A Dirac fermion carrying an integral weak isospin and the vanishing hypercharge is considered as its neutral component can be a promising dark matter candidate (called the minimal dark matter) whose mass is of order 100 GeV. While the symmetric population annihilates away due to a rapid gauge interaction, its asymmetric abundance is supposed to be produced by the decay of a right-handed neutrino superfield in the supersymmetric type I seesaw mechanism. The efficiencies for generating the dark matter and lepton asymmetries are calculated by solving a set of approximate Boltzmann equations. A spectacular feature of this scenario is the existence of a long-lived singly- or multiply-charged scalar and a shorter-lived singly-charged fermion whose tracks can be readily looked for at the LHC.
Central University of Himachal Pradesh（喜马偕尔邦中央大学）；Indian Institute of Technology Guwahati（印度理工学院古瓦哈提分校）；University of Pittsburgh（匹兹堡大学）；Washington University in St. Louis（圣路易斯华盛顿大学）；Johannes Gutenberg-Universität Mainz（美因茨约翰内斯·古腾堡大学）；Pragjyotish College（普拉吉约蒂什学院）
We study the cosmology and phenomenology of freeze-in baryogenesis via dark-matter oscillations, taking the dark matter to couple to Standard Model leptons. We investigate viable models both with and without a $Z_2$ symmetry under which all new fields are charged. Lepton flavor effects are important for leptogenesis in these models, and we identify scenarios in which the baryon asymmetry is parametrically distinct from and enhanced relative to leptogenesis from sterile neutrino oscillations. The models we study predict the existence of new, electroweak-charged fields, and can be tested by a co…
We present a new realization of asymmetric dark matter in which the dark matter and lepton asymmetries are generated simultaneously through two-sector leptogenesis. The right-handed neutrinos couple both to the Standard Model and to a hidden sector where the dark matter resides. This framework explains the lepton asymmetry, dark matter abundance and neutrino masses all at once. In contrast to previous realizations of asymmetric dark matter, the model allows for a wide range of dark matter masses, from keV to 10 TeV. In particular, very light dark matter can be accommodated without violating ex…
We review the viability of the sterile neutrino hypothesis in accounting for three observational problems of the Standard Model of particle physics: neutrino masses and lepton mixing, dark matter and the baryon asymmetry of the Universe. We present two alternative scenarios for the implementation of the sterile fermion hypothesis: the $ν$MSM and the Inverse Seesaw.
A triplet dark matter candidate from thermal leptogenesis is considered with building a model. The model is based on the standard two Higgs doublet model and seesaw mechanism with Higgs triplets. The parameters (couplings and masses) are adjusted for the observed small neutrino mass and the leptogenesis. Dark matter particles can annihilate and decay in this model. The time evolution of the dark matter number is governed by (co)annihilations in the expanding universe, and its mass is constrained by the observed relic density. The dark matter can decay into final states with three leptons (two …
We study the possibility of realising leptogenesis from three body decay, dark matter (DM) and neutrino mass in a minimal framework. We propose a first of its kind model to implement the idea of leptogenesis from three body decay where CP asymmetry arises from interference of multiple $1 \rightarrow 3$ diagrams using resummed propagators along with DM. The standard model is extended by three heavy singlet fermions, one scalar singlet and one scalar doublet with appropriate discrete charges. Two of these singlet fermions not only play non-trivial roles in generating light neutrino mass at radia…
We discuss asymmetric or symmetric dark matter candidate in the supersymmetric Dirac leptogenesis scenario. By introducing a singlet superfield coupling to right-handed neutrinos, the overabundance problem of dark matter can be evaded and various possibilities for dark matter candidate arise. If the singlino is the lightest supersymmetric particle (LSP), it becomes naturally asymmetric dark matter. On the other hand, the right-handed sneutrino is a symmetric dark matter candidate whose relic density can be determined by the usual thermal freeze-out process. The conventional neutralino or gravi…
Supersymmetric models with radiatively-driven electroweak naturalness require light higgsinos of mass ~ 100-300 GeV. Naturalness in the QCD sector is invoked via the Peccei-Quinn (PQ) axion leading to mixed axion-higgsino dark matter. The SUSY DFSZ axion model provides a solution to the SUSY mu problem and the Little Hierarchy μ<< m_{3/2} may emerge as a consequence of a mismatch between PQ and hidden sector mass scales. The traditional gravitino problem is now augmented by the axino and saxion problems, since these latter particles can also contribute to overproduction of WIMPs or dark radiat…
We present a minimal framework of $U(1)_{B-L}$ gauge extension of the Standard Model explaining dark matter abundance and matter-antimatter asymmetry simultaneously through an attractive mechanism of TeV scale WIMPy leptogenesis, testable at the current and next generation of colliders. This framework can also explain small neutrino masses via a radiative mechanism. One of the key predictions of this model is an enhanced rate for lepton flavor violating decay $μ\rightarrow e γ$ within the sensitivity reach of next generation experiments.
