Correlating lepton flavour violating $b \to s$ and leptonic decay modes in a minimal abelian extension of the Standard Model
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arXiv
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| Natura: | Preprint |
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2025
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| _version_ | 1866908676869062656 |
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| author | Colangelo, Pietro De Fazio, Fulvia Milillo, Davide |
| author_facet | Colangelo, Pietro De Fazio, Fulvia Milillo, Davide |
| contents | We consider an abelian extension of the Standard Model (SM) comprising a new gauge group $U(1)^\prime$, with the neutral gauge boson $Z^\prime$ having flavour violating couplings to quarks and leptons. The fermion content is the same as in SM except for the addition of three right-handed neutrinos. The model, proposed in \cite{Aebischer:2019blw}, describes the couplings of $Z^\prime$ to fermions in terms of three rational parameters $ε_{1,2,3}$ that sum to zero imposing the cancellation of the gauge anomalies. Each $ε_i$ is common to all fermions in a generation, a feature producing correlations among quark and lepton observables. We focus on $b \to s \ell_1^- \ell_2^+$ transitions for the lepton flavour conserving $\ell_1=\ell_2$ and lepton flavour violating case $\ell_1 \neq \ell_2$. Small deviations with respect to the SM predictions are found in the first case, which reflects a feature of the model where quark and lepton sectors prevent each other to manifest large discrepancies with respect to SM. We investigate the correlations between rare $B$ and $B_s$ decays and the leptonic processes $τ^- \to μ^- μ^+ μ^-$, $μ^- \to e^- γ$, $μ^- \to e^- e^+ e^-$ and the $ μ^- \to e^-$ conversion in nuclei. We show that the current experimental upper bounds on these four channels play an increasingly important role in constraining the branching fractions of lepton flavour violating $B$ and $B_s$ decays. While the present bound on $τ^- \to μ^- μ^+ μ^-$ does not impose significant restrictions, the other three modes set progressively more stringent limits, an important information for the planned new experimental facilities. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2506_02552 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Correlating lepton flavour violating $b \to s$ and leptonic decay modes in a minimal abelian extension of the Standard Model Colangelo, Pietro De Fazio, Fulvia Milillo, Davide High Energy Physics - Phenomenology High Energy Physics - Experiment High Energy Physics - Lattice We consider an abelian extension of the Standard Model (SM) comprising a new gauge group $U(1)^\prime$, with the neutral gauge boson $Z^\prime$ having flavour violating couplings to quarks and leptons. The fermion content is the same as in SM except for the addition of three right-handed neutrinos. The model, proposed in \cite{Aebischer:2019blw}, describes the couplings of $Z^\prime$ to fermions in terms of three rational parameters $ε_{1,2,3}$ that sum to zero imposing the cancellation of the gauge anomalies. Each $ε_i$ is common to all fermions in a generation, a feature producing correlations among quark and lepton observables. We focus on $b \to s \ell_1^- \ell_2^+$ transitions for the lepton flavour conserving $\ell_1=\ell_2$ and lepton flavour violating case $\ell_1 \neq \ell_2$. Small deviations with respect to the SM predictions are found in the first case, which reflects a feature of the model where quark and lepton sectors prevent each other to manifest large discrepancies with respect to SM. We investigate the correlations between rare $B$ and $B_s$ decays and the leptonic processes $τ^- \to μ^- μ^+ μ^-$, $μ^- \to e^- γ$, $μ^- \to e^- e^+ e^-$ and the $ μ^- \to e^-$ conversion in nuclei. We show that the current experimental upper bounds on these four channels play an increasingly important role in constraining the branching fractions of lepton flavour violating $B$ and $B_s$ decays. While the present bound on $τ^- \to μ^- μ^+ μ^-$ does not impose significant restrictions, the other three modes set progressively more stringent limits, an important information for the planned new experimental facilities. |
| title | Correlating lepton flavour violating $b \to s$ and leptonic decay modes in a minimal abelian extension of the Standard Model |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment High Energy Physics - Lattice |
| url | https://arxiv.org/abs/2506.02552 |