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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2603.00635 |
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| _version_ | 1866914361257230336 |
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| author | Jodłowski, Krzysztof Lu, Chih-Ting |
| author_facet | Jodłowski, Krzysztof Lu, Chih-Ting |
| contents | The singlet majoron $J$ is the pseudo-Nambu-Goldstone boson of a global, anomaly-free $U(1)_{B-L}$ symmetry whose spontaneous breaking generates Majorana masses for right-handed neutrinos. At tree level, the only direct coupling of $J$ to Standard Model fields is $Jνν\propto m_ν/f$ (where $m_ν$ denotes the light neutrino mass and $f$ the $B-L$ breaking scale). Couplings to charged fermions and gauge bosons, in contrast, arise only at loop level. Consequently, $J$ can be long-lived over wide regions of parameter space, motivating displaced-decay searches. We study majoron production and displaced decays at proton beam dump experiments, neutrino facilities, and LHC forward detectors (including DUNE, NA62, FASER/FASER2, MATHUSLA, and SHiP), and we quantify the resulting reach in the $(m_J,\,f)$ plane. We show that, for realistic seesaw-induced coupling textures, lepton-flavor-violating (LFV) $τ$ decays $τ\to \ell J$ ($\ell=e,μ$) dominate majoron production at these facilities and can extend sensitivity into the intermediate-mass window $m_J\simeq 0.2\text{-}1.7~\mathrm{GeV}$, complementary to supernova bounds at lower masses and to dedicated LFV searches at higher masses. We also identify physically consistent benchmark textures for the matrix $K=M_D M_D^\dagger/(vf)$ with $M_D$ denoting the Dirac mass matrix and $v$ the electroweak scale (including positive semidefinite ``anarchical'', single-flavor, and CP-violating cases) and map their impact on experimental reach. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_00635 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Impact of flavor changing processes on prospects for majoron discovery at intensity-frontier searches Jodłowski, Krzysztof Lu, Chih-Ting High Energy Physics - Phenomenology The singlet majoron $J$ is the pseudo-Nambu-Goldstone boson of a global, anomaly-free $U(1)_{B-L}$ symmetry whose spontaneous breaking generates Majorana masses for right-handed neutrinos. At tree level, the only direct coupling of $J$ to Standard Model fields is $Jνν\propto m_ν/f$ (where $m_ν$ denotes the light neutrino mass and $f$ the $B-L$ breaking scale). Couplings to charged fermions and gauge bosons, in contrast, arise only at loop level. Consequently, $J$ can be long-lived over wide regions of parameter space, motivating displaced-decay searches. We study majoron production and displaced decays at proton beam dump experiments, neutrino facilities, and LHC forward detectors (including DUNE, NA62, FASER/FASER2, MATHUSLA, and SHiP), and we quantify the resulting reach in the $(m_J,\,f)$ plane. We show that, for realistic seesaw-induced coupling textures, lepton-flavor-violating (LFV) $τ$ decays $τ\to \ell J$ ($\ell=e,μ$) dominate majoron production at these facilities and can extend sensitivity into the intermediate-mass window $m_J\simeq 0.2\text{-}1.7~\mathrm{GeV}$, complementary to supernova bounds at lower masses and to dedicated LFV searches at higher masses. We also identify physically consistent benchmark textures for the matrix $K=M_D M_D^\dagger/(vf)$ with $M_D$ denoting the Dirac mass matrix and $v$ the electroweak scale (including positive semidefinite ``anarchical'', single-flavor, and CP-violating cases) and map their impact on experimental reach. |
| title | Impact of flavor changing processes on prospects for majoron discovery at intensity-frontier searches |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2603.00635 |