A search for neutral Higgs bosons has been performed using the full sample of Z 0 decays collected by the OPAL detector at LEP up to 1995. The data were taken at centre-of-mass energies between 88 GeV and 95 GeV and correspond to an integrated luminosity of approximately 160 pb 1. The present search addresses the processes Z 0 !H 0 Z and h 0 Z , where H 0 is the Higgs boson predicted by the Standard Model and h 0 the lightest neutral scalar Higgs boson predicted in the framework of the Minimal Supersymmetric Standard Model. For the virtual Z 0 boson, Z , the following decay c hannels are considered: Z ! , e + e and +. One candidate event

A search for a supersymmetric partner of the top quark (t 1 ) has been performed by the OPAL experiment i n e + e collisions at LEP. The integrated luminosity of the data sample analysed was 69.1 pb 1 , which corresponds to 1.6810 6 produced Z 0 ! q q e v ents. Not 1 candidates have been found. This study excludes the existence of thet 1 with a mass below 45.1 GeV at 95% C.L., where the mixing angle of left-and right-handed partners is smaller than 0.85 rad or greater than 1.15 rad, and the mass dierence between thet 1 and the lightest neutralino is greater than 5 GeV.

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We h a v e searched for lepton avour violating Z 0 !e, Z 0 ! e and Z 0 ! decays in a sample of 4:0 10 6 visible Z 0 decays collected with the OPAL detector at LEP during 1991 to 1994. No candidates are found for Z 0 !e. The samples of selected Z 0 !e and Z 0 ! candidates are consistent with the expected background. The following limits are set at 95% condence level:BR(Z 0 ! e) < 1:7 10 6

Measurements of helicity density matrix elements have been made for the (1020), D and B vector mesons in multihadronic Z 0 decays in the OPAL experiment a t L E P . Results for inclusive produced with high energy show evidence for production preferentially in the helicity zero state, with 00 = 0 : 54 0:08, compared to the value of 1/3 expected for no spin alignment. The corresponding element for the D h a s a v alue of 0:400:02, also suggesting a deviation from 1/3. The B result, with 00 = 0 : 36 0:09, is consistent with no spin alignment. O-diagonal elements have been measured for the and D mesons; for the D the element R e 1 1 is non-zero, indicating non-independent fragmentation of the primary quarks.