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1. Neutrino mass from Affleck-Dine leptogenesis and WIMP dark matte

   https://doi.org/https://doi.org/10.1007/JHEP03(2022)092  

   Rabindra N. Mohapatra and Nobuchika Okada (March 2022, The Journal of high energy physics)

   Affleck-Dine (AD) mechanism for leptogenesis involves the cosmological evolution of a complex scalar field (AD field) that carries non-zero lepton number. We show how explicit lepton number breaking terms, which involve the AD field needed to implement this scenario combined with fermionic WIMP dark matter, can generate neutrino mass at the one loop level, thus providing a unified framework for solving four major puzzles of the standard model i.e. inflation, baryogenesis, dark matter and neutrino mass. We discuss some phenomenological implications of this model. 

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2. 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. 

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3. TwInflation

   https://doi.org/10.1007/JHEP07(2021)147  

   Deshpande, Kaustubh; Kumar, Soubhik; Sundrum, Raman (July 2021, Journal of High Energy Physics)

   null (Ed.)

   A bstract The general structure of Hybrid Inflation remains a very well-motivated mechanism for lower-scale cosmic inflation in the face of improving constraints on the tensor-to-scalar ratio. However, as originally modeled, the “waterfall” field in this mechanism gives rise to a hierarchy problem ( η− problem) for the inflaton after demanding standard effective field theory (EFT) control. We modify the hybrid mechanism and incorporate a discrete “twin” symmetry, thereby yielding a viable, natural and EFT-controlled model of non-supersymmetric low-scale inflation, “Twinflation”. Analogously to Twin Higgs models, the discrete exchange-symmetry with a “twin” sector reduces quadratic sensitivity in the inflationary potential to ultra-violet physics, at the root of the hierarchy problem. The observed phase of inflation takes place on a hilltop-like potential but without fine-tuning of the initial inflaton position in field-space. We also show that all parameters of the model can take natural values, below any associated EFT-cutoff mass scales and field values, thus ensuring straightforward theoretical control. We discuss the basic phenomenological considerations and constraints, as well as possible future directions. 

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4. Sterile neutrino dark matter and leptogenesis in Left-Right Higgs Parity

   https://doi.org/10.1007/JHEP01(2021)125  

   Dunsky, David; Hall, Lawrence J.; Harigaya, Keisuke (January 2021, Journal of High Energy Physics)

   A bstract The standard model Higgs quartic coupling vanishes at (10 9 − 10 13 ) GeV. We study SU(2) L × SU(2) R × U(1) B−L theories that incorporate the Higgs Parity mechanism, where this becomes the scale of Left-Right symmetry breaking, v R . Furthermore, these theories solve the strong CP problem and predict three right-handed neutrinos. We introduce cosmologies where SU(2) R × U(1) B−L gauge interactions produce right-handed neutrinos via the freeze-out or freeze-in mechanisms. In both cases, we find the parameter space where the lightest right-handed neutrino is dark matter and the decay of a heavier one creates the baryon asymmetry of the universe via leptogenesis. A theory of flavor is constructed that naturally accounts for the lightness and stability of the right-handed neutrino dark matter, while maintaining sufficient baryon asymmetry. The dark matter abundance and successful natural leptogenesis require v R to be in the range (10 10 − 10 13 ) GeV for freeze-out, in remarkable agreement with the scale where the Higgs quartic coupling vanishes, whereas freeze-in requires v R ≳ 10 9 GeV. The allowed parameter space can be probed by the warmness of dark matter, precise determinations of the top quark mass and QCD coupling by future colliders and lattice computations, and measurement of the neutrino mass hierarchy. 

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5. Search for resonant and non-resonant Higgs boson pair production in the $$ b\overline{b}{\tau}^{+}{\tau}^{-} $$ decay channel using 13 TeV pp collision data from the ATLAS detector

   https://doi.org/10.1007/JHEP07(2023)040  

   Aad, G.; Abbott, B.; Abbott, D. C.; Abed Abud, A.; Abeling, K.; Abhayasinghe, D. K.; Abidi, S. H.; Aboulhorma, A.; Abramowicz, H.; Abreu, H.; et al (July 2023, Journal of High Energy Physics)

   A bstract A search for Higgs boson pair production in events with two b -jets and two τ -leptons is presented, using a proton–proton collision dataset with an integrated luminosity of 139 fb − 1 collected at $$ \sqrt{s} $$ s = 13 TeV by the ATLAS experiment at the LHC. Higgs boson pairs produced non-resonantly or in the decay of a narrow scalar resonance in the mass range from 251 to 1600 GeV are targeted. Events in which at least one τ -lepton decays hadronically are considered, and multivariate discriminants are used to reject the backgrounds. No significant excess of events above the expected background is observed in the non-resonant search. The largest excess in the resonant search is observed at a resonance mass of 1 TeV, with a local (global) significance of 3 . 1 σ (2 . 0 σ ). Observed (expected) 95% confidence-level upper limits are set on the non-resonant Higgs boson pair-production cross-section at 4.7 (3.9) times the Standard Model prediction, assuming Standard Model kinematics, and on the resonant Higgs boson pair-production cross-section at between 21 and 900 fb (12 and 840 fb), depending on the mass of the narrow scalar resonance. 

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