Soft Leptogenesis without singlet

Low scale leptogenesis with an SU(2)_L singlet scalar

We consider thermal leptogenesis as the origin of the matter-antimatter asymmetry of the Universe. Some phenomenologically unpleasant features of the usual leptogenesis scenario are reviewed. We propose a minimal alternative, which makes use of a charged scalar $δ^+$, singlet under $SU(2)_L$. Such particle is contained in natural extensions of the Standard Model. The lepton asymmetry is generated by the decays of a right-handed neutrino into $δ^+$ and a right-handed charged lepton and it turns out to be sufficiently large for scales as low as $\sim$ TeV. The phenomenological signatures at coll…

Electroweak Resonant Leptogenesis in the Singlet Majoron Model

We study resonant leptogenesis at the electroweak phase transition in the singlet Majoron model with right-handed neutrinos. We consider a scenario, where the SM gauge group and the lepton number break down spontaneously during a second-order electroweak phase transition. We calculate the flavour- and temperature-dependent leptonic asymmetries, by including the novel contributions from the transverse polarisations of the W+/- and Z bosons. The required resummation of the gauge-dependent off-shell heavy-neutrino self-energies is consistently treated within the gauge-invariant framework of the P…

Leptogenesis implications in models with Abelian family symmetry and one extra real Higgs singlet

We show that the neutrino models, as suggested by Low, which have an additional Abelian family symmetry and a real Higgs singlet to the default see-saw do not hinder the possibility of successful thermal leptogenesis. For these models (neglecting radiative effects), we have investigated the situation of strong washout in both the one-flavor approximation and when flavor effects are included. The result is that while such models predict that theta_{13}=0 and that one light neutrino to be massless, they do not modify or provide significant constraints on the typical leptogenesis scenario where t…

Low-scale leptogenesis assisted by a real scalar singlet

Standard thermal leptogenesis in the type-I seesaw model requires very heavy right-handed neutrinos (RHNs). This makes it hard to probe this scenario experimentally and results in large radiative corrections to the Higgs boson mass. In this paper, we demonstrate that the situation is considerably different in models that extend the Higgs sector by a real scalar singlet. Based on effective-theory arguments, the extra scalar is always allowed to couple to the heavy neutrinos via singlet Yukawa terms. This opens up new RHN decay channels leading to larger $CP$ violation as well as to a stronger d…

Low Scale Leptogenesis and Dark Matter Candidates in an Extended Seesaw Model

We consider a variant of seesaw mechanism by introducing extra singlet neutrinos and singlet scalar boson, and show how low scale leptogenesis is successfully realized in this scenario. We examine if the newly introduced neutral particles, either singlet Majorana neutrino or singlet scalar boson, can be a candidate for dark matter. We also discuss the implications of the dark matter detection through the scattering off the nucleus of the detecting material on our scenarios for dark matter. In addition, we study the implications for the search of invisible Higgs decay at LHC, which may serve as…

Soft leptogenesis in the NMSSM with a singlet right-handed neutrino superfield

In this work, we explore soft leptogenesis in the NMSSM framework extended by a right-handed neutrino superfield. We calculate the CP asymmetry, $\varepsilon$, and find it to be non-zero at tree-level without using thermal effects for the final state particles. This is in contrast to soft leptogenesis in the MSSM extended by a right-handed neutrino superfield where thermal effects are essential. The difference arises due to the presence of a 3-body decay of the sneutrino in the NMSSM that violates lepton number at tree-level. Apart from this, we also find that $\varepsilon\neq 0$ if the additi…

Leptogenesis with Linear, Inverse or Double Seesaw

The left-right symmetric model with doublet and bi-doublet Higgs scalars can accommodate linear, inverse or double seesaw for generating small neutrino masses in the presence of three singlet fermions. If the singlet fermions have small Majorana masses, they can form three pairs of quasi-degenerate Majorana fermions with three right-handed neutrinos. The decays of the quasi-degenerate Majorana fermions can realize the resonant leptogenesis. Alternatively, the right-handed neutrinos can obtain seesaw suppressed Majorana masses if the singlet fermions are very heavy. In this case leptogenesis, w…

