# Determination of the $e^+ e^- \to \gamma \gamma(\gamma)$ cross-section at centre-of-mass energies ranging from 189 GeV to 202 GeV

Abstract : A test of the QED process \eeintogg(\fot) is reported. The data analysed were collected with the DELPHI detector in 1998 and 1999 at the highest ener\-gies achieved at LEP, reaching 202 GeV in the centre-of-mass. The total integrated luminosity amounts to 375.7 pb$^{-1}$. The differential and total cross-sections for the process $e^+e^- \to \gamma \gamma$ were measured, and found to be in agreement with the QED prediction. 95\% Confidence Level (C.L.) lower limits on the QED cut-off parameters of $\rm \Lambda_+$ 330 GeV and $\rm \Lambda_{-}>$ 320 GeV were derived. A 95\% C.L. lower bound on the mass of an excited electron of 311 $\rm GeV/c^2$ (for $\lambda_{\gamma}$ =1) was obtained. s-channel virtual graviton exchange was searched for, resulting in 95\% C.L. lower limits on the string mass scale, $\rm M_S$: $\rm M_S 713 \, GeV/c^2$ ( $\lambda=1$) and $\rm M_S 691 \,GeV/c^2$ ($\lambda = -1$).
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Journal articles

Cited literature [4 references]

http://hal.in2p3.fr/in2p3-00006140
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Submitted on : Friday, October 27, 2000 - 6:15:21 PM
Last modification on : Tuesday, October 19, 2021 - 11:00:06 PM

### Identifiers

• HAL Id : in2p3-00006140, version 1

### Citation

P. Abreu, W. Adam, T. Adye, P. Adzic, Z. Albrecht, et al.. Determination of the $e^+ e^- \to \gamma \gamma(\gamma)$ cross-section at centre-of-mass energies ranging from 189 GeV to 202 GeV. Physics Letters B, Elsevier, 2000, 491, pp.67-80. ⟨in2p3-00006140⟩

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