The Majoron Cosmological Window: Dark Matter and Thermal Leptogenesis
Institute for Particle Physics Phenomenology, Department of Physics, Durham University（达勒姆大学粒子物理现象学研究所）；Instituto de Física Teórica UAM/CSIC, Universidad Autónoma de Madrid（马德里自治大学理论物理研究所UAM/CSIC）；Institute for Astroparticle Physics (IAP), Karlsruhe Institute of Technology (KIT)（卡尔斯鲁厄理工学院天体粒子物理研究所(IAP)）；Department of Physics, University of Basel（巴塞尔大学物理系）
We consider the possibility of simultaneously addressing the baryon asymmetry of the Universe, the dark matter problem and the neutrino mass generation in minimal extensions of the Standard Model via sterile fermions with (small) total lepton number violation. Within the framework of Inverse and Linear Seesaw models, the small lepton number violating parameters set the mass scale of the active neutrinos, the efficiency of leptogenesis through a small mass splitting between pairs of sterile fermions as well as the mass scale of a sterile neutrino dark matter candidate. We provide an improved pa…
The Dirac nature of the gauginos (and also the Higgsinos) can be realized in $R$-symmetric supersymmetry models. In this class of models, the Dirac bino (or wino) with a small mixture of the Dirac Higgsinos is a good dark matter candidate. When the seesaw mechanism with Higgs triplet superfields is implemented to account for the neutrino masses and mixing, the leptogenesis driven by the heavy triplet decay is shown to produce not only the matter-antimatter asymmetry but also the asymmetric relic density of the Dirac gaugino dark matter. The dark matter mass turns out to be controlled by the Yu…
We study the possibility of low scale leptogenesis along with dark matter (DM) in the presence of primordial black holes (PBH). For a common setup to study both leptogenesis and DM we consider the minimal scotogenic model which also explains light neutrino mass at radiative level. While PBH in the mass range of $0.1-10^5$ g can, in principle, affect leptogenesis, the required initial PBH fraction usually leads to overproduction of scalar doublet DM whose thermal freeze-out occurs before PBH evaporation. PBH can lead to non-thermal source of leptogenesis as well as dilution of thermally generat…
We propose a realization of mass varying neutrino dark energy in two extensions of the Standard Model (SM) with a dynamical neutrino mass related to the acceleron field while satisfying the naturalness. In the first scenario the SM is extended to include a TeV scale scalar Higgs triplet ($ξ$) and a TeV scale second Higgs doublet ($η$), while in the second scenario an extension of the SM with fermion triplet $(Σ)$ is considered. We also point out the possible leptogenesis mechanisms for simultaneously generating the observed baryon asymmetry of the universe in both the scenarios and discuss the…
We consider a simple extension of the Standard Model with two singlet scalar fields and three heavy right-handed neutrinos. One of the scalar fields serves as an MeV scale dark matter and its stability is ensured by the introduction of an extra $Z_2$ symmetry. The second scalar (which is even under the $Z_2$ symmetry) generates the mass term of the scalar, contributes to the $3 \rightarrow 2$ annihilation process required for the correct relic density of the dark matter and it also contributes to the leptogenesis. The right-handed neutrinos are responsible for the generation of light neutrino …
We analyze a scenario in which the lightest heavy neutrino $N_1$ is a dark matter candidate and the second- heaviest neutrino $N_2$ decays producing a lepton number. If $N_1$ were in thermal equilibrium, its energy density today would be much larger than that of the observed dark matter, so we consider energy injection by the decay of $N_2$. In this paper, we show the parameters of this scenario that give the correct abundances of dark matter and baryonic matter and also induce the observed neutrino masses. This model can explain a possible sterile neutrino dark matter signal of $M_1$=7 keV in…
We analyze leptogenesis in gauge extensions of the Standard Model with keV sterile neutrino dark matter. We find that both the observed dark matter abundance and the correct baryon asymmetry of the Universe can simultaneously emerge in these models. Both the dark matter abundance and the leptogenesis are controlled by the out of equilibrium decays of the same heavy right handed neutrino.