A model realizing inverse seesaw and resonant leptogenesis

We construct a model realizing the inverse seesaw mechanism. The model has two types of gauge singlet fermions in addition to right-handed neutrinos. A required Majorana mass scale (keV scale) for generating the light active neutrino mass in the conventional inverse seesaw can be naturally explained by a "seesaw" mechanism between the two singlet fermions in our model. We find that our model can decrease the magnitude of hierarchy among the mass parameters by $\mathcal{O}(10^4)$ from that in the conventional inverse seesaw model. We also show that a successful resonant leptogenesis occurs for …

Hybrid seesaw leptogenesis and TeV singlets

The appealing feature of inverse seesaw models is that the Standard Model (SM) neutrino mass emerges from the exchange of TeV scale singlets with sizable Yukawa couplings, which can be tested at colliders. However, the tiny Majorana mass splitting between TeV singlets, introduced to accommodate small neutrino masses, is left unexplained. Moreover, we argue that these models suffer from a structural limitation that prevents a successful leptogenesis if one insists on having unsuppressed Yukawa couplings and TeV scale singlets. In this work we propose a hybrid seesaw model, where we replace the …

Minimal Flavor Violation in the Minimal U(1)_{B-L} Model and Resonant Leptogenesis

We investigate the resonant leptogenesis scenario in the minimally $U(1)_{B-L}$ extended standard model with minimal flavor violation. In our model, the $U(1)_{B-L}$ gauge symmetry is broken at the TeV scale and standard model singlet neutrinos gain Majorana masses of order TeV. In addition, we introduce a flavor symmetry on the singlet neutrinos at a scale higher than TeV. The flavor symmetry is explicitly broken by the neutrino Dirac Yukawa coupling, which induces splittings in the singlet neutrino Majorana masses at lower scales through renormalization group evolutions. We call this setup "…

Testing quasi-Dirac leptogenesis through neutrino oscillations

The lightness of the Standard Model (SM) neutrinos could be understood if their masses were to be generated by new physics at a high scale, through the so-called seesaw mechanism involving heavy fermion singlets. If new physics violates baryon minus lepton number by only a small amount, the heavy fermion singlets as well as the SM neutrinos split into pairs of quasi-Dirac states. At the scale of the fermion singlets, this quasi-Diracness allows to enhance CP violation in their decays and the cosmic matter-antimatter asymmetry can be successfully generated through resonant leptogenesis. At lowe…

小尺度轻子生成与共振热轻子味相干

Low-Scale Leptogenesis from Resonant Thermal Lepton Flavour Coherences

本文提出一种新的小尺度轻子生成机制，通过共振热轻子味相干在二级循环中增强，适用于狄拉克和马约拉纳单态中微子，无需依赖准简并性。

High-scale leptogenesis with three-loop neutrino mass generation and dark matter

We demonstrate a common origin for high-scale leptogenesis and three-loop neutrino mass generation. Specifically we extend the standard model by two real singlet scalars, two singly charged scalars carrying different lepton numbers and two or more singlet fermions with Majorana masses. Our model respects a softly broken lepton number and an exactly conserved $Z_2^{}$ discrete symmetry. Through the lepton-number-violating decays of the real scalars and then the lepton-number-conserving decays of the charged scalars, we can obtain a lepton asymmetry stored in the standard model leptons. This lep…

Dirac Leptogenesis in extended nMSSM

We show that a version of the nearly Minimal Supersymmetric Standard Model (nMSSM), extended only in the singlet sector to include the additional superfields of right-handed neutrinos and very heavy Dirac particles conserving $B-L$, admits a viable scenario for Dirac leptogenesis and naturally small Dirac neutrino masses. The origin of the ($B-L$)-conserving high singlet neutrino scale and the desired supersymmetry breaking terms is associated with dynamical supersymmetry breaking in the hidden sector.

