Search

We explore the possibility of resolving the Hubble tension and |$(g-2)_{\mu}$| anomaly simultaneously in a U(1) |$_{L_\mu - L_\tau}$| model with Majoron. We only focus on the case where the Majoron |$\phi$| does not exist at the beginning of the universe and is created by neutrino inverse decay |$\nu\nu\to \phi$| after electron–positron annihilation. In this case, the contributions of the new gauge boson |$Z'$| and the Majoron |$\phi$| to the effective number of neutrino species |$N_{\rm eff}$| can be calculated in separate periods. These contributions are labelled |$N'_{\rm eff}$| for the U(1) |$_{L_\mu - L_\tau}$| gauge boson and |$\Delta N_{\rm eff}^\prime$| for the Majoron. The effective number |$N_{\rm eff} = N'_{\rm eff} + \Delta N_{\rm eff}^\prime$| is evaluated by the evolution equations of the temperatures and the chemical potentials of light particles in each period. As a result, we find that the heavier |$Z'$| mass |$m_{Z^\prime}$| results in a smaller |$N_{\mathrm{eff}}^\prime$| and requires a larger |$\Delta N_{\mathrm{eff}}^\prime$| to resolve the Hubble tension. Therefore, compared to previous studies, the parameter region where the Hubble tension can be resolved is slightly shifted toward the larger value of |$m_{Z^\prime}$|⁠. [ABSTRACT FROM AUTHOR]

Abstract We propose a new interpretation of Peccei–Quinn symmetry within the Standard Model, identifying it with the axial B + L symmetry i.e. U (1) P Q ≡ U (1) γ 5 (B + L). This new interpretation retains all the attractive features of Peccei–Quinn solution to strong CP problem but in addition also leads to several other new and interesting consequences. Owing to the identification U (1) P Q ≡ U (1) γ 5 (B + L) the axion also behaves like Majoron inducing small seesaw masses for neutrinos after spontaneous symmetry breaking. Another novel feature of this identification is the phenomenon of spontaneous (and also chiral) proton decay with its decay rate associated with the axion decay constant. Low energy processes which can be used to test this interpretation are pointed out. [ABSTRACT FROM AUTHOR]

Abstract Searches for neutrino-less double-beta decay (0 ν 2 β) place an important constraint on models where light fields beyond the Standard Model participate in the neutrino mass mechanism. While 0 ν 2 β experimental collaborations often consider various massless majoron models, including various forms of majoron couplings and multi-majoron final-state processes, none of these searches considered the scenario where the "majoron" ϕ is not massless, m ϕ ∼ MeV, of the same order as the Q -value of the 0 ν 2 β reaction. We consider this parameter region and estimate 0 ν 2 β ϕ constraints for m ϕ of order MeV. The constraints are affected not only by kinematical phase space suppression but also by a change in the signal to background ratio charachterizing the search. As a result, 0 ν 2 β ϕ constraints for m ϕ > 0 diminish significantly below the reaction threshold. This has phenomenological implications, which we illustrate focusing on high-energy neutrino telescopes. The spectral shape of high-energy astrophysical neutrinos could exhibit features due to resonant ν ν → ϕ → ν ν scattering. Such features fall within the sensitivity range of IceCube-like experiments, if m ϕ is of order MeV, making 0 ν 2 β ϕ a key complimentary laboratory constraint on the scenario. Our results motivate a dedicated analysis by 0 ν 2 β collaborations, analogous to the dedicated analyses targeting massless majoron models. [ABSTRACT FROM AUTHOR]

Models with spontaneously broken global lepton number can lead to a pseudo-Goldstone boson as a long-lived dark matter candidate. Here we revisit the case of singlet majoron dark matter and discuss multiple constraints. For masses above MeV, this model could lead to a detectable flux of monochromatic mass-eigenstate neutrinos, which have flavor ratios that depend strongly on the neutrino mass hierarchy. We provide a convenient parametrization for the loop-induced majoron couplings to charged fermions that allows us to discuss three-generation effects such as lepton flavor violation. These couplings are independent of the low-energy neutrino parameters but can be constrained by the majoron decays into charged fermions. [ABSTRACT FROM AUTHOR]

A complete calculation of phase space factors (PSFs) for Majoron-emitting 0νβ-β- decay modes is presented. The calculation makes use of exact Dirac wave functions with finite nuclear size and electron screening and includes lifetimes, single-electron spectra, summed electron spectra, and angular electron correlations. Combining these results with recent microscopic interacting boson model nuclear matrix elements (NMEs) we make half-life predictions for the ordinary Majoron decay (spectral index n=1). Furthermore, comparing theoretical predictions with the obtained experimental lower bounds for this decay mode we are able to set limits on the effective Majoron-neutrino coupling constant 〈gMee〉. [ABSTRACT FROM AUTHOR]

