symmetry breaking. In particular, we investigate a dark $U(1)_D$ (and also a $U(1)_{B-L}$) model which unifies scotogenic neutrino and top-flavored mediator. In this model dark tops and dark n…
We explore scalar dark matter that is part of a lepton flavor triplet satisfying symmetry requirements under the hypothesis of minimal flavor violation. Beyond the standard model, the theory contains in addition three right-handed neutrinos that participate in the seesaw mechanism for light neutrino mass generation. The dark-matter candidate couples to standard-model particles via Higgs-portal renormalizable interactions as well as to leptons through dimension-six operators, all of which have minimal flavor violation built-in. We consider restrictions on the new scalars from the Higgs boson me…
In this work, we study the thermodynamic behavior of heavy-flavored meson matter in the framework of $(σ,ω)$-meson-exchange model in relativistic mean field theory. We find a decreasing of the effective masses of $D$ and $B$ mesons as the temperature increases. By using the effective mass and maximum value of dissociation temperatures available from lattice QCD, the masses of the bound states $D \bar{D}$ and $B \bar{B}$ are estimated in 2 MeV for both molecules. For the $B$-meson matter, the pressure presents an exotic behavior, being negative for temperatures above 6.6 times the deconfinement…
We study a mechanism where the dark matter number density today arises from asymmetries generated in the dark sector in the early universe, even though total dark matter number remains zero throughout the history of the universe. The dark matter population today can be completely symmetric, with annihilation rates above those expected from thermal WIMPs. We give a simple example of this mechanism using a benchmark model of flavored dark matter. We discuss the experimental signatures of this setup, which arise mainly from the sector that annihilates the symmetric component of dark matter.
Dark Matter emission at Belle II and NA62 in Minimal Flavor Violation framework
Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati（意大利国家核物理研究所，弗朗卡蒂国家实验室）；Asia Pacific Center for Theoretical Physics（亚太理论物理中心）；Department of Physics, Pohang University of Science and Technology（浦项科技大学物理系）；Department of Physics, Kyushu University（九州大学物理系）；CERN, European Organization for Nuclear Research（欧洲核子研究组织（CERN））；LAPTh, Université Savoie Mont-Blanc et CNRS（萨瓦蒙布朗大学与法国国家科学研究中心联合理论物理实验室）
Standard Model extensions with light axions are well-motivated by the observed Dark Matter abundance and the Peccei-Quinn solution to the Strong CP Problem. In general such axions can have large flavor-violating couplings to SM fermions, which naturally arise in scenarios where the Peccei-Quinn symmetry also explains the hierarchical pattern of fermion masses and mixings. I will discuss how these couplings allow for efficient axion production from the decays of SM particles, giving the opportunity to probe flavored axion Dark Matter with precision flavor experiments, astrophysics and cosmology…
We investigate a simple variant of type-II seesaw, responsible for neutrino mass generation, where the particle spectrum is extended with one singlet right-handed neutrino and an inert Higgs doublet, both odd under an additional $Z_2$ symmetry. While the role of the dark matter is played by the lightest neutral component of the inert Higgs doublet, its interaction with the Standard Model lepton doublets and the right-handed neutrino turns out to be crucial in generating the correct baryon abundance of the Universe through flavored leptogenesis from the decay of the $SU(2)_L$ scalar triplet, in…
Dark, chiral fermions carrying lepton flavor quantum numbers are natural candidates for freeze-in. Small couplings with the Standard Model fermions of the order of lepton Yukawas are `automatic' in the limit of Minimal Flavor Violation. In the absence of total lepton number violating interactions, particles with certain representations under the flavor group remain absolutely stable. For masses in the GeV-TeV range, the simplest model with three flavors, leads to signals at future direct detection experiments like DARWIN. Interestingly, freeze-in with a smaller flavor group such as $SU(2)$ is …
In this paper we revisit constraints on the leptophilic dark matter (DM) arising from the DM indirect detection experiments. Interactions between the charged leptons and the scalar-type, Dirac-type or vector-type DM are written in terms of effective operators. After classifying all interactions that may give non-zero signals in indirect detections, we study constraints on the parameter space of these effective interactions from the latest results of AMS-02, Planck, Fermi-LAT and H.E.S.S., as well as the observed relic abundance. Main results are summarized in the Table. I. It shows that the $τ…
We present U(1) flavor models for leptophobic Z' with flavor dependent couplings to the right-handed up-type quarks in the Standard Model, which can accommodate the recent data on the top forward-backward (FB) asymmetry and the dijet resonance associated with a W boson reported by CDF Collaboration. Such flavor-dependent leptophobic charge assignments generally require extra chiral fermions for anomaly cancellation. Also the chiral nature of U(1)' flavor symmetry calls for new U(1)'-charged Higgs doublets in order for the SM fermions to have realistic renormalizable Yukawa couplings. The strin…
We investigate the phenomenology of a dark matter scenario containing two generations of the dark matter particle, differing only by their mass and their couplings to the other particles, akin to the quark and lepton sectors of the Standard Model. For concreteness, we consider the case where the two dark matter generations are Majorana fermions that couple to a right-handed lepton and a scalar mediator through Yukawa couplings. We identify different production regimes in the multi-flavor dark matter scenario and we argue that in some parts of the parameter space the heavier generation can play…
