We present preliminary results from a global study of the extended scalar singlet model with a fermionic dark matter (DM) candidate. In addition to requiring a successful electroweak baryogenesis, we combine constraints from the DM relic density, direct detection limits from PandaX-II experiment, electroweak precision observables and Higgs searches at colliders. In agreement with previous studies, we find that the model can simultaneously explain (at least a part of) the observed DM abundance and matter-antimatter asymmetry. The viable points often lead to strong gravitational wave (GW) signals that can potentially be probed at future GW experiments.
We study the possible gravitational wave signal and the viability of baryogenesis arising from the electroweak phase transition in an extension of the Standard Model (SM) by a scalar singlet field without a $\mathbb{Z}_2$ symmetry. We first analyze the velocity of the expanding true-vacuum bubbles during the phase transition, confirming our previous finding in the unbroken $\mathbb{Z}_2$ symmetry scenario, where the bubble wall velocity can be computed from first principles only for weak transitions with strength parameters $α\lesssim 0.05$, and the Chapman-Jouguet velocity defines the maximum…
Radiative neutrino masses in the singlet-doublet fermion dark matter model with scalar singlets
在单重态-二重态费米子暗物质模型中加入$Z_2$ -奇实单重态标量，可以在单圈水平上产生中微子质量和混合。在这项工作中，我们讨论了两个简化的暗物质模型的组合所产生的显着特点。当$Z_2$ -最轻的奇粒子是标量单态时，只要单态-二重态费米子混合足够小，$\operatorname{Br}(μ\to e γ)$是可以测量的。在这种情况下，类矢量费米子到标量的新衰变通道也可以在LHC上产生有趣的轻子加丢失的横能量信号。另一方面，在类二重态费米子暗物质的情况下，标量共湮灭导致遗迹密度的增加，这使得类二重态费米子暗物质的束缚降低。
Impact of vacuum stability, perturbativity and XENON1T on global fits of $\mathbb{Z}_2$ and $\mathbb{Z}_3$ scalar singlet dark matter
标量单重态暗物质是弱相互作用大质量粒子（WIMP）理论最简单、最具预测性的实现形式之一。尽管该模型受到最新实验数据的各个方向的约束，但它仍然具有可行的参数空间区域。标量单态的另一个引人注目的方面是它们稳定电弱真空的能力。事实上，纯量暗物质的模型并不是低能有效的理论，但在普朗克尺度下都是有效的。使用GAMBIT框架，我们提出了第一个全球性的适合，包括低能量的实验约束和理论约束，从紫外物理，考虑模型与一个标量单线带电荷下的$\mathbb{Z}_2$或$\mathbb{Z}_3$对称性。我们表明，如果该模型是满足所有的实验约束，完全稳定的电弱真空高尺度，并保持微扰这些尺度，一个是驱动到一个相对较小的区域的参数空间。这个区域的希格斯-门耦合略小于1，暗物质质量为1至2 TeV，核散射截面约为10 $^{-45}$ cm $^2$，与自旋无关。
We match the electroweak chiral Lagrangian with two singlet scalars to the next-to-minimal composite Higgs model with $ SO(6)/SO(5) $ coset structure and extract the scalar divergences to one loop. Assuming the additional scalar to be heavy, we integrate it out and perform a matching to the well-established electroweak chiral Lagrangian with one light Higgs.
