Search

Using a silicon-microstrip detector array to identify secondary vertices, we have observed {ital b}{r_arrow}{ital J}/{psi}{r_arrow}{mu}{sup +}{mu}{sup {minus}} decays in 800 GeV/{ital c} proton-gold interactions. The doubly differential cross section for {ital J}/{psi} mesons originating from {ital b}-quark decays, assuming linear dependence on nucleon number, is {ital d}{sup 2}{sigma}/{ital dx}{sub {ital Fdp}}{sup 2}{sub {ital T}}=107{plus_minus}28{plus_minus}19/nucleon at {ital x}{sub {ital F}}=0.05 and {ital p}{sub {ital T}}=1GeV/{ital c}. This measurement is compared to next-to-leading-order QCD predictions. The integrated {ital b}-quark production cross section, obtained by extrapolation over all {ital x}{sub {ital F}} and {ital p}{sub {ital T}}, is {sigma}({ital pN}{r_arrow}{ital bb}{ovr bar}+{ital X})=5.7{plus_minus}1.5{plus_minus}1.3 nb/nucleon.

The differential cross sections do/dxF for J/G produced inclusively in 800 GeV/c p-Cn and pBe collisions have been measured in the kinematic range 0.30 5 IF < 0.95 through the decay mode J/G + p+p-. They are compared with the predictions of the semilocal duality model for several sets of parton density functions. No evidence for a suggested intrinsic charm contribution to the cross section is observed. The ratio of the differential cross sections for Cu and Be targets confirms the suppression of J/$ production in heavy nuclei at large ZF.

Results of a search for the three neutral charm decays, D0 -> mu e, D0 -> mu mu, and D0 -> e e, are presented. This study was based on data collected in Experiment 789 at the Fermi National Accelerator Laboratory using 800 GeV/c proton-Au and proton-Be interactions. No evidence is found for any of the decays. Upper limits on the branching ratios, at the 90% confidence level, are obtained., 28 pages, 18 figures. Submitted to Physical Review D

We present a measurement of the W-to-Be per-nucleon cross-section ratio, ${\mathit{R}}_{\mathrm{W}/\mathrm{B}\mathrm{e}}$, for single hadrons and for opposite-sign hadron pairs produced in p-A collisions at \ensuremath{\surd}s=38.8 GeV. The data fill in regions of intermediate transverse momentum and dihadron mass that previously have revealed cross-section enhancements for scattering from nuclear targets. When combined with previous measurements, the new results help delineate the dependence of nuclear effects on the kinematic variables ${\mathit{p}}_{\mathit{t}}$, m, and \ensuremath{\surd}s. Both the single-hadron and hadron-pair enhancements in ${\mathit{R}}_{\mathrm{W}/\mathrm{B}\mathrm{e}}$ seen at intermediate values of ${\mathit{p}}_{\mathit{t}}$ and mass decrease with increasing \ensuremath{\surd}s, consistent with a multiple-scattering model of parton scattering. \textcopyright{