After a brief discussion of baryon and lepton number nonconservation, we review the status of thermal leptogenesis with GUT scale neutrino masses, as well as low scale alternatives with keV neutrinos as dark matter and heavy neutrino masses within the reach of the LHC. Recent progress towards a full quantum mechnical description of leptogenesis is described with resonant leptogenesis as an application. Finally, cosmological B-L breaking after inflation is considered as origin of the hot early universe, generating entropy, baryon asymmetry and dark matter.
We study the consequence of a non-standard cosmological epoch in the early universe on the generation of baryon asymmetry through leptogenesis as well as dark matter abundance. We consider two different non-standard epochs: one where a scalar field behaving like pressure-less matter dominates the early universe, known as early matter domination (EMD) scenario while in the second scenario, the energy density of the universe is dominated by a component whose energy density red-shifts faster than radiation, known as fast expanding universe (FEU) scenario. While a radiation dominated universe is r…
Many extensions of the Standard Model predict super-weakly interacting particles, which typically have to decay before Big Bang Nucleosynthesis (BBN). The entropy produced in the decays may help to reconcile thermal leptogenesis and BBN in scenarios with gravitino dark matter, which is usually difficult due to late decays of the next-to-lightest supersymmetric particle (NLSP) spoiling the predictions of BBN. We study this possibility for a general neutralino NLSP. We elaborate general properties of the scenario and strong constraints on the entropy-producing particle. As an example, we conside…
We study a scenario where both dark matter and heavy right handed neutrino (RHN) responsible for leptogenesis acquire masses by crossing the relativistic bubble walls formed as a result of a TeV scale supercooled first order phase transition (FOPT). While this leads to a large out-of-equilibrium abundance of right handed neutrino inside the bubble sufficient to produce the required lepton asymmetry, the dark matter being lighter can still remain in equilibrium with its relic being set by subsequent thermal freeze-out. A classical conformal symmetry ensures the origin of mass via FOPT induced b…
We study a two-loop induced radiative neutrino model at TeV scale with global $U(1)$ symmetry, in which we analyze dark matter and resonant leptogenesis. The model includes two kinds of dark matter candidates. We discuss what kind of dark matter can satisfy the observed relic density as well as the current direct detection bound, and be simultaneously compatible with the leptogenesis. We also discuss whether our resonant leptogenesis can be differentiated from the other scenarios at TeV scale or not.
