More Like this

1. Unified model for inflation, pseudo-Goldstone dark matter, neutrino mass, and baryogenesis

   https://doi.org/https://doi.org/10.1103/PhysRevD.105.035024  

   Rabindra N. Mohapatra and Nobuchika Okada (February 2022, Physical Review)

   We present a unified theory of inflation, neutrino mass, baryogenesis, and dark matter where global lepton number symmetry and its breaking play a crucial role. The basic idea is to use a lepton number carrying a complex scalar field as the inflaton as well as the field that implements Affleck-Dine (AD) leptogenesis. Dark matter is the massive Majoron which is a pseudo-Goldstone boson, resulting from the spontaneous breaking of lepton number symmetry supplemented by explicit lepton number violation needed to implement AD leptogenesis. The magnitude of the resulting nB/s in the model is related to the mass of the pseudo-Goldstone dark matter, connecting two apparently disconnected cosmological observations. An inverse seesaw mechanism with lepton number breaking at low scale is crucial to prevent washout of the lepton asymmetry during the universe’s evolution. The model seems to provide an economical solution to several puzzles of the standard model of particle physics and cosmology in one stroke. 

   more » « less
2. Neutrinos in Astrophysics and Cosmology

   https://doi.org/10.22323/1.388.0001  

   Abazajian, Kevork (September 2021, Theoretical Advanced Study Institute (TASI) 2020)

   I introduce the consequences of neutrino mass and mixing in the dense environments of the early Universe and in astrophysical environments. Thermal and matter effects are reviewed in the context of a two-neutrino formalism, with methods of extension to multiple neutrinos. The observed large neutrino mixing angles place the strongest constraint on cosmological lepton (or neutrino) asymmetries, while new sterile neutrinos provide a wealth of possible new physics, including lepton asymmetry generation as well as candidates for dark matter. I also review cosmic microwave background and large-scale structure constraints on neutrino mass and energy density. Lastly, I review how X-ray astronomy has become a branch of neutrino physics in searches for keV-scale sterile neutrino dark matter radiative decay. 

   more » « less
3. Interplay of freeze-in and freeze-out: Lepton-flavored dark matter and muon colliders

   https://doi.org/10.1103/PhysRevD.110.035022  

   Asadi, Pouya; Radick, Aria; Yu, Tien-Tien (August 2024, Physical Review D)

   We study a lepton-flavored dark matter model and its signatures at a future muon collider. We focus on the less-explored regime of feeble dark matter interactions, which suppresses the dangerous lepton-flavor-violating processes, gives rise to dark matter freeze-in production, and leads to long-lived particle signatures at colliders. We find that the interplay of dark matter freeze-in and its mediator freeze-out gives rise to an upper bound of around TeV scales on the dark matter mass. The signatures of this model depend on the lifetime of the mediator and can range from generic prompt decays to more exotic long-lived particle signals. In the prompt region, we calculate the signal yield, study useful kinematics cuts, and report tolerable systematics that would allow for a $5\sigma$discovery. In the long-lived region, we calculate the number of charged tracks and displaced lepton signals of our model in different parts of the detector and uncover kinematic features that can be used for background rejection. We show that, unlike in hadron colliders, multiple production channels contribute significantly, which leads to sharply distinct kinematics for electroweakly charged long-lived particle signals. Ultimately, the collider signatures of this lepton-flavored dark matter model are common among models of electroweak-charged new physics, rendering this model a useful and broadly applicable benchmark model for future muon collider studies that can help inform work on detector design and studies of systematics. Published by the American Physical Society2024 

   more » « less
4. Lepto-axiogenesis

   https://doi.org/10.1007/JHEP03(2021)017  

   Co, Raymond T.; Fernandez, Nicolas; Ghalsasi, Akshay; Hall, Lawrence J.; Harigaya, Keisuke (March 2021, Journal of High Energy Physics)

   A bstract We propose a baryogenenesis mechanism that uses a rotating condensate of a Peccei-Quinn (PQ) symmetry breaking field and the dimension-five operator that gives Majorana neutrino masses. The rotation induces charge asymmetries for the Higgs boson and for lepton chirality through sphaleron processes and Yukawa interactions. The dimension-five interaction transfers these asymmetries to the lepton asymmetry, which in turn is transferred into the baryon asymmetry through the electroweak sphaleron process. QCD axion dark matter can be simultaneously produced by dynamics of the same PQ field via kinetic misalignment or parametric resonance, favoring an axion decay constant f a ≲ 10 10 GeV, or by conventional misalignment and contributions from strings and domain walls with f a ∼ 10 11 GeV. The size of the baryon asymmetry is tied to the mass of the PQ field. In simple supersymmetric theories, it is independent of UV parameters and predicts the supersymmtry breaking mass scale to be $$ \mathcal{O} $$ O (10 − 10 4 ) TeV, depending on the masses of the neutrinos and whether the condensate is thermalized during a radiation or matter dominated era. The high supersymmetry breaking mass scale may be free from cosmological and flavor/CP problems. We also construct a theory where TeV scale supersymmetry is possible. Parametric resonance may give warm axions, and the radial component of the PQ field may give signals in rare kaon decays from mixing with the Higgs and in dark radiation. 

   more » « less
5. Neutrino masses and mixing in models with large extra dimensions and localized fermions

   https://doi.org/https://doi.org/10.1103/PhysRevD.103.015021  

   Girmohanta, S. (January 2021, Physical review)

   Using a low-energy effective field theory approach, we study some properties of models with large extra dimensions, in which quarks and leptons have localized wave functions in the extra dimensions. We consider models with two types of gauge groups: (i) the Standard-Model gauge group, and (ii) the left-right symmetric gauge group. Our main focus is on the lepton sector of models with n=2 extra dimensions, in particular, neutrino masses and mixing. We analyze the requisite conditions that the models must satisfy to be in accord with data and present a solution for lepton wave functions in the extra dimensions that fulfils these conditions. As part of our work, we also present a new solution for quark wave function centers. Issues with flavor-changing neutral-current effects are assessed. Finally, we remark on baryogenesis and dark matter in these models. 

   more » « less