arXiv subjects

Juan Manuel Márquez

Publications and source records attributed to Juan Manuel Márquez.

5 recordsLinked to original sources

arXiv2025

Proton-box contribution to $a_μ^{\rm{HLbL}}$

We analyze the proton$\text{-}$box contribution to the hadronic light$\text{-}$by$\text{-}$light part of the muon's anomalous magnetic moment, which is the first reported baryonic contribution to this piece. We follow the quark$\text{-}$loop analysis, incorporating the relevant data$\text{-}$driven and lattice proton form factors. Although the heavy mass expansion would yield a contribution of $\mathcal{O}(10^{-10})$, the damping of the form factors in the regions where the kernel peaks, explains our finding $a_μ^{\rm{p-box}}=1.82 (7)\times 10^{-12}$, two orders of magnitude smaller than the forthcoming uncertainty on the $a_μ$ measurement and on its Standard Model prediction.

hep-ph↗

arXiv2025

HEFT approach to investigate the muon g-2 anomaly at a muon collider

In a previous work \cite{Buttazzo:2020ibd}, it has been pointed out that heavy new physics (NP) contributions to lepton dipole moments and high-energy cross-sections of lepton pairs into Higgs and $γ/Z$ bosons are connected, if the electroweak symmetry breaking is realized linearly. As a consequence, a multi-TeV muon collider would provide a unique test of NP in the muon $g$-2 through the study of high-energy processes such as $μ^+ μ^-\to h +γ/Z$. Since the analysis involved a SMEFT approach to Higgs-processes, it could also be studied by the more general HEFT formulation. We compute the modification of the high-energy cross-section $μ^+ μ^-\to h +γ/Z$ and $h\to μ^{+} μ^{-} +γ/Z$ decay using the dimension six HEFT Lagrangian and compare them with the SMEFT analysis. We find that, within the current HEFT analysis, there are plausible scenarios where the HEFT approach could lead to a higher sensitivity to test the NP contributions in the muon $g$-2. However, a more precise knowledge of the new HEFT parameters is needed for a definite conclusion, which motivates the search for complementary measurements.

hep-ph↗

arXiv2024

$νe\toνe$ scattering with massive Dirac or Majorana neutrinos and general interactions

We calculate the neutrino-electron elastic scattering cross section, extending the results previously obtained in arXiv:1702.05721v2, in the presence of generic new interactions that take into account all the effects caused by finite neutrino masses. We address the potential significance of a heavy neutrino sector during precision measurements, particularly for tau neutrinos scattering with masses in the MeV range, for which the existing upper bounds on $|U_{τ4}|^2$ would result in conceivably measurable contributions. Finally, we comment on the possibility to distinguish between Dirac and Majorana neutrinos, including the analysis of the new emerging parameters and its application to illustrative model-dependent scenarios.

hep-ph↗

arXiv2024

Dirac-Majorana neutrinos distinction in four-body decays

A novel method to differentiate the effects of Dirac and Majorana (D-M) neutrinos in four-body decays has been discussed in arXiv:2106.11785. There, it is concluded that the back-to-back kinematic scenario seems to avoid the constraint imposed by the "practical Dirac-Majorana confusion theorem", as one does not need to fully integrate over neutrino and antineutrino momenta. In this paper, we propose to analyse radiative leptonic lepton-decays ($\ell\to\ell'ν\barνγ$), as an independent alternative process to study the possible Majorana nature of neutrinos. Our approach demonstrates that, in the back-to-back kinematic configuration (for the $\ell'- γ$ and $ν-\barν$ systems, respectively), the distinction between Dirac and Majorana cases disappears when the inaccessible neutrino angle is integrated out, which might appear unexpected considering the claims in arXiv:2106.11785. Our results apply in absence of non-standard interactions, which can enhance generally the sensitivity to the neutrino nature.

hep-ph↗

arXiv2023

Michel parameters in the presence of massive Dirac and Majorana neutrinos

We analyse the effects of Dirac and Majorana neutrinos on leptonic decays of muon and tau leptons using the most general four-lepton effective interaction Hamiltonian of dimension six. We calculate the specific energy and angular distribution of the final charged lepton, including the polarizations of the initial and final charged leptons. We discuss the new generalized Michel parameters and focus on the effects of the heavy neutrino masses that would lead to sizable contributions on scenarios where the new sterile neutrinos have non-negligible mixing. Specifically, the most promising scenario is found for the case of $τ$ decay with one heavy final-state neutrino with a mass around $10^2 - 10^3$ MeV, where the linear term suppression could be of order $10^{-4}$, low enough to be measured in current and forthcoming experiments.

hep-ph↗