Low scale leptogenesis in a hybrid model of the scotogenic type I and III seesaw

The scotogenic type I and type III seesaw models are good candidates to explain the existence of neutrino masses and dark matter simultaneously. However, since triplet fermions have SU(2) gauge interaction, they cannot be out of equilibrium before the electroweak symmetry breaking. Thus, leptogenesis seems to be difficult within a framework of the pure type III seesaw model. Some extension seems to be required to solve this fault. A model extended by introducing a singlet fermion could be such a simple example. If the singlet fermion is in the thermal equilibrium even for its extremely small n…

A dark clue to seesaw and leptogenesis in a pseudo-Dirac singlet doublet scenario with (non)standard cosmology

We propose an appealing alternative scenario of leptogenesis assisted by dark sector which leads to the baryon asymmetry of the Universe satisfying all theoretical and experimental constraints. The dark sector carries a non minimal set up of singlet doublet fermionic dark matter extended with copies of a real singlet scalar field. A small Majorana mass term for the singlet dark fermion, in addition to the typical Dirac term, provides the more favourable dark matter of pseudo-Dirac type, capable of escaping the direct search. Such a construction also offers a formidable scope to radiative gener…

Phenomenological Consequences of Soft Leptogenesis

Soft supersymmetry breaking terms involving heavy singlet sneutrinos can be the dominant source of leptogenesis. The relevant range of parameters is different from standard leptogenesis: a lighter Majorana mass, M < 10^9 GeV (allowing a solution of the gravitino problem), and smaller Yukawa couplings, Y_N < 10^{-4}. We investigate whether the various couplings of the singlet sneutrinos, which are constrained by the requirement of successful `soft leptogenesis', can have observable phenomenological consequences. Specifically, we calculate the contributions of the relevant soft supersymmetric br…

Leptogenesis Bound on Spontaneous Symmetry Breaking of Global Lepton Number

We propose a new class of leptogenesis bounds on the spontaneous symmetry breaking of global lepton number. These models have a generic feature of inducing new lepton number violating interactions, due to the presence of the Majorons. We analyzed the singlet Majoron model with right-handed neutrinos and find that the lepton number should be broken above 10^5 GeV to realize a successful leptogenesis because the annihilations of the right-handed neutrinos into the massless Majorons and into the standard model Higgs should go out of equilibrium before the sphaleron process is over. We then argue …

New Ways to Soft Leptogenesis

Soft supersymmetry breaking terms involving heavy singlet sneutrinos provide new sources of lepton number violation and of CP violation. In addition to the CP violation in mixing, investigated previously, we find that `soft leptogenesis' can be generated by CP violation in decay and in the interference of mixing and decay. These additional ways to leptogenesis can be significant for a singlet neutrino Majorana mass that is not much larger than the supersymmetry breaking scale, $M < 100 m_{SUSY}$. In contrast to CP violation in mixing, for some of these new contributions the sneutrino oscillati…

具有自发破缺CP的混合跷跷板模型中的中微子质量与轻子生成

Neutrino mass and leptogenesis in a hybrid seesaw model with a spontaneously broken CP

该研究提出结合I型、II型跷跷板的混合中微子质量模型，以单态标量复真空期望值自发破缺CP，可同时解释中微子振荡与重子不对称，还分析了近简并场驱动的混合轻子生成情形。

Scalar-singlet assisted leptogenesis with CP violation from the vacuum

In the vanilla type-I seesaw leptogenesis scenario, CP violation required to generate the lepton asymmetries in the heavy Majorana neutrino decays stem from complex Dirac-type Yukawa couplings. In this paper we explore the case in which that CP violation originates from the vacuum expectation value of a complex scalar singlet at a very high scale. This non-trivial CP-violating phase can be successfully communicated to the low-energy neutrino sector via the heavy neutrino portal. The new scalar-singlet degrees of freedom generate new contributions to the CP asymmetries relevant for leptogenesis…

Scattering Rates For Leptogenesis: Damping of Lepton Flavour Coherence and Production of Singlet Neutrinos

