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We summarize a search for the top quark with the Collider Detector at Fermilab (CDF) in a sample of Pp collisions at Js =1.8 TeV with an integrated luminosity of 19.3 pb . We find 12 events consistent with either two 8' bosons, or a 8' boson and at least one b jet. The probability that the measured yield is consistent with the background is 0.26%. Though the statistics are too limited to establish firmly the existence of the top quark, a natural interpretation of the excess is that it is due to tt production.Under this assumption, constrained fits to individual events yield a top quark mass of 174+ 10 -)) GeV/c . The tt production cross section is measured to be 13.9 -+)II pb. PACS numbers: 14.65.Ha, 13.85.Ni, 13.85.gk The standard model has enjoyed outstanding success, yet the top quark, which is required as the weak-isospin partner of the bottom quark, has remained unobserved. Direct searches at the Fermilab Tevatron have placed a 95%%uo confidence level lower limit of M&,~& 131 GeV/c [1]. Global fits to precision electroweak measurements yield a favored mass of M&,~= 177-+|I+ -I9 GeV/c [2]. One expects that, at Tevatron energies, most top quarks are produced in pairs. For M,o&~85 GeV/c, each top quark decays to a real 8' boson and a b quark.The observed event topology is then determined by the decay mode of the two H bosons. About 5k of the time 226 VOLUME 73, NUMBER 2 PHYSICAL REVIEW LETTERS 11 JULY 1994 both W bosons decay to ev or p v (the "dilepton mode"), giving two high-P~leptons with opposite charge, two b jets, and large missing transverse energy (k"7. ) from the undetected neutrinos [3]. In another 30% of the cases one W boson decays to ev or p v, and the other to a qq' pair (the "lepton+jets mode"). This final state includes a high-Pz charged lepton, k"z, and jets from the 8' and the two b quarks. The remaining 65% of the final states involve the hadronic decays of both W bosons, or the decay of one or both of the 8'bosons into r leptons. These channels have larger backgrounds and are not considered here. This analysis is based on a sample of pp collisions at vs =1. 8 TeV with an integrated luminosity of 19.3

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W e report a measurement o f the diffraction dissociation differential cross section d 2 u s~/ d M 2 d t for ?Sp + pX at f i = 546 and 1800 G e V , M 2 / s < 0.2 and 0 < -t < 0.4 G~v~. Our results are compared t o theoretical predictions and t o extrapolations from experimental results at lower energies. PACS number(s): 13.85.Hd, 12.40.Nn

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The phlogopite peridotite unit of the Finero Complex is a restitic largest in the Alps. The chromite is magnesian and locally harzburgite that records two metasomatic events. The first event is contains inclusions of Fe-Ni-Cu sulphide and platinum related to the intrusion of basaltic magma, which reacted with the group element minerals (Ferrario & Garuti, 1990). pyroxene of the host harzburgite to produce chromitite pods with dunite Chromitite forms well-defined bodies with modal chrohaloes. It also produced secondary clinopyroxene and amphibole in mite concentrations as high as 75%. The occurrences the harzburgite and enriched harzburgite in Na and the light rare were described by Roggiani (1948), Friedenreich (1956, earth elements. The second metasomatic event is related to the later Forbes et al. (1978) andSaager et al. (1982). intrusion of clinopyroxenitic dykes. During this event, water-richThe petrology of the Finero Complex is poorly unvapour penetrated the harzburgite along fractures and reacted with derstood. One reason is that the phlogopite peridotite, it to form phlogopite, thus enriching the rock in K. Chromitites host which makes up the core of the complex, exhibits anzircons that yield an age for the first metasomatic event of 207•9 + omalous petrographic and geochemical characteristics 1•7/−1•3 Ma, during which time extensional tectonics prevailed in indicative of metasomatism and of a multistage evolution the Southern Alps.