We study a scenario in which the only light new particles are a Majorana fermion dark matter candidate and one or more QCD-charged scalars, which couple to light quarks. This scenario has several interesting phenomenological features if the new particles are nearly degenerate in mass. In particular, LHC searches for the light scalars have reduced sensitivity, since the visible and invisible products tend to be softer. Moreover, dark matter-scalar co-annihilation can allow even relatively heavy dark matter candidates to be consistent thermal relics. Finally, the dark matter nucleon scattering c…
We revisit the discrete dark matter model with $A_4$ flavor symmetry originally introduced by M.Hirsch {\it et.al}. We show that radiative corrections can lead to non-zero $θ_{13}$ and non-zero mass for the lightest neutrino. We find an interesting relation among neutrino mixing parameters and it indicates the sizable deviation of $s_{23}$ from the maximal angle $s_{23}^2=1/2$ and the degenerate mass spectrum for neutrinos. Also we study the possibilities that the right-handed neutrino is a dark matter candidate. Assuming the thermal freeze-out explains observed dark matter abundance, TeV-scal…
We consider theories of flavored dark matter, in which the dark matter particle is part of a multiplet transforming nontrivially under the flavor group of the Standard Model in a manner consistent with the principle of Minimal Flavor Violation (MFV). MFV automatically leads to the stability of the lightest state for a large number of flavor multiplets. If neutral, this particle is an excellent dark matter candidate. Furthermore, MFV implies specific patterns of mass splittings among the flavors of dark matter and governs the structure of the couplings between dark matter and ordinary particles…
Neutralino dark matter in supersymmetric models is revisited in the presence of flavor violation in the soft supersymmetry breaking sector. We focus on flavor violation in the sleptonic sector and study the implications for the co-annihilation regions. Flavor violation is introduced by a single $\tildeμ_R-\tildeτ_R$ insertion in the slepton mass matrix. Limits on this insertion from BR($τ\to μ+ γ$) are weak in some regions of the parameter space where cancellations happen within the amplitudes. We look for overlaps in parameter space where both the co-annihilation condition as well as the canc…
We propose a predictive $Q_4$ flavored 2HDM model, where the scalar sector is enlarged by the inclusion of several gauge singlet scalars and the fermion sector by the inclusion of right handed Majorana neutrinos. In our model, the $Q_4$ family symmetry is supplemented by several auxiliary cyclic symmetries, whose spontaneous breaking produces the observed pattern of SM charged fermion masses and quark mixing angles. The light active neutrino masses are generated from an inverse seesaw mechanism at one loop level thanks to a remnant preserved $Z_2$ symmetry. Our model succesfully reproduces the…
We study the phenomenology of mixed-sneutrino dark matter in the Minimal R-Symmetric Supersymmetric Standard Model (MRSSM). Mixed sneutrinos fit naturally within the MRSSM, as the smallness (or absence) of neutrino Yukawa couplings singles out sneutrino A-terms as the only ones not automatically forbidden by R-symmetry. We perform a study of randomly generated sneutrino mass matrices and find that (i) the measured value of $Ω_{DM}$ is well within the range of typical values obtained for the relic abundance of the lightest sneutrino, (ii) with small lepton-number-violating mass terms $m_{nn}^{2…
We propose a flavored $U(1)_{eμ}$ neutrino mass and dark matter~(DM) model to explain the recent DArk Matter Particle Explorer (DAMPE) data, which feature an excess on the cosmic ray electron plus positron flux around 1.4 TeV. Only the first two lepton generations of the Standard Model are charged under the new $U(1)_{eμ}$ gauge symmetry. A vector-like fermion $ψ$, which is our DM candidate, annihilates into $e^{\pm}$ and $μ^{\pm}$ via the new gauge boson $Z'$ exchange and accounts for the DAMPE excess. We have found that the data favors a $ψ$ mass around 1.5~TeV and a $Z'$ mass around 2.6~TeV…
Charged lepton flavor violating decays with a pair of light dark matter and muonium invisible decay
South China Normal University（华南师范大学）；Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Nuclear Science（广东省基础与应用基础研究基金委物质结构与基本相互作用卓越中心，广东省核科学重点实验室）
We present a new mechanism of Baryogenesis and dark matter production in which both the dark matter relic abundance and the baryon asymmetry arise from neutral $B$ meson oscillations and subsequent decays. This set-up is testable at hadron colliders and $B$-factories. In the early Universe, decays of a long lived particle produce $B$ mesons and anti-mesons out of thermal equilibrium. These mesons/anti-mesons then undergo CP violating oscillations before quickly decaying into visible and dark sector particles. Dark matter will be charged under Baryon number so that the visible sector baryon asy…
A resonance in the neutralino-nucleus elastic scattering cross section is usually purported when the neutralino-sbottom mass difference m_sbottom-m_chi is equal to the bottom quark mass m_b ~ 4 GeV. Such a scenario has been discussed as a viable model for light (~ 10 GeV) neutralino dark matter as explanation of possible DAMA and CoGeNT direct detection signals. Here we give physical and analytical arguments showing that the sbottom resonance may actually not be there. In particular, we show analytically that the one-loop gluon-neutralino scattering amplitude has no pole at m_sbottom=m_chi+m_b…
