arXiv subjects

Luighi P. S. Leal

Publications and source records attributed to Luighi P. S. Leal.

4 recordsLinked to original sources

arXiv2026

Challenging Majorana neutrino effects in $B\to K^{(\ast)}νν$ and $K\to πνν$ decays

We investigate the contributions of Lepton Number Violating (LNV) effective operators to the rare decays $B\to K^{(\ast)}νν$ and $K\to πνν$. Such operators can modify the kinematic distributions of these processes, providing distinctive probes of physics beyond the Standard Model. Through a renormalization-group analysis, we show that the Standard Model Effective Field Theory (SMEFT) operators responsible for these effects are subject to stringent indirect constraints from neutrino physics. In particular, we find that the mild excess reported by Belle-II in the $B^+\to K^+νν$ channel cannot be explained by LNV SMEFT operators without introducing significant fine-tuning in neutrino masses. We then show that these constraints can be evaded in the SMEFT minimally extended by a light right-handed neutrino, allowing for sizable effects in rare meson decays. Finally, we explore the implications of this viable scenario for low-energy processes, including neutrinoless double-beta decays.

hep-ph↗

arXiv2025

Cosmogenic neutrinos as probes of new physics

The scattering of extremely energetic cosmic rays with both cosmic microwave background and extragalactic background light, can produce $\mathcal{O}(10^{18} \,{\rm eV})$ neutrinos, known as cosmogenic neutrinos. These neutrinos are the only messengers from the extreme cosmic accelerators that can reveal the origin of the most energetic cosmic rays. Consequently, much effort is being devoted to achieving their detection. In particular, the GRAND project aims to observe the $ν_τ$ and $\bar ν_τ$ components of the cosmogenic neutrino flux in the near future using radio antennas. In this work, we investigate how the detection of cosmogenic neutrinos by GRAND can be used to probe beyond the Standard Model physics. We identify three well-motivated scenarios which induce distinct features in the cosmogenic neutrino spectrum at Earth: neutrino self-interactions mediated by a light scalar ($ν$SI), pseudo-Dirac neutrinos (PD$ν$) and neutrinos scattering on ultra-light Dark Matter ($ν$DM). We show these scenarios can be tested by GRAND, using 10 years of cosmogenic neutrino data, in a region of parameter space complementary to current experiments. For the $ν$SI model,, we find that GRAND can constrain the coupling to $ν_τ$ in the range [$10^{-2},10^{-1}$] for a scalar with mass in the range 0.1 to 1 GeV. For PD$ν$, we find that GRAND is sensitive to sterile-active mass squared splitting in the range [$10^{-15},10^{-13}$] ${\rm eV}^2$. Finally, for the $ν$DM model, assuming a heavy mediator, GRAND can do substantially better than the current limits from other available data. These results rely on the fact that the actual cosmogenic flux is around the corner, not far from the current IceCube limit.

hep-ph↗

arXiv2023

New limits on $W_R$ from meson decays

In this letter we show that pseudoscalar meson leptonic decay data can be used to set stringent limits on the mass $m_{W_R}$ of a right-handed vector boson, such as the one that appears in left-right symmetric models. We have shown that for a heavy neutrino with a mass $m_N$ in the range $50<m_N/{\rm MeV} <1900$ one can constraint $m_{W_R} \lesssim (4-19)$ TeV at 90 % CL. This provides the most stringent experimental limits on the $W_R$ mass to date.

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arXiv2022

Exploring the Neutrino Sector of the Minimal Left-Right Symmetric Model

We explore the neutrino sector of the minimal left-right symmetric model, with the additional charge conjugation discrete symmetry, in the tuned regime where type-I and type-II seesaw mechanisms are equally responsible for the light neutrino masses. We show that unless the charged lepton mixing matrix is the identity and the right handed neutrino mass matrix has no phases, we expect sizable lepton flavor violation and electron dipole moment in this region. We use results from recent neutrino oscillation fits, bounds on neutrinoless double beta decay, $μ\to e γ$, $μ\to 3 e$, $μ\to e$ conversion in nuclei, the muon anomalous magnetic moment, the electron electric dipole moment and cosmology to determine the viability of this region. We derive stringent limits on the heavy neutrino masses and mixing angles as well as on the vacuum expectation value $v_L$, which drives the type-II seesaw contribution, using the current data. We discuss the perspectives of probing the remaining parameter space by future experiments.

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