G. Abbiendi et al., Search for acoplanar lepton pair events in e(+)e(-) collisions at root s=161, 172, and 183 GeV, EUR PHY J C, 12(4), 2000, pp. 551-565
A selection of di-lepton events with significant missing transverse momentu
m has been performed using a total data sample of 77.0 pb(-1) at e(+)e(-) c
entre-of-mass energies of 161 GeV, 172 GeV and 183 GeV. The observed number
s of events: four at 161 GeV, nine at 172 GeV, and 78 at 183 GeV, are consi
stent with the numbers expected from Standard Model processes, which arise
predominantly from W+W- production with each W decaying leptonically. This
topology is an experimental signature also for the pair production of new p
articles that decay to a charged lepton accompanied by one or more invisibl
e particles. Further event selection criteria are described that optimise t
he sensitivity to particular new physics channels. No evidence for new phen
omena is apparent and limits on the production cross-section times branchin
g ratio squared for various new physics processes are presented in a manner
intended to minimise the number of model assumptions. Assuming a 100% bran
ching ratio for the decay rho(R)(+/-) --> rho(+/-) <(chi)over tilde>(0)(1),
we exclude aat 95% CL: right-handed smuons with masses below 65 GeV for m(
<(mu)over) (tilde>) - m(<(chi)over tilde>1)(0) > 2 GeV and right-handed sta
tus with masses below 64 GeV for m(<(tau)over tilde>-) - m(<(chi)over tilde
>1)(0) > 10 GeV. Right-handed selectrons are excluded at 95% CL for masses
below 77 GeV for m((o) over tilde-) - m(<(chi)over tilde>1)(0) > 5 GeV with
in the framework of the Minimal Supersymmetric Standard Model assuming mu <
-100 GeV and tan beta = 1.5.