We study the possibility of generating tiny Dirac neutrino masses at one loop level through the \textit{scotogenic} mechanism such that one of the particles going inside the loop can be a stable cold dark matter (DM) candidate. Majorana mass terms of singlet fermions as well as tree level Dirac neutrino masses are prevented by incorporating the presence of additional discrete symmetries in a minimal fashion, which also guarantee the stability of the dark matter candidate. Due to the absence of total lepton number violation, the observed baryon asymmetry of the Universe is generated through the…
We present a TeV scale model for leptogenesis where the origin of neutrino masses are independent of the scale of leptogenesis. As a result, the model could be extended to explain {\it dark matter, neutrino masses and leptogenesis at the TeV scale}. The most attractive feature of this model is that it predicts a few hundred GeV triplet Higgs scalar that can be tested at LHC or ILC.
It is proposed that dark matter is the origin of neutrino mass, thereby linking inexorably two undisputed (and seemingly unrelated) pieces of evidence for physics beyond the Standard Model. Leptogenesis at the TeV scale may also be possible, as well as a measurable contribution to the muon anomalous magnetic moment.
We propose a gauged $B-L$ extension of the standard model (SM) where light neutrinos are of Dirac type by virtue of tiny Yukawa couplings with the SM Higgs. To achieve leptogenesis, we include additional heavy Majorana fermions without introducing any $B-L$ violation by two units. An additional scalar doublet with appropriate $B-L$ charge can allow heavy fermion coupling with the SM leptons so that out of equilibrium decay of the former can lead to generation of lepton asymmetry. Due to the $B-L$ gauge interactions of the decaying fermion, the criteria of successful Dirac leptogenesis can also…
We propose an extension of the standard model with a $U(1)_{\rm B-L}$ global symmetry that accommodates radiative neutrino masses along with dark matter and leptogenesis. The observed matter antimatter asymmetry of the universe is generated through the leptogenesis route keeping the $U(1)_{\rm B-L}$ symmetry intact. The $B-L$ global symmetry is then softly broken, providing the sub-eV neutrino masses. The model then incorporates a MeV scale sterile neutrino like dark matter.
We consider a class of leptogenesis models in which the lepton asymmetry arises from dark matter annihilation processes which violate CP and lepton number. Importantly, a necessary one-loop contribution to the annihilation matrix element arises from absorptive final state interactions. We elucidate the relationship between this one-loop contribution and the CP-violating phase. As we show, the branching fraction for dark matter annihilation to leptons may be small in these models, while still generating the necessary asymmetry.
The nature of dark matter (DM) particles and the mechanism that provides their measured relic abundance are currently unknown. Likewise, the nature of the inflaton is unknown as well. We investigate the triplet seesaw model in an unified picture. At high energy scale, we consider Higgs inflation driven by an admixture of standard model and triplet Higgs fields, both coupled non-minimally to gravity. At intermediate and low energies we investigate vector like fermion doublet DM candidates with a charge asymmetry in the dark sector, which is generated by the same mechanism that provides the bary…
We consider a class of leptogenesis models in which the lepton asymmetry arises from dark matter annihilation processes which violate CP and lepton number. Importantly, a necessary one-loop contribution to the annihilation matrix element arises from absorptive final state interactions. We elucidate the relationship between this one-loop contribution and the CP-violating phase. As we show, the branching fraction for dark matter annihilation to leptons may be small in these models, while still generating the necessary asymmetry.
We study implications of thermal leptogenesis for the superparticle mass spectrum. A consistent picture is obtained if the lightest superparticle is the gravitino, which can be the dominant component of cold dark matter. In the case of a long-lived charged scalar lepton as next-to-lightest superparticle, supergravity can be tested at the next generation of colliders, LHC and ILC.
Within a supersymmetric (SUSY) type-I seesaw framework with flavor-blind universal boundary conditions, we study the consequences of requiring that the observed baryon asymmetry of the Universe be explained by either thermal or non-thermal leptogenesis. In the former case, we find that the parameter space is very constrained. In the bulk and stop-coannihilation regions of mSUGRA parameter space (that are consistent with the measured dark matter abundance), lepton flavor-violating (LFV) processes are accessible at MEG and future experiments. However, the very high reheat temperature of the Univ…
I suggest a new extension of the SM by introducing a dark sector which has several new particles and a local $U(1)_{D}$ symmetry. The dark particles bring about the new and interesting physics beyond the SM. The model can generate the tiny neutrino mass by a hybrid see-saw mechanism, achieve the leptogenesis at the TeV scale, and account for the cold dark matter. All of the three things collectively arise from the dark sector. In particular, it is very feasible to test the model predictions and probe the dark sector in near future experiments.
