A search for charginos nearly mass-degenerate with the lightest supersymmet
ric particle is performed using the 176 pb(-1) of data collected at 189 GeV
in 1998 with the L3 detector. Mass differences between the chargino and th
e lightest supersymmetric particle below 4 GeV are considered. The presence
of a high transverse momentum photon is required to single out the signal
from the photon-photon interaction background. Na evidence for charginos is
found and upper Limits on the cross section for chargino pail production a
re set, For the first time at LEP2, in the case of heavy scalar leptons, ch
argino <(chi)over tilde>(+/-)(1) - <(chi)over tilde>(0)(1) mass difference.
(C) 2000 Published by Elsevier Science B.V. All rights reserved.