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Search for Lepton Flavor Violating tau^- Decays into \ell^-\eta, \ell^-\eta' and \ell^-\pi^0
High Energy Physics - Experiment · Submitted 4 Mar 2007
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim No evidence for these decays is found and we set the following upper limits on the branching fractions: ${\cal{B}}(\tau^-\to e^-\eta) < 9.2\times 10^{-8}$, ${\cal{B}}(\tau^-\to \mu^-\eta) < 6.5\times 10^{-8}$, ${\cal{B}}(\tau^-\to e^-\eta') < 1.6\times 10^{-7}$, ${\cal{B}}(\tau^-\to \mu^-\eta') < 1.3\times 10^{-7}$, ${\cal{B}}(\tau^-\to e^-\pi^0) < 8.0\times 10^{-8}$ and ${\cal{B}}(\tau^-\to \mu^-\pi^0) < 1.2\times 10^{-7}$ at the 90% confidence level.
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We have searched for lepton-flavor-violating $\tau$ decays with a pseudoscalar meson ($\eta$, $\eta'$ {and} $\pi^0$) using a data sample of 401 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No evidence for these decays is found and we set the following upper limits on the branching fractions: ${\cal{B}}(\tau^-\to e^-\eta) < 9.2\times 10^{-8}$, ${\cal{B}}(\tau^-\to \mu^-\eta) < 6.5\times 10^{-8}$, ${\cal{B}}(\tau^-\to e^-\eta') < 1.6\times 10^{-7}$, ${\cal{B}}(\tau^-\to \mu^-\eta') < 1.3\times 10^{-7}$, ${\cal{B}}(\tau^-\to e^-\pi^0) < 8.0\times 10^{-8}$ and ${\cal{B}}(\tau^-\to \mu^-\pi^0) < 1.2\times 10^{-7}$ at the 90% confidence level. These results improve our previously published upper limits by factors from 2.3 to 6.3.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We have searched for lepton-flavor-violating $\tau$ decays with a pseudoscalar meson ($\eta$, $\eta'$ {and} $\pi^0$) using a data sample of 401 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. | method 0.50 | 0.97 | 0.04 | asserted 0.99 |
| s1 | No evidence for these decays is found and we set the following upper limits on the branching fractions: ${\cal{B}}(\tau^-\to e^-\eta) < 9.2\times 10^{-8}$, ${\cal{B}}(\tau^-\to \mu^-\eta) < 6.5\times 10^{-8}$, ${\cal{B}}(\tau^-\to e^-\eta') < 1.6\times 10^{-7}$, ${\cal{B}}(\tau^-\to \mu^-\eta') < 1.3\times 10^{-7}$, ${\cal{B}}(\tau^-\to e^-\pi^0) < 8.0\times 10^{-8}$ and ${\cal{B}}(\tau^-\to \mu^-\pi^0) < 1.2\times 10^{-7}$ at the 90% confidence level. | result 1.00 | 0.98 | 0.93 | asserted 1.00 |
| s2 | These results improve our previously published upper limits by factors from 2.3 to 6.3. | interpretation 0.74 | 0.87 | 0.10 | asserted 1.00 |
What was examined, and what was not
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The paper
Original abstract
We have searched for lepton-flavor-violating $\tau$ decays with a pseudoscalar meson ($\eta$, $\eta'$ {and} $\pi^0$) using a data sample of 401 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No evidence for these decays is found and we set the following upper limits on the branching fractions: ${\cal{B}}(\tau^-\to e^-\eta) < 9.2\times 10^{-8}$, ${\cal{B}}(\tau^-\to \mu^-\eta) < 6.5\times 10^{-8}$, ${\cal{B}}(\tau^-\to e^-\eta') < 1.6\times 10^{-7}$, ${\cal{B}}(\tau^-\to \mu^-\eta') < 1.3\times 10^{-7}$, ${\cal{B}}(\tau^-\to e^-\pi^0) < 8.0\times 10^{-8}$ and ${\cal{B}}(\tau^-\to \mu^-\pi^0) < 1.2\times 10^{-7}$ at the 90% confidence level. These results improve our previously published upper limits by factors from 2.3 to 6.3.
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References
How the literature uses it
15 arXiv papers cite this in 16 sentences
Papers whose main result relates to this one's
States the same result 1 paper
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No evidence for these decays is found and we set the following upper limits on the branching fractions: ${\cal{B}}(\tau^-\to e^-\eta) < 9.2\times 10^{-8}$, ${\cal{B}}(\tau^-\to \mu^-\eta) < 6.5\times 10^{-8}$, ${\cal{B}}(\tau^-\to e^-\eta') < 1.6\times 10^{-7}$, ${\cal{B}}(\tau^-\to \mu^-\eta') < 1.3\times 10^{-7}$ ${\cal{B}}(\tau^-\to e^-\pi^0) < 8.0\times 10^{-8}$ and ${\cal{B}}(\tau^-\to \mu^-\pi^0) < 1.2\times 10^{-7}$ at the 90% confidence level, respectively.
