arXiv subjects

S. Marciano

Publications and source records attributed to S. Marciano.

2 recordsLinked to original sources

arXiv2025

A Roadmap for neutrino charge assignments in $U(2)_F$ Flavor Models: Implications for LFV processes and leptonic anomalous magnetic moments

We build upon a simple $U(2)_F$ model of flavor, in which all fermion masses and mixing hierarchies arise from powers of two small parameters controlling $U(2)_F$ breaking. In the original formulation, an isomorphism to the discrete $D_6\times U(1)_F$ symmetry was invoked to generate a Majorana neutrino mass term. Here, we retain the successful features of that model for the charged leptons and quarks, while exploring alternative neutrino charge assignments within the $U(2)_F$ framework. This approach allows us to generate Majorana neutrino masses via the see-saw mechanism without introducing any additional symmetries nor invoking any isomorphism. We further examine the implications of our models for Lepton Flavor Violating (LFV) decays, analyzing the processes $\mu\rightarrow e\gamma$, $\tau\rightarrow\mu\gamma$ and $\tau\rightarrow e\gamma$ and their connection with the leptonic anomalous magnetic moments. We show that within the Standard Model Effective Field Theory (SMEFT) approach the current limits on the branching ratios of $\mu\rightarrow e\gamma$ LFV decays obtained in our $U(2)_F$ models are not compatible with the central value of the recent measurement of the $(g-2)_\mu$, thereby suggesting that either $(g-2)_\mu$ must be very close to the Standard Model predictions, as the latest experimental and theoretical results seem to suggest, or the invoked flavor symmetry is not appropriate to describe an anomalous muon magnetic moment.

hep-ph↗

arXiv2025

Probing Long-Range Forces in Neutrino Oscillations at the ESSnuSB Experiment

Neutrino oscillations constitute an excellent tool to probe physics beyond the Standard Model. In this paper, we investigate the potential of the ESSnuSB experiment to constrain the effects of flavour-dependent long-range forces (LRFs) in neutrino oscillations, which may arise due to the extension of the Standard Model gauge group by introducing new $U(1)$ symmetries. Focusing on three specific $U(1)$ symmetries -- $L_e - L_\mu$, $L_e - L_\tau$, and $L_\mu - L_\tau$, we demonstrate that ESSnuSB offers a favourable environment to search for LRF effects. Our analyses reveal that ESSnuSB can set $90\%$ confidence level bounds of $V_{e\mu} < 2.99 \times 10^{-14} \, \text{eV}$, $V_{e\tau} < 2.05 \times 10^{-14} \, \text{eV}$, and $V_{\mu\tau} < 1.81 \times 10^{-14} \, \text{eV}$, which are competitive to the upcoming Deep Underground Neutrino Experiment (DUNE). It is also observed that reducing the systematic uncertainties from $5\%$ to $2\%$ improves the ESSnuSB limits on $V_{\alpha\beta}$. Interestingly, we find limited correlations between LRF parameters and the less constrained lepton mixing parameters $\theta_{23}$ and $\delta_{\text{CP}}$, preserving the robustness of ESSnuSB's sensitivity to CP violation. Even under extreme LRF potentials ($V_{\alpha\beta} \gg 10^{-13} \, \text{eV}$), the CP-violation sensitivity and $\delta_{\text{CP}}$ precision remain largely unaffected. These results establish ESSnuSB as a competitive experimental setup for probing LRF effects, complementing constraints from other neutrino sources and offering critical insights into the physics of long-range forces.

hep-ph↗