Abstract: The origin of dark matter and the generation of neutrino masses could be related if neutrino masses arise from the spontaneous violation of ungauged lepton number. In this case the associated Nambu–Goldstone boson, the majoron, could acquire a mass from non-perturbative gravitational effects and play the role of DM. Here we report our cosmological and astrophysical constraints on majoron dark matter coming from Cosmic Microwave Background (CMB) and a variety of X- and γ-ray observations. [Copyright &y& Elsevier]

Abstract: We discuss some phenomenological consequences in a scenario where a singlet Majoron plays the role of dark radiation. We study the interrelations between neutrino mass generation and the scalar potential arising from this identification. We find the extra scalar has to be light with a mass at or below the GeV level. The mixing of this scalar with the Standard Model Higgs impacts low energy phenomena such as the muonic hydrogen Lamb shift and muon anomalous magnetic moment. Demanding that the light scalar solves the puzzle in the muon magnetic moment requires the scalar to be lighter still with mass at or below the 10 MeV level. The cross-sections for the production of heavy neutrinos at LHC14 are also given. [Copyright &y& Elsevier]

In the projected-Hartree-Fock-Bogoliubov (PHFB) model, uncertainties in the nuclear transition matrix elements for the neutrinoless double-β decay of 94,96Zr, 98,100Mo, 104Ru, 110Pd, 128,l30Te, and 150Nd isotopes within mechanisms involving light Majorana neutrinos, classical Majorons, and sterile neutrinos are statistically estimated by considering sets of 16 (24) matrix elements calculated with four different parametrizations of the pairing plus multipolar type of effective two-body interaction, two sets of form factors, and two (three) different parametrizations of Jastrow type of short-range correlations. In the mechanisms involving the light Majorana neutrinos and classical Majorons, the maximum uncertainty is about 15% and in the scenario of sterile neutrinos, it varies in between approximately 4 (9)%-20 (36)% without(with) Jastrow short range correlations with the Miller-Spencer parametrization, depending on the considered mass of the sterile neutrinos. [ABSTRACT FROM AUTHOR]

We compute the effective coupling of the Majoron to W bosons at $\mathcal{O}(\hbar)$ by evaluating the matrix element of the ( B- L) current between the vacuum and a W W state. The ( B- L) anomaly vanishes, but the amplitude does not vanish as a result of a UV finite and non-local contribution which is entirely due to the mixing between left-chiral and right-chiral neutrinos. The result shows how anomaly-like couplings may arise in spite of the fact that the ( B- L) current remains exactly conserved to all orders in ħ, lending additional support to our previous proposal to identify the Majoron with the axion. [ABSTRACT FROM AUTHOR]

In the singlet Majoron model, we study cosmological phase transitions (PTs) and their resulting gravitational waves (GWs), in the two-field phase space, without freezing any of the field directions. We first calculate the effective potential, at one loop and at finite temperature, of the Standard Model Higgs doublet together with one extra Higgs singlet. We make use of the public available Python package 'CosmoTransitions' to simulate the two-dimensional (2D) cosmological PTs and evaluate the gravitational waves generated by first-order PTs. With the full 2D simulation, we are able not only to confirm the PTs' properties previously discussed in the literature, but also we find new patterns, such as strong first-order PTs tunneling from a vacuum located on one axis to another vacuum located on the second axis. The two-field phase space analysis presents a richer panel of cosmological PT patterns compared to analysis with a single-field approximation. The PTGW amplitudes turn out to be out of the reach for the space-borne gravitational wave interferometers such as LISA, DECIGO, BBO, TAIJI and TianQin when constraints from colliders physics are taken into account. [ABSTRACT FROM AUTHOR]

A correction to the article "Phase-space factors and half-life predictions for Majoron-emitting β238β238 decay" that was published in the August 31, 2015 issue is presented.

The origin of neutrino masses and the nature of dark matter are two in most pressing open questions in modern astro-particle physics. We consider here the possibility that these two problems are related, and review some theoretical scenarios which offer common solutions. A simple possibility is that the dark matter particle emerges in minimal realizations of the seesaw mechanism, as in the majoron and sterile neutrino scenarios. We present the theoretical motivation for both models and discuss their phenomenology, confronting the predictions of these scenarios with cosmological and astrophysical observations. Finally, we discuss the possibility that the stability of dark matter originates from a flavor symmetry of the leptonic sector. We review a proposal based on an A4 flavor symmetry. [ABSTRACT FROM AUTHOR]