Search for Lepton Flavor Violating tau^- Decays into l^-eta, l^-eta' and l^-pi^0 · 1.00
Papers citing it · 10 sentences without a confident label
Uses its data or values 5 papers
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$e^-γ$ Belle [ref] 988 5.6$×10^-8$ Belle II [ref] 50 9.0$×10^-9$ BaBar [ref] 516 3.3$×10^-8$ $μ^-γ$ Belle [ref] 988 4.2$×10^-8$ Belle II [ref] 50 6.9$×10^-9$ BaBar [ref] 516 4.4$×10^-8$ STCF [ref] 1 1.2$×10^-8$ FCC-ee [ref] 150 $O(10^-9)$ $e^-π^0$ Belle [ref] 401 8.0$×10^-8$ Belle II [ref] 50 7.3$×10^-10$ BaBar [ref] 339 1.3$×10^-7$ $μ^-π^0$ Belle [ref] 401 1.2$×10^-7$ Belle II [ref] 50 7.1$×10^-10$ BaBar [ref] 339 1.1$×10^-7$ $e^- K_S^0$ Belle [ref] 671 2.6$×10^-8$ Belle II [ref] 50 4.0$×10^-10$ BaBar [ref] 469 3.3$×10^-8$ $μ^- K_S^0$ Belle [ref] 671 2.3$×10^-8$ Belle II [ref] 50 4.0$×10^-10$ BaBar [ref] 469 4.0$×10^-8$ $e^- η$ Belle [ref] 401 9.2$×10^-8$ Belle II [ref] 50 1.2$×10^-9$ BaBar [ref] 339 1.6$×10^-7$ $μ^-η$ Belle [ref] 401 6.5$×10^-8$ Belle II [ref] 50 8.0$×10^-10$ BaBar [ref] 339 1.5$×10^-7$ $e^-η^'$ Belle [ref] 401 1.6$×10^-7$ Belle II [ref] 50 1.2$×10^-9$ BaBar [ref] 339
Snowmass 2021 White Paper: Charged lepton flavor violation in the tau sector · Experimental Summary · 0.95
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The scenarios considered in our study must satisfy rare $B$-decay constraints [ref] , BR(B^0 →X_s γ) ∈[2.99,3.87]×10^-4 , BR(B^0_s →μ^+μ^-) ∈[1.1, 6.4] ×10^-9 and BR(B →τν_τ)/BR_SM(B →τν_τ) ∈[0.15,2.41] , rare tau-decay constraints [ref] , BR(τ→e γ) ∈[0, 3.3] ×10^-8 , BR(τ→μγ) ∈[0, 4.4] ×10^-8 , BR(τ→e π) ∈[0, 8.0] ×10^-8 , BR(τ→μπ) ∈[0, 1.1] ×10^-7 , BR(τ→3μ) ∈[0, 2.1] ×10^-8 , $B$-meson oscillation constraints [ref] , ΔM_s ∈[10.2,26.4] ps^-1 , ΔM_d ∈[0.29,0.76] ps^-1 , and flavour-violating $Z$-boson [ref] and Higgs-boson [ref] decay bounds, BR(Z→e μ) ∈[0, 7.5]×10^-7 and BR(h →e μ) ∈[0, 3.5] ×10^-4 .
Exploring vector-like supersymmetric extensions of the Standard Model with dark matter and colliders · Analysis setup and experimental constraints · 0.97
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The bounds are T_1^(π^0) ≲ [ Br(τ^- →π^0 e^-)/8.0 ×10^-8] (5.0 TeV)^-4 , [ref] T_2^(π^0) ≲ [ Br(τ^- →π^0 μ^- )/1.1 ×10^-7 ] (4.7 TeV)^-4 , [ref] T_1^(K^0_S) ≲ [ Br(τ^- →K^0_S e^-)/2.6 ×10^-8 ] (8.4 TeV)^-4 , [ref] T_2^(K^0_S) ≲ [ Br(τ^- →K^0_S μ^- )/2.3 ×10^-8] (8.6 TeV)^-4 .
Left-Right SU(4) Vector Leptoquark Model for Flavor Anomalies · Flavor constraints: Model-independent analysis · 0.98
Cites it as background 1 paper
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Recently, a global analysis of low-energy charged LFV (cLFV) observables [ref] was carried out in [ref] , identifying the presence of poorly-constrained directions involving semileptonic operators.
Improving the Global SMEFT Picture with Bounds on Neutrino NSI · Global analysis of flavour violating operators · 0.88
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