The Standard Model predicts that the τ lepton-flavour-violating (LFV) branching fractions are too small to be measured with the available experimental precision. We report in Table 14 and Figure 2 the experimental upper limits on these branching fractions that have been published by the B-factories BaBar and Belle and later experiments. We omit previous weaker upper limits (mainly from CLEO) and all preliminary results presented several years ago. The previous HFLAV report [4] still included a few preliminary results, which have all been removed now.
Decay mode Category
90% CL Limit Exp. Ref. Γ156 = e− γ ℓγ 3.3 · 10−8 BaBar [92] Γ156 = e− γ 1.2 · 10−7 Belle [93] Γ157 = µ− γ 4.4 · 10−8 BaBar [92] Γ157 = µ− γ 4.5 · 10−8 Belle [93] Γ158 = e− π0 ℓ P0 1.3 · 10−7 BaBar [94] Γ158 = e− π0 8.0 · 10−8 Belle [95] Γ159 = µ− π0 1.1 · 10−7 BaBar [94] Γ159 = µ− π0 1.2 · 10−7 Belle [95] Γ160 = e− KS0 3.3 · 10−8 BaBar [96] Γ160 = e− KS0 2.6 · 10−8 Belle [97] Γ161 = µ− KS0 4.0 · 10−8 BaBar [96] Γ161 = µ− KS0 2.3 · 10−8 Belle [97] Γ162 = e− η 1.6 · 10−7 BaBar [94] Γ162 = e− η 9.2 · 10−8 Belle [95] Γ163 = µ− η 1.5 · 10−7 BaBar [94] Γ163 = µ− η 6.5 · 10−8 Belle [95] Γ172 = e− η′(958) 2.4 · 10−7 BaBar [94] Γ172 = e− η′(958) 1.6 · 10−7 Belle [95] Γ173 = µ− η′(958) 1.4 · 10−7 BaBar [94] Γ173 = µ− η′(958) 1.3 · 10−7 Belle [95] Γ164 = e− ρ0 ℓ V0 4.6 · 10−8 BaBar [98] Γ164 = e− ρ0 1.8 · 10−8 Belle [99] Γ165 = µ− ρ0 2.6 · 10−8 BaBar [98] Γ165 = µ− ρ0 1.2 · 10−8 Belle [99] Γ166 = e− ω 1.1 · 10−7 BaBar [100] Γ166 = e− ω 4.8 · 10−8 Belle [99] Γ167 = µ− ω 1.0 · 10−7 BaBar [100] Γ167 = µ− ω 4.7 · 10−8 Belle [99] Γ168 = e− K*(892)0 5.9 · 10−8 BaBar [98] Γ168 = e− K*(892)0 3.2 · 10−8 Belle [99] Γ169 = µ− K*(892)0 1.7 · 10−7 BaBar [98] Γ169 = µ− K*(892)0 7.2 · 10−8 Belle [99] Γ170 = e− K*(892)0 4.6 · 10−8 BaBar [98] Γ170 = e− K*(892)0 3.4 · 10−8 Belle [99] Γ171 = µ− K*(892)0 7.3 · 10−8 BaBar [98] Γ171 = µ− K*(892)0 7.0 · 10−8 Belle [99] Γ176 = e− φ 3.1 · 10−8 BaBar [98] Γ176 = e− φ 3.1 · 10−8 Belle [99] Γ177 = µ− φ 1.9 · 10−7 BaBar [98] Γ177 = µ− φ 8.4 · 10−8 Belle [99] Γ174 = e− f0(980) ℓ S0 3.2 · 10−8 Belle [101] Γ175 = µ− f0(980) 3.4 · 10−8 Belle [101] Γ178 = e− e+ e− ℓℓℓ 2.9 · 10−8 BaBar [102] Γ178 = e− e+ e− 2.7 · 10−8 Belle [103] Γ179 = e− µ+ µ− 3.2 · 10−8 BaBar [102] Γ179 = e− µ+ µ− 2.7 · 10−8 Belle [103] Γ180 = µ− e+ µ− 2.6 · 10−8 BaBar [102] Γ180 = µ− e+ µ− 1.7 · 10−8 Belle [103] Γ181 = µ− e+ e− 2.2 · 10−8 BaBar [102] Γ181 = µ− e+ e− 1.8 · 10−8 Belle [103] Γ182 = e− µ+ e− 1.8 · 10−8 BaBar [102] Γ182 = e− µ+ e− 1.5 · 10−8 Belle [103] Γ183 = µ− µ+ µ− 3.8 · 10−7 ATLAS [104] Γ183 = µ− µ+ µ− 3.3 · 10−8 BaBar [102] Γ183 = µ− µ+ µ− 2.1 · 10−8 Belle [103] Γ183 = µ− µ+ µ− 4.6 · 10−8 LHCb [105] Γ184 = e− π+ π− ℓ hh 1.2 · 10−7 BaBar [106] Γ184 = e− π+ π− 2.3 · 10−8 Belle [107] Γ185 = e+ π− π− 2.7 · 10−7 BaBar [106] Γ185 = e+ π− π− 2.0 · 10−8 Belle [107] Γ186 = µ− π+ π− 2.9 · 10−7 BaBar [106] Γ186 = µ− π+ π− 2.1 · 10−8 Belle [107] Γ187 = µ+ π− π− 7.0 · 10−8 BaBar [106] Γ187 = µ+ π− π− 3.9 · 10−8 Belle [107] Γ188 = e− π+ K− 3.2 · 10−7 BaBar [106] Γ188 = e− π+ K− 3.7 · 10−8 Belle [107] Γ189 = e− K+ π− 1.7 · 10−7 BaBar [106] Γ189 = e− K+ π− 3.1 · 10−8 Belle [107] Γ190 = e+ π− K− 1.8 · 10−7 BaBar [106] Γ190 = e+ π− K− 3.2 · 10−8 Belle [107] Γ191 = e− KS0 KS0 7.1 · 10−8 Belle [97] Γ192 = e− K+ K− 1.4 · 10−7 BaBar [106] Γ192 = e− K+ K− 3.4 · 10−8 Belle [107] Γ193 = e+ K− K− 1.5 · 10−7 BaBar [106] Γ193 = e+ K− K− 3.3 · 10−8 Belle [107] Γ194 = µ− π+ K− 2.6 · 10−7 BaBar [106] Γ194 = µ− π+ K− 8.6 · 10−8 Belle [107] Γ195 = µ− K+ π− 3.2 · 10−7 BaBar [106] Γ195 = µ− K+ π− 4.5 · 10−8 Belle [107] Γ196 = µ+ π− K− 2.2 · 10−7 BaBar [106] Γ196 = µ+ π− K− 4.8 · 10−8 Belle [107] Γ197 = µ− KS0 KS0 8.0 · 10−8 Belle [97] Γ198 = µ− K+ K− 2.5 · 10−7 BaBar [106] Γ198 = µ− K+ K− 4.4 · 10−8 Belle [107] Γ199 = µ+ K− K− 4.8 · 10−7 BaBar [106] Γ199 = µ+ K− K− 4.7 · 10−8 Belle [107] Γ211 = π− Λ BNV 7.2 · 10−8 Belle [108] Γ212 = π− Λ 1.4 · 10−7 Belle [108] Γ215 = p µ− µ− 4.4 · 10−7 LHCb [109] Γ216 = p µ+ µ− 3.3 · 10−7 LHCb [109]