1DORENBOSCH 1989 obtain the limit $\lambda {}^{2}_{\gamma }\Lambda {}^{2}_{{\mathrm {cut}}}/{{\mathit m}^{2}}_{{{\mathit e}^{*}}}$ $<$ $2.6$ (95$\%$ CL), where $\Lambda _{{\mathrm {cut}}}$ is the cutoff scale, based on the one-loop calculation by GRIFOLS 1986. If one assumes that $\Lambda _{{\mathrm {cut}}}$ = 1 TeV and ${{\mathit \lambda}_{{{\gamma}}}}$ = 1, one obtains ${\mathit m}_{{{\mathit e}^{*}}}$ $>$ 620 GeV. However, one generally expects ${{\mathit \lambda}_{{{\gamma}}}}{}\approx{}{\mathit m}_{{{\mathit e}^{*}}}/\Lambda _{{\mathrm {cut}}}$ in composite models.
2GRIFOLS 1986 uses ${{\mathit \nu}_{{{\mu}}}}$ ${{\mathit e}}$ $\rightarrow$ ${{\mathit \nu}_{{{\mu}}}}{{\mathit e}}$ and ${{\overline{\mathit \nu}}_{{{\mu}}}}$ ${{\mathit e}}$ $\rightarrow$ ${{\overline{\mathit \nu}}_{{{\mu}}}}{{\mathit e}}$ data from CHARM Collaboration to derive mass limits which depend on the scale of compositeness.
3RENARD 1982 derived from $\mathit g-2$ data limits on mass and couplings of ${{\mathit e}^{*}}$ and ${{\mathit \mu}^{*}}$. See figures 2 and 3 of the paper.
References:
DORENBOSCH
1989
ZPHY C41 567
Experimental Results on Neutrino Electron Scattering
GRIFOLS
1986
PL 168B 264
Limits on Masses of Excited Electrons and Muons from Neutrino Scattering off Electrons
RENARD
1982
PL 116B 264
Limits on Masses and Couplings of Excited Electrons and Muons
