Leptoquark-mediated Dirac neutrino mass and its impact on $B \to K ν\barν$ and $K \to πν\barν$ decays
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| Format: | Preprint |
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2025
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| _version_ | 1866910897915559936 |
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| author | Chen, Chuan-Hung Chiang, Cheng-Wei de la Vega, Leon M. G. |
| author_facet | Chen, Chuan-Hung Chiang, Cheng-Wei de la Vega, Leon M. G. |
| contents | Right-handed neutrinos $ν_R$ play a crucial role in flavor-changing neutral-current processes with missing energy, such as $b\to s + \slashed{E} $ and $d\to s + \slashed{E} $, where Belle-II reports unexpectedly large branching fraction in $B\to K ν\barν$ decays. Assuming $ν_R$ is the partner of the active neutrino $ν_L$ in the standard model, a Dirac-type neutrino framework emerges. We investigate a scenario of radiative Dirac neutrino mass generation in a scalar leptoquark (LQ) model with a global $U(1)_X$ symmetry to suppress Majorana mass, tree-level Dirac mass, and diquark couplings. The simplest LQ realization consists of two $S_1 = (3,1,-1/3)$ LQs with distinct $U(1)_X$ charges. A non-Casas-Ibarra parametrization is proposed to match neutrino data with fewer model parameters. Imposing current experimental constraints from meson mixing and lepton flavor-violating processes, we find that right-handed neutrino effects can significantly enhance $B\to K^{(*)} ν\barν$ and $K^+\to π^+ ν\barν$. Additionally, the model predicts excesses in $R_D$ from $B\to Dτ\barν$ that remain within $1σ$ of current experimental data. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2503_22431 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Leptoquark-mediated Dirac neutrino mass and its impact on $B \to K ν\barν$ and $K \to πν\barν$ decays Chen, Chuan-Hung Chiang, Cheng-Wei de la Vega, Leon M. G. High Energy Physics - Phenomenology High Energy Physics - Experiment Right-handed neutrinos $ν_R$ play a crucial role in flavor-changing neutral-current processes with missing energy, such as $b\to s + \slashed{E} $ and $d\to s + \slashed{E} $, where Belle-II reports unexpectedly large branching fraction in $B\to K ν\barν$ decays. Assuming $ν_R$ is the partner of the active neutrino $ν_L$ in the standard model, a Dirac-type neutrino framework emerges. We investigate a scenario of radiative Dirac neutrino mass generation in a scalar leptoquark (LQ) model with a global $U(1)_X$ symmetry to suppress Majorana mass, tree-level Dirac mass, and diquark couplings. The simplest LQ realization consists of two $S_1 = (3,1,-1/3)$ LQs with distinct $U(1)_X$ charges. A non-Casas-Ibarra parametrization is proposed to match neutrino data with fewer model parameters. Imposing current experimental constraints from meson mixing and lepton flavor-violating processes, we find that right-handed neutrino effects can significantly enhance $B\to K^{(*)} ν\barν$ and $K^+\to π^+ ν\barν$. Additionally, the model predicts excesses in $R_D$ from $B\to Dτ\barν$ that remain within $1σ$ of current experimental data. |
| title | Leptoquark-mediated Dirac neutrino mass and its impact on $B \to K ν\barν$ and $K \to πν\barν$ decays |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2503.22431 |