These limits are from ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \tau}^{*}}{{\mathit \tau}}$ and depend on transition magnetic coupling between ${{\mathit \tau}}$ and ${{\mathit \tau}^{*}}$. All limits assume ${{\mathit \tau}^{*}}$ $\rightarrow$ ${{\mathit \tau}}{{\mathit \gamma}}$ decay. Limits from LEP are for chiral coupling, whereas all other limits are for nonchiral coupling, ${{\mathit \eta}_{{L}}}$ = ${{\mathit \eta}_{{R}}}$ = 1. In most papers, the limit is expressed in the form of an excluded region in the $\lambda −{\mathit m}_{{{\mathit \tau}^{*}}}$ plane. See the original papers.

VALUE (GeV) CL% DOCUMENT ID TECN  COMMENT $\bf{> 2500}$ 95 1 AAD 2015 AP ATLS ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \tau}^{(*)}}{{\mathit \tau}^{*}}{{\mathit X}}$ • • We do not use the following data for averages, fits, limits, etc. • • $>180$ 95 2 ACHARD 2003 B L3 ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \tau}}{{\mathit \tau}^{*}}$ $>185$ 95 3 ABBIENDI 2002 G OPAL ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \tau}}{{\mathit \tau}^{*}}$ 1  AAD 2015AP search for ${{\mathit \tau}^{*}}$ production in events with three or more charged leptons in ${{\mathit p}}{{\mathit p}}$ collisions at $\sqrt {s }$ = 8 TeV. The quoted limit assumes ${{\mathit \Lambda}}$ = ${\mathit m}_{{{\mathit \tau}^{*}}}$, ${{\mathit f}}$ = ${{\mathit f}^{\,'}}$ = 1. The contact interaction is included in the ${{\mathit \tau}^{*}}$ production and decay amplitudes. 2  ACHARD 2003B result is from ${{\mathit e}^{+}}{{\mathit e}^{-}}$ collisions at $\sqrt {\mathit s }$ = $189 - 209$ GeV. ${{\mathit f}}$ = ${{\mathit f}^{\,'}}$ = $\Lambda /{\mathit m}_{{{\mathit \tau}^{*}}}$ is assumed. See their Fig.$~$4 for the exclusion plot in the mass-coupling plane. 3  ABBIENDI 2002G result is from ${{\mathit e}^{+}}{{\mathit e}^{-}}$ collisions at $\sqrt {\mathit s }$ = $183 - 209$ GeV. ${{\mathit f}}$ = ${{\mathit f}^{\,'}}$ = $\Lambda /{\mathit m}_{{{\mathit \tau}^{*}}}$ is assumed for ${{\mathit \tau}^{*}}$ coupling. See their Fig.$~$4c for the exclusion limit in the mass-coupling plane.

References:

AAD 2015AP JHEP 1508 138 Search for New Phenomena in Events with Three or More Charged Leptons in ${{\mathit p}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 8 TeV with the ATLAS Detector ACHARD 2003B PL B568 23 Search for Excited Leptons at LEP ABBIENDI 2002G PL B544 57 Search for Charged Excited Leptons in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Collisions at $\sqrt {s }$ = 183-GeV to 209-GeV