Using the Closed-Time-Path approach, we perform a systematic leading order calculation of the relaxation rate of flavour correlations of left-handed Standard Model leptons. This quantity is of pivotal relevance for flavoured Leptogenesis in the Early Universe, and we find it to be 5.19*10^-3 T at T=10^7 GeV and 4.83*10^-3 T at T=10^13 GeV. These values apply to the Standard Model with a Higgs-boson mass of 125 GeV. The dependence of the numerical coefficient on the temperature T is due to the renormalisation group running. The leading linear and logarithmic dependencies of the flavour relaxati…

Dirac-Phase Thermal Leptogenesis in the extended Type-I Seesaw Model

Motivated by the fact that the Dirac phase in the PMNS matrix is the only CP-violating parameter in the leptonic sector that can be measured in neutrino oscillation experiments, we examine the possibility that it is the dominant source of CP violation for leptogenesis caused by the out-of-equilibrium decays of heavy singlet fermions. We do so within a low-scale extended type-I seesaw model, featuring two Standard Model singlet fermions per family, in which lepton number is approximately conserved such that the heavy singlet neutrinos are pseudo-Dirac. We find that this produces a predictive mo…

单态-三重态暗生模型中的低标度轻子生成

Low Scale Leptogenesis in Singlet-Triplet Scotogenic Model

本研究在单态-三重态暗生模型中探索低标度轻子生成的可能性，通过引入三种具有特定质量等级的重费米子，将轻子生成标度降至TeV量级，同时可解释W玻色子质量异常，且能被中微子质量测量实验检验。

Non-thermal leptogenesis with distinct CP violation and minimal dark matter

We demonstrate a unified scenario for neutrino mass, baryon asymmetry, dark matter and inflation. In addition to a fermion triplet for the so-called minimal dark matter, we extend the standard model by three heavy fields including a scalar singlet, a fermion triplet and a fermion singlet/Higgs triplet. The heavy scalar singlet, which is expected to drive an inflation, and the dark matter fermion triplet are odd under an unbroken $Z_2^{}$ discrete symmetry, while the other fields are all even. The heavy fermion triplet offers a tree-level type-III seesaw and then mediates a three-body decay of …

Leptogenesis, radiative neutrino masses and inert Higgs triplet dark matter

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…

Neutrino helicity asymmetries in leptogenesis

It is pointed out that the heavy singlet neutrinos characteristic of leptogenesis develop asymmetries in the abundances of the two helicity states as a result of the same mechanism that generates asymmetries in the standard lepton sector. Neutrinos and standard leptons interchange asymmetries in collisions with each other. It is shown that an appropriate quantum number, B-L', combining baryon, lepton and neutrino asymmetries, is not violated as fast as the standard B-L. This suppresses the washout effects relevant for the derivation of the final baryon asymmetry. One presents detailed calculat…

通过暗物质共湮灭实现轻子生成

Leptogenesis from Dark Matter Coannihilation

本文提出通过暗物质共湮灭实现轻子生成，结合I型锯齿模型扩展，提供对暗物质丰度的直接解释。

Leptogenesis from Soft Supersymmetry Breaking (Soft Leptogenesis)

Soft leptogenesis is a scenario in which the cosmic baryon asymmetry is produced from a lepton asymmetry generated in the decays of heavy sneutrinos (the partners of the singlet neutrinos of the seesaw) and where the relevant sources of CP violation are the complex phases of soft supersymmetry-breaking terms. We explain the motivations for soft leptogenesis, and review its basic ingredients: the different CP-violating contributions, the crucial role played by thermal corrections, and the enhancement of the efficiency from lepton flavour effects. We also discuss the high temperature regime $T >…

Leptogenesis from oscillations and dark matter

An extension of the Standard Model with Majorana singlet fermions in the 1-100 GeV range can give rise to a baryon asymmetry at freeze-in via the CP-violating oscillations of these neutrinos: this is the well known ARS mechanism. In this paper we consider possible extensions of the minimal ARS scenario that can account not only for successful leptogenesis but also explain other open problems such as dark matter. We find that an extension in the form of a weakly coupled B-L gauge boson, an invisible QCD axion model, and the singlet majoron model can simultaneously account for dark matter and th…

