arXiv subjects
Publications and source records attributed to Alexander Natale.
Dark pion is the one of the most natural and realistic model to make $3 \rightarrow 2$ contact interactions among models of the Strongly Interacting Massive Particle (SIMP). In this model, there is a perturbativity problem to satisfy the relic density with the self-annihilation. So we show the perturbativity problem can be alleviated and the SIMP pion model become more realistic by including dark vector mesons.
We consider a light dark matter candidate which is produced by the freeze-out mechanism with $3\rightarrow2$ annihilations, the so called Strongly Interacting Massive Particles (SIMPs). SIMPs are identified as dark pions in dark chiral perturbation theory (ChPT) where both light mass and strong coupling needed for SIMPs can be realized by strong dynamics. In QCD-like theories with $SU(3)_L \times SU(3)_R /SU(3)_V$ flavor symmetry, including dark vector mesons in the hidden local symmetry scheme, we illustrate that dark vector mesons unitarize the dark ChPT efficiently, thus determine the correct relic density condition within the validity of the dark ChPT.
A radiative model of quark and lepton masses utilizing the binary tetrahedral ($T^{\prime}$) flavor symmetry, or horizontal symmetry, is proposed which produces the first two generation of quark masses through their interactions with vector-like quarks that carry charges under an additional $U(1)$. By softly-breaking the $T^{\prime}$ to a residual $Z_4$ through the vector-like quark masses, a CKM mixing angle close to the Cabibbo angle is produced. In order to generate the cobimaximal neutrino oscillation pattern ($θ_{13}\neq0,θ_{23}=π/4,δ_{CP}=\pm π/2$) and protect the horizontal symmetry from arbitrary corrections in the lepton sector, there are automatically two stabilizing symmetries in the dark sector. Several benchmark cases where the correct relic density is achieved in a multi-component DM scenario, as well as the potential collider signatures of the vector-like quarks are discussed.
The general strategy for dark matter (DM) searches at colliders currently relies on simplified models. In this paper, we propose a new $t$-channel UV-complete simplified model that improves the existing simplified DM models in two important respects: (i) we impose the full SM gauge symmetry including the fact that the left-handed and the right-handed fermions have two independent mediators with two independent couplings, and (ii) we include the renormalization group evolution when we derive the effective Lagrangian for DM-nucleon scattering from the underlying UV complete models by integrating out the $t$-channel mediators. The first improvement will introduce a few more new parameters compared with the existing simplified DM models. In this study we look at the effect this broader set of free parameters has on direct detection and the mono-$X$ + MET ($X$=jet,$W,Z$) signatures at 13 TeV LHC while maintaining gauge invariance of the simplified model under the full SM gauge group. We find that the direct detection constraints require DM masses less than 10 GeV in order to produce phenomenologically interesting collider signatures. Additionally, for a fixed mono-W cross section it is possible to see very large differences in the mono-jet cross section when the usual simplified model assumptions are loosened and isospin violation between RH and LH DM-SM quark couplings are allowed.
A special form of the $3 \times 3$ Majorana neutrino mass matrix derivable from $μ- τ$ interchange symmetry accompanied by a generalized $CP$ transformation was obtained many years ago. It predicts $θ_{23} = π/4$ as well as $δ_{CP} = \pm π/2$, with $θ_{13} \neq 0$. Whereas this is consistent with present data, we explore a deviation of this result which occurs naturally in a recent proposed model of radiative inverse seesaw neutrino mass.
The notion that dark matter and standard-model matter are connected through flavor implies a generic collider signature of the type 2 jets + $μ^\pm$ + $e^\mp$ + missing energy. We discuss the theoretical basis of this proposal and its verifiability at the Large Hadron Collider.
The scotogenic model of radiative neutrino mass with $Z_2$ or $U(1)_D$ dark matter is shown to accommodate $Δ(27)$ symmetry naturally. The resulting neutrino mass matrix is identical to either of two forms, one proposed in 2006, the other in 2008. These two structures are studied in the context of present neutrino data, with predictions of $CP$ violation and neutrinoless double beta decay.
A new idea for neutrino mass was proposed recently, where its smallness is not due to the seesaw mechanism, i.e. not inversely proportional to some large mass scale. It comes from a one-loop mechanism with dark matter in the loop consisting of singlet Majorana fermions $N_i$ with masses of order 10 keV and neutrino masses are scaled down from them by factors of about $10^{-5}$. We discuss how this model may be implemented with the non-Abelian discrete symmetry $A_4$ for neutrino mixing, and consider the phenomenology of $N_i$ as well as the extra scalar doublet $(η^+,η^0)$.
The non-Abelian discrete symmetry D(7) of the heptagon is successfully applied to both quark and lepton mass matrices, including CP violation.
Assuming that neutrinos acquire radiative seesaw Majorana masses through their interactions with dark matter, i.e. scotogenic from the Greek 'scotos' meaning darkness, and using the non-Abelian discrete symmetry $A_4$, we propose a model of neutrino masses and mixing with nonzero $θ_{13}$ and necessarily large leptonic CP violation, allowing both the normal and inverted hierarchies of neutrino masses, as well as quasi-degenerate solutions.