We explain the electron-positron excess reported by the DAMPE collaboration recently in a radiative Dirac seesaw model where a dark $U(1)_X$ gauge symmetry can (i) forbid the tree-level Yukawa couplings of three right-handed neutrinos to the standard model lepton and Higgs doublets, (ii) predict the existence of three dark fermions for the gauge anomaly cancellation, (iii) mediate a testable scattering of the lightest dark fermion off the nucleons. Our model can also accommodate a successful leptogenesis to generate the cosmic baryon asymmetry.
Numerous recent evidences for neutrino masses have established the leptogenesis mechanism as a very natural possible explanation for the baryon asymmetry of the Universe. The explicit realization of this mechanism depends on the neutrino mass model considered. If the right-handed type-I seesaw model of neutrino masses is certainly the most straightforward, it is not the only natural one, especially in the framework of explicit GUT realizations of the seesaw. In this review we discuss in detail the various seesaw scenarios that can implement the leptogenesis mechanism successfully, beyond the p…
We study a seesaw-type extension of the Standard Model in which the symmetry group is enlarged by a global U(1). We introduce adequate scalar and fermion representations which naturally explain the smallness of neutrino masses. With the addition of a viable scalar Dark Matter candidate, an original scenario of leptogenesis emerges. We solve the relevant set of Boltzmann equations and show how leptogenesis can be successfully implemented at the TeV scale. The constraints on the scalar mass spectrum are derived and the Dark Matter phenomenology is discussed.
We propose an interesting model of neutrino masses to realize leptogenesis and dark matter at the TeV scale. A real scalar is introduced to naturally realize the Majorana masses of the right-handed neutrinos. We also include a new Higgs doublet that contributes to the dark matter of the universe. The neutrino masses come from the vacuum expectation value of the triplet Higgs scalar. The right-handed neutrinos are not constrained by the neutrino masses and hence they could generate leptogenesis at the TeV scale without subscribing to resonant leptogenesis. In our model, all new particles could …
A scenario that relates the abundance of dark matter to the baryon asymmetry of the Universe is presented. In this scenario, based on a left-right extension of the Standard Model, dark matter is made of light, ~ 1 GeV, right-handed Majorana neutrinos.
We study a seesaw-type extension of the Standard Model in which the symmetry group is enlarged by a global U(1). We introduce adequate scalar and fermion representations which naturally explain the smallness of neutrino masses. With the addition of a viable scalar Dark Matter candidate, an original and successful scenario of leptogenesis emerges.
The scotogenic mechanism for radiative neutrino mass is generalized to include neutron-antineutron oscillation as well as proton decay. Dark matter is stabilized by extending the notion of lepton parity to matter parity. Leptogenesis is also a possible byproduct. This framework unifies the description of all these important, but seemingly unrelated, topics in physics beyond the standard model of particle interactions.
We investigate the possibility that dark matter and the baryon asymmetry of the Universe are generated by the same mechanism, following an idea initially proposed by V.A. Kuzmin and recently discussed by R. Kitano and I. Low. In our model, based on a left-right extension of the Standard Model, the baryon asymmetry is generated through leptogenesis and dark matter is made of relic stable right-handed neutrinos with mass ~ few GeV. Constraints on the model imply that this form of dark matter would unfortunately escape detection.