Soft leptogenesis in the inverse seesaw model

We consider leptogenesis induced by soft supersymmetry breaking terms ("soft leptogenesis"), in the context of the inverse seesaw mechanism. In this model there are lepton number (L) conserving and L-violating soft supersymmetry-breaking B-terms involving the singlet sneutrinos which, together with the -- generically small-- L-violating parameter responsible of the neutrino mass, give a small mass splitting between the four singlet sneutrino states of a single generation. In combination with the trilinear soft supersymmetry breaking terms they also provide new CP violating phases needed to gen…

Extended double seesaw model for neutrino mass spectrum and low scale leptogenesis

We consider a variant of seesaw mechanism by introducing extra singlet neutrinos, with which we show how the low scale leptogenesis is realized without imposing the tiny mass splitting between two heavy Majorana neutrinos required in the resonant leptogenesis. Thus, we can avoid the so-called gravitino problem when our scenario is supersymmetrized. We show that an introduction of the new singlet fermion leads to a new contribution which can enhance the lepton asymmetry for certain range of parameter space. We also examine how both the light neutrino mass spectrum and relatively light sterile n…

From high-scale leptogenesis to low-scale one-loop neutrino mass generation

We show that a high-scale leptogenesis can be consistent with a low-scale one-loop neutrino mass generation. Our models are based on the SU(3)_c\times SU(2)_L\times U(1)_Y\times U(1)_{B-L} gauge groups. Except a complex singlet scalar for the U(1)_{B-L} symmetry breaking, the other new scalars and fermions (one scalar doublet, two or more real scalar singlets/triplets and three right-handed neutrinos) are odd under an unbroken Z_2 discrete symmetry. The real scalar decays can produce an asymmetry stored in the new scalar doublet which subsequently decays into the standard model lepton doublets…

Observable Consequences of Partially Degenerate Leptogenesis

In the context of the seesaw mechanism, it is natural that the large solar and atmospheric neutrino mixing angles originate separately from large 2 by 2 mixings in the neutrino and charged-lepton sectors, respectively, and large mixing in the neutrino couplings is in turn more plausible if two of the heavy singlet neutrinos are nearly degenerate. We study the phenomenology of this scenario, calculating leptogenesis by solving numerically the set of coupled Boltzmann equations for out-of-equilibrium heavy singlet neutrino decays in the minimal supersymmetric seesaw model. The near-degenerate ne…

Dark Sector Assisted Low Scale Leptogenesis from Three Body Decay

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…

Baryogenesis via Leptogenesis from Asymmetric Dark Matter and radiatively generated Neutrino mass

We propose an extension of the standard model (SM) by including a dark sector comprising of three generations of heavy right-handed neutrinos, a singlet scalar and a singlet Dirac fermion, where the latter two particles are stable and are viable candidates of dark matter (DM). In the early Universe, the CP-violating out-of-equilibrium decay of heavy right-handed neutrinos to singlet Dirac fermion and scalar in the dark sector generates a net DM asymmetry. The latter is then transported to the visible sector via a dimension eight operator which conserves $B-L$ symmetry and is in thermal equilib…

Natural Seesaw and Leptogenesis from Hybrid of High-Scale Type I and TeV-Scale Inverse

We develop an extension of the basic inverse seesaw model which addresses simultaneously two of its drawbacks, namely, the lack of explanation of the tiny Majorana mass term $μ$ for the TeV-scale singlet fermions and the difficulty in achieving successful leptogenesis. Firstly, we investigate systematically leptogenesis within the inverse (and the related linear) seesaw models and show that a successful scenario requires either small Yukawa couplings, implying loss of experimental signals, and/or quasi-degeneracy among singlets mass of different generations, suggesting extra structure must be …

Dark matter and low scale leptogenesis in a flavor symmetric neutrino two Higgs doublet model($ν$2HDM)

We have studied dark matter (DM) phenomenology, neutrinoless double beta decay (NDBD) and realized low scale leptogenesis in an extension of Standard Model(SM) with three neutral fermions, a scalar doublet and a dark sector incorporating a singlet scalar and a Dirac singlet fermion. A generic model based on $A_4\times Z_4$ flavor symmetry including five flavons is used to explain both normal and inverted hierarchy mass patterns of neutrino and also to accommodate the dark matter mass. In this extension of the $ν$2HDM, the effective neutrino mass observed in $0νββ$ is well within the experiment…