We study the Leptogenesis and Dark Matter in the presence of an extra singlet complex scalar field in an extended discrete $\mathcal{Z_{\rm 3}}$ symmetry. The vacuum expectation value of the new scalar spontaneously breaks the $\mathcal{Z_{\rm 3}}$ symmetry. A remnant CP-like $\mathcal{Z_{\rm 2}}$ symmetry stabilizes the imaginary part of the complex scalar field which can act as a pseudo-Goldstone DM. The real part of the complex scalar couples to RHN opens up new decay channels which can lead to a larger CP-violation in generating the lepton asymmetry. Thus the singlet complex scalar plays a…
We study an extension of the scotogenic model with a real singlet scalar. It gives an origin of the mass of right-handed neutrinos and plays a role of inflaton through a non-minimal coupling with Ricci scalar. While an inert doublet scalar is an indispensable ingredient for neutrino mass generation in the model, it is also a promising dark matter (DM) candidate. Introduction of the singlet scalar could affect its nature of DM if mass of the singlet scalar is in a resonance region. We focus our study on such a case where inflaton mass is expected to be in a TeV range and reheating temperature i…
We explore a simple model containing two singlet scalars as dark matter supplemented with a vector-like lepton. Evading collider and dark matter constraints, the model is able to accommodate the correct dark matter relic abundance and the muon g-2 anomaly when the masses of the three new fields are around 100 GeV and the values of the minimum amount of required couplings are order one.
We study the simplest viable dark matter (DM) model with a real singlet scalar, vector-like singlet, and doublet fermions. The Yukawa couplings associated with the fermion sector are important in obtaining the current DM relic density through Freeze-out and Freeze-in mechanisms. In addition to the standard model-like high scale minima along the Higgs field, we find other high scale minima along the singlet scalar field direction. The other minima appears due to the renormalisation group evolutions of the couplings involving the gauge sector, Higgs portal, and the new Yukawa sector. A detailed …
We study a scalar singlet dark matter (DM) having mass in sub-TeV regime by extending the minimal scalar singlet DM setup by additional vector like fermions. While the minimal scalar singlet DM satisfies the relic and direct detection constraints for mass beyond TeV only, presence of its portal coupling with vector like fermions opens up additional co-annihilation channels. These vector like fermions also help in achieving electroweak vacuum stability all the way up to Planck scale. We find that for one generation of vector like quarks consisting of a $SU(2)_L$ doublet and a singlet, scalar si…
The leading order production of an SM singlet-like scalar has primarily been realized through the gluon fusion process by mixing with the $SU(2)_L$ scalar doublet of the model. The dominant part of the physical state, i.e., the singlet component, does not have any role in its direct production. Focusing on such a state with a mass smaller than the SM-like Higgs scalar, we calculate the dominant next-to-leading (NLO) order corrections to its production cross-section. With these improved cross-sections, the present and future LHC limits may become somewhat more stringent.
We consider the generation of neutrino masses via a singly-charged scalar singlet. Under general assumptions we identify two distinct structures for the neutrino mass matrix. This yields a constraint for the antisymmetric Yukawa coupling of the singly-charged scalar singlet to two left-handed lepton doublets, irrespective of how the breaking of lepton-number conservation is achieved. The constraint disfavours large hierarchies among the Yukawa couplings. We study the implications for the phenomenology of lepton-flavour universality, measurements of the $W$-boson mass, flavour violation in the …
We assume a generic real singlet scalar extension of the Standard Model living in the vacuum $(v,w)$ at the electroweak scale with $v=246$ GeV and $w$ being respectively the Higgs and the singlet scalar vacuum expectation values. By requiring {\it absolute} vacuum stability for the vacuum $(v,w)$, the positivity condition and the perturbativity up to the Planck scale, we show that the viable space of parameters in the model is strongly constrained for various singlet scalar vacuum expectation values $w=0.1, 1, 10, 100$ TeV. Also, it turns out that the singlet scalar mass can be from a few GeV …
We study the one-loop corrections to the $Zb\bar{b}$ vertex in extensions of the Standard Model with arbitrary numbers of scalar doublets, neutral scalar singlets, and charged scalar singlets. Starting with a general parameterization of theories with neutral and singly-charged scalar particles, we derive the conditions that, in a renormalizable model, must be obeyed by the couplings in order for the divergent contributions to cancel. Then, we show that those conditions are indeed obeyed by the models that we are interested in, and we write down the full finite expression for the vertex in thos…
We consider the unparticle physics introduced by Georgi and show that if the standard model is extended to include a singlet scalar as a dark matter candidate, there is a channel which leads to its decay to photon and unparticle. We calculate the decay rate for this new channel and find a lower bound on unparticle physics scale by demanding the stability of this candidate of the dark matter.
