arXiv subjects

Ana Martín-Galán

Publications and source records attributed to Ana Martín-Galán.

4 recordsLinked to original sources

arXiv2026

Flavorful Lepton-Number-Violating SMEFT: Loop Mixing, $0νββ$ and Rare Meson Decays

We investigate how one-loop operator mixing reshapes the flavor sensitivity of lepton-number-violating dimension-7 SMEFT interactions. Using both bottom-up and top-down EFT approaches, we study the interplay of neutrinoless double beta decay ($0νββ$) and neutral current rare meson decays $K\toπνν$, and $B\to K^{(*)}νν$, which at tree level probe apparently disconnected quark- and lepton-flavor sectors. We show that loop mixing qualitatively changes this picture: flavor structures radiatively feed into one another, substantially extending the sensitivity to higher new-physics scales across operators and flavors. In the bottom-up EFT approach, this can make $0νββ$ highly sensitive even to operators involving heavier-generation quarks, while rare kaon and $B$ decays retain crucial complementary sensitivity to other flavor combinations. A top-down EFT approach example using a ultraviolet model involving scalar-leptoquark illustrates how the same effects can reorder the relative importance of different observables.

hep-ph↗

arXiv2026

Searches for heavy neutral lepton decays at spallation neutron sources

Spallation neutron sources provide intense neutrino fluxes from pion and muon decay at rest, with energies in the few tens of MeV range. Experiments such as COHERENT exploit these fluxes to detect neutrinos via coherent elastic neutrino$\unicode{x2013}$nucleus scattering (CE$ν$NS). However, these facilities also offer a unique opportunity to produce and probe light, secluded, or weakly$\unicode{x2013}$coupled particles. In this work, we investigate the sensitivity of the Spallation Neutron Source at the Oak Ridge National Laboratory to heavy neutral leptons (HNLs) in the MeV$\unicode{x2013}$GeV mass range, as a case study. We consider HNL production in pion and muon decays at rest, followed by their decay into visible Standard Model particles within the detector volume. We analyze a range of current and proposed COHERENT detectors and evaluate their sensitivity to HNL mixing with muon and electron neutrinos, as well as to scenarios with mixed mixing. We find that existing detectors can set meaningful constraints, particularly for muon$\unicode{x2013}$flavor mixing, while future ton$\unicode{x2013}$scale realizations can probe previously unexplored regions of the parameter space. We further discuss prospects at other relevant spallation source facilities and comment on the complementarity of their projected sensitivities. Our results demonstrate that CE$ν$NS experiments at spallation neutron sources provide a powerful, complementary avenue for new physics searches beyond their primary role as neutrino detectors.

hep-ph↗

arXiv2026

Long-Lived HNLs via ALP Portal at the LHC

Heavy neutral leptons (HNLs) and axion-like particles (ALPs) are both considered well-motivated candidates for beyond the standard model (BSM) physics. If ALPs with sizable couplings to gluons exist, they will be abundantly produced at the LHC. Therefore, HNLs produced via the ALP portal may provide unprecedented sensitivities to HNL parameters. Here, we study the prospects for the high-luminosity LHC to search for long-lived HNLs. We consider future far detectors as well as ATLAS in our simulations. In the limit where the ALP mass is above the TeV scale, HNLs are effectively produced by a dimension-8 operator connecting HNL pairs to gluons. For completeness, we therefore also calculate future LHC sensitivities for HNLs produced via $N_R$SMEFT operators with gluons.

hep-ph↗

arXiv2025

Importance of Loop Effects in Probing Lepton Number Violation

The discovery of the lepton number violation would be a smoking gun signal for physics beyond the Standard Model, and its most sensitive probe is the search for neutrinoless double beta decay ($0νββ$). Working in the framework of the Standard Model Effective Field Theory (SMEFT), we show that one-loop effects can remarkably improve the tree-level bounds on the new-physics scales for several dimension-7 operators. Using ultraviolet model examples, we then showcase the competition among $0νββ$ contributions induced by dimension-7 and loop-level dimension-5 SMEFT operators.

hep-ph↗