Soft Leptogenesis

We study ``soft leptogenesis'', a new mechanism of leptogenesis which does not require flavour mixing among the right-handed neutrinos. Supersymmetry soft-breaking terms give a small mass splitting between the CP-even and CP-odd right-handed sneutrino states of a single generation and provide a CP-violating phase sufficient to generate a lepton asymmetry. The mechanism is successful if the lepton-violating soft bilinear coupling is unconventionally (but not unnaturally) small. The values of the right-handed neutrino masses predicted by soft leptogenesis can be low enough to evade the cosmologi…

Probing High Scale Dirac Leptogenesis via Gravitational Waves from Domain Walls

We propose a novel way of probing high scale Dirac leptogenesis, a viable alternative to canonical leptogenesis scenario where the total lepton number is conserved, keeping light standard model (SM) neutrinos purely Dirac. The simplest possible seesaw mechanism for generating light Dirac neutrinos involve heavy singlet Dirac fermions and a singlet scalar. In addition to unbroken global lepton number, a discrete $Z_2$ symmetry is imposed to forbid direct coupling between right and left chiral parts of light Dirac neutrino. Generating light Dirac neutrino mass requires the singlet scalar to acqu…

Leptogenesis With Many Neutrinos

We consider leptogenesis in scenarios with many neutrino singlets. We find that the lower bound for the reheating temperature can be significantly relaxed with respect to the hierarchical three neutrino case. We further argue that the upper bound for the neutrino mass scale from leptogenesis gets significantly lifted in these scenarios. As a specific realization, we then discuss an extra-dimensional model, where the large number of neutrinos is provided by Kaluza-Klein excitations.

Tri-Resonant Leptogenesis

We present a class of leptogenesis models where the light neutrinos acquire their observed mass through a symmetry-motivated construction. We consider an extension of the Standard Model, which includes three singlet neutrinos which have mass splittings comparable to their decay widths. We show that this tri-resonant structure leads to an appreciable increase in the observed CP asymmetry over that found previously in typical bi-resonant models. To analyse such tri-resonant scenarios, we solve a set of coupled Boltzmann equations, crucially preserving the variations in the relativistic degrees o…

Low-scale leptogenesis and soft supersymmetry breaking

We investigate the possibility of low-scale leptogenesis in the minimal supersymmetric standard model extended with right handed (s)neutrinos. We demonstrate that successful leptogenesis can be easily achieved at a scale as low as ~ TeV where lepton number and CP violation comes from soft supersymmetry breaking terms. The scenario is shown to be compatible with neutrino masses data.

Early Universe effective theories: The Soft Leptogenesis and R-Genesis Cases

We discuss the effective theory appropriate for studying soft leptogenesis at temperatures T>10^7 GeV. In this regime, the main source of the B-L asymmetry is the CP asymmetry of a new anomalous R-charge that couple to generalized anomalous electroweak processes. Baryogenesis thus occurs mainly through R-genesis, and with an efficiency that can be up to two orders of magnitude larger than in usual estimates. Contrary to common belief, a sizeable baryon asymmetry is generated also when thermal corrections to the CP asymmetries in sneutrino decays are neglected which, in soft leptogenesis, imply…

Singlet Fermion Assisted Dominant Seesaw with Lepton Flavor and Number Violations and Leptogenesis

In a recent review Mohapatra has discussed how type-I seesaw mechanism suppressed by fine tuning of Yukawa couplings, or specific textures of associated fermion mass matrices, can form the basis of neutrino masses in TeV scale $W_R$ boson models. In this paper we review recent works in another class of theories where the added presence of fermion singlets manifesting as sterile neutrinos render the type-I seesaw contribution vanishing but extended seesaw dominant where the light neutrino mass formula is same as the classic inverse seesaw but all massive neutrinos are Majorana fermions. We also…

Electron EDM and soft leptogenesis in supersymmetric B-L extension of the standard model