The framework for soft leptogenesis minimally extended with a DM sector is studied. A heavy singlet neutrino superfield acts as the source for (s)lepton asymmetry and by coupling to the singlet DM superfield it produces a DM particle density through decays. The nature of DM generated is twofold depending on whether the Yukawa and DM couplings are either small or large. With sufficiently small Yukawa and DM couplings DM annihilations into MSSM particles are slow and as a consequence all DM particles form the DM component. The solutions to Boltzmann equations are given and the dependence between…
We propose a new mechanism of TeV scale leptogenesis where the chemical potential of right-handed electron is passed on to the $B-L$ asymmetry of the Universe in the presence of sphalerons. The model has the virtue that the origin of neutrino masses are independent of the scale of leptogenesis. As a result, the model could be extended to explain {\it dark matter, dark energy, neutrino masses and leptogenesis at the TeV scale}. The most attractive feature of this model is that it predicts a few hundred GeV triplet Higgs scalar that can be tested at LHC or ILC.
We study the possibility of singlet fermion dark matter (DM) and successful leptogenesis in minimal scotogenic model which also provides a common origin of DM and light neutrino masses. In this scenario, where the standard model (SM) is extended by three gauge singlet fermions and one additional scalar doublet, all odd under an in-built $Z_2$ symmetry, the lightest singlet fermion which also happens to be the lightest $Z_2$ odd particle, can be either thermal or non-thermal DM candidate depending upon the strength of its couplings with SM leptons and the $Z_2$ odd scalar doublet. In both the s…
Observational evidences of nonzero neutrino masses and the existence of dark matter request physics beyond standard model. A model with extra scalars and leptonic vector-like fermions is introduced. By imposing a Z_2 symmetry, the neutrino masses as well as anomalous muon magnetic moment can be generated via one-loop effects at TeV-scale. An effort of explaining dark matter, Lithium problem, and leptogenesis is presented. This scenario can be tested at LHC and/or future experiments.
In this paper, we perform a detail analysis on leptogenesis and dark matter form low scale seesaw. In the framework of $ν$2HDM, we further introduce one scalar singlet $ϕ$ and one Dirac fermion singlet $χ$, which are charged under a $Z_2$ symmetry. Assuming the coupling of $χ$ is extremely small, it serves as a FIMP dark matter. The heavy right hand neutrinos $N$ provide a common origin for tiny neutrino mass (via seesaw mechanism), leptogenesis (via $N\to \ell_L Φ_ν^*,\bar{\ell}_L Φ_ν$) and dark matter (via $N\to χϕ$). With hierarchical right hand neutrino masses, the explicit calculation sho…
The evidence for dark matter signals a new class of particles at the TeV scale, which may manifest themselves indirectly through loop effects. In a simple model we show that these loop effects may be responsible for the enhanced muon anomalous magnetic moment, for the neutrino mass, as well as for leptogenesis in a novel way. This scenario can be verified at LHC experiments.
The seesaw and leptogenesis commonly depend on the masses of same particles, and thus are both realized at the same scale. In this work, we demonstrate a new possibility to realize a TeV-scale neutrino seesaw and a natural high-scale leptogenesis. We extend the standard model by two gauge-singlet scalars, a vector-like iso-doublet fermion and one iso-triplet Higgs scalar. Our model respects a softly broken lepton number and an exactly conserved $Z_2$ discrete symmetry. It can achieve three things altogether: (i) realizing a testable type-II seesaw at TeV scale with two nonzero neutrino mass-ei…
We extend the standard model by three types of inert fields including Majorana fermion singlets/triplets, real Higgs singlets/triplets and leptonic Higgs doublets. In the presence of a softly broken lepton number and an exactly conserved Z_2 discrete symmetry, these inert fields together can mediate a one-loop diagram for a Majorana neutrino mass generation. The heavier inert fields can decay to realize a successful leptogenesis while the lightest inert field can provide a stable dark matter candidate. As an example, we demonstrate the leptogenesis by the inert Higgs doublet decays. We also pe…
We propose an extension of the standard model, in which neutrinos are Dirac particles and their tiny masses originate from a one-loop radiative diagram. The new fields required by the neutrino mass-generation also accommodate the explanation for the matter-antimatter asymmetry and dark matter in the universe.
