Search for R-parity violation with a (U)over-bar(D)over-bar(D)over-bar coupling at root s approximate to 189 GeV

Searches for pair production of gauginos and squarks in e(+)e(-) collisions at a centre-of-mass energy of 189 GeV have been performed on data corresponding to an integrated luminosity of 158 pb(-1) collected by the DELPHI detector at LEP. The data were analyzed under the assumption of non-conservation of R-parity through a single dominant (U) over bar(D) over bar(D) over bar coupling between squarks and quarks. Typical final states contain between 4 and 10 jets with or without additional leptons. No excess of data above Standard Model expectations was observed. The results were used to constrain domains of the MSSM parameter space and derive limits on the masses of supersymmetric particles. The following mass limits at 95% CL were obtained from these searches: neutralino mass: m(<(<chi>)over tilde>1)(0) greater than or equal to 32 GeV; chargino mass: m(<(<chi>)over tilde>1)(+) greater than or equal to 94 GeV; stop and sboctom mass (indirect decay) with DeltaM > 5 GeV: m((t) over tilde1) greater than or equal to 74 GeV for Phi (mix) = 0 rad, m((t) over tilde1) greater than or equal to 59 GeV for Phi (mix) = 0.98 rad, m((b) over tilde1) greater than or equal to 72 GeV for Phi (mix) = 0 rad. The angle phi (mix) is the mixing angle between left and right handed quarks. (C) 2001 Elsevier Science B.V. All rights reserved.