We analyze the connection between electric dipole moment of the electron and the soft leptogenesis in supersymmetric $B-L$ extension of the standard model. In this model, the $B-L$ symmetry is radiatively broken at TeV scale. Therefore, it is a natural framework for low scale seesaw mechanism and also for implementing the soft leptogenesis. We show that the phases of trilinear soft SUSY breaking couplings $A$, which are relevant for the lepton asymmetry, are not constrained by the present experimental bounds on electric dipole moment. As in the MSSM extended with right-handed neutrinos, succes…

Late Leptogenesis from Radiative Soft Terms

We point out that the so-called ``soft leptogenesis'' can occur at TeV scale if the $B$ term is generated through radiative corrections which involve two-loop diagrams with the gaugino exchange. This mechasnism requires the non-trivial CP phase, ${Im}(A m_{1/2}^*)\neq 0$, and can naturally explain the observed baryon asymmetry of the universe associated with the TeV scale seesaw mechanism. Such a low scale leptogenesis would be a promising option in view of the tight upper limit on the reheat temperature avoiding the gravitino problem in supergravity models.

Leptogenesis without violation of B-L

We study the possibility of generating the observed baryon asymmetry via leptogenesis in the decay of heavy Standard Model singlet fermions which carry lepton number, in a framework without Majorana masses above the electroweak scale. Such scenario does not contain any source of total lepton number violation besides the Standard Model sphalerons, and the baryon asymmetry is generated by the interplay of lepton flavour effects and the sphaleron decoupling in the decay epoch.

Natural soft leptogenesis

Successful soft leptogenesis requires small B-terms for the right-handed sneutrinos and a large CP violating phase between the A- and B-terms. We show that this situation is realized naturally within the framework of gauge mediated supersymmetry breaking. The A-term is dominated by contribution from gauge mediation, while supergravity effects are more important for the B-term. The different origins naturally explain simultaneously the smallness of the B-term and the large CP violating phase. The most stringent bounds on the model come from the cosmological gravitino problem. We find a viable p…

Soft Leptogenesis and Gravitino Dark Matter in Gauge Mediation

We study soft leptogenesis in gauge mediated supersymmetry breaking models with an enhanced A-term for the right-handed neutrino. We find that this scenario can explain the baryon asymmetry of the present universe, consistently with the gravitino dark matter for a wide range of gravitino mass m_{3/2}=O(MeV)-O(GeV). We also propose an explicit model which induces the necessary A-term for the right-handed neutrino.

单态-双重态暗物质诱导的辐射中微子质量与TeV尺度轻子生成

Singlet-doublet dark matter induced radiative neutrino mass and TeV scale leptogenesis

该研究探讨单态-双重态暗物质模型中TeV尺度轻子生成，通过马约拉纳和狄拉克两种设置实现辐射中微子质量，并满足暗物质遗迹与对撞机信号约束。

暗物质驱动的中微子门户低尺度轻子生成

Dark Matter-Driven Low-Scale Leptogenesis via Neutrino Portal

提出一种标准模型扩展框架，通过暗物质与轻子生成的直接关联，利用右手中微子衰变和散射过程中的CP破坏，统一解释物质-反物质不对称性和暗物质丰度。

Purely Flavored Leptogenesis

We study a model for leptogenesis in which the total CP asymmetries in the decays and scatterings involving the SU(2) singlet seesaw neutrinos $N_α$ vanish ($ε_{N_α}=0$). Leptogenesis is possible due to non-vanishing CP violating lepton flavor asymmetries, realizing a situation in which the baryon asymmetry is due exclusively to flavor effects. We study the production of a net lepton asymmetry by solving the Boltzmann equations specific to this model, and we show that successful leptogenesis can be obtained at a scale as low as the TeV. We also discuss constraints on the model parameter space …

Neutrino mass and low-scale leptogenesis in a testable SUSY SO(10) model

It is shown that a supersymmetric SO(10) model extended with fermion singlets can accommodate the observed neutrino masses and mixings as well as generate the desired lepton asymmetry in concordance with the gravitino constraint. A necessary prediction of the model is near-TeV scale doubly-charged Higgs scalars which should be detectable at the LHC.