• Energy Research

We report first evidence for a fully reconstructed decay mode of the B_c^{\pm} meson in the channel B_c^{\pm} \to J/psi ��^{\pm}, with J/psi \to mu^+mu^-. The analysis is based on an integrated luminosity of 360 pb$^{-1} in p\bar{p} collisions at 1.96 TeV center of mass energy collected by the Collider Detector at Fermilab. We observe 14.6 \pm 4.6 signal events with a background of 7.1 \pm 0.9 events, and a fit to the J/psi pi^{\pm} mass spectrum yields a B_c^{\pm} mass of 6285.7 \pm 5.3(stat) \pm 1.2(syst) MeV/c^2. The probability of a peak of this magnitude occurring by random fluctuation in the search region is estimated as 0.012%. 7 pages, 3 figures. Version 3, accepted by PRL

A measurement is presented of the two-jet differential cross section d{sup 3}{sigma}/dE{sub T}d{eta}{sub 1}d{eta}{sub 2} at center of mass energy {radical}s=1800 GeV in p{bar p} collisions. The results are based on an integrated luminosity of 86 pb{sup {minus}1} collected during 1994 to 1995 by the CDF Collaboration at the Fermilab Tevatron collider. The differential cross section is measured as a function of the transverse energy E{sub T} of a jet in the pseudorapidity region 0.1{lt}{vert_bar}{eta}{sub 1}{vert_bar}{lt}0.7 for four different pseudorapidity bins of a second jet restricted to 0.1{lt}{vert_bar}{eta}{sub 2}{vert_bar}{lt}3.0. The results are compared with next-to-leading order QCD calculations determined using the CTEQ4 and MRST sets of parton distribution functions. None of the sets examined in this analysis provides a good description of the data.

We describe a general search for resonances decaying to a neutral e{mu} final state in p{bar p} collisions at a center-of-mass energy of 1.96 TeV. Using a data sample representing 344 pb{sup -1} of integrated luminosity recorded by the CDF II experiment, we compare Standard Model predictions with the number of observed events for invariant masses between 50 and 800 GeV/c{sup 2}. Finding no significant excess (5 events observed vs. 7.7 {+-} 0.8 expected for M{sub e{mu}} > 100 GeV/c{sup 2}), we set limits on sneutrino and Z' masses as functions of lepton family number violating couplings.

SVX4 is the new silicon strip readout IC designed to meet the increased radiation tolerance requirements for Run IIb at the Tevatron collider. Devices have been fabricated, tested, and approved for production. The SVX4 design is a technology migration of the SVX3D design currently in use by CDF. Whereas SVX3D was fabricated in a 0.8-/spl mu/m radiation-hard process, SVX4 was fabricated in a standard 0.25-/spl mu/m mixed-signal CMOS technology using the "radiation tolerant by design" transistor topologies devised by the CERN RD49 collaboration. The specific cell layouts include digital cells developed by the ATLAS Pixel group, and full-custom analog blocks. Unlike its predecessors, the new design also includes the necessary features required for generic use by both the CDF and D0 experiments at Fermilab. Performance of the IC includes >20 MRad total dose tolerance, and /spl sim/2000 e-rms equivalent input noise charge with 40-pF input capacitance, when sampled at 132-ns period with an 80-ns preamp risetime. At the nominal digitize/readout rate of 106/53 MHz, the 9 mm/spl times/6.3 mm die dissipates /spl sim/2 mW/channel average at 2.5 V. A review of typical operation, details of the design conversion process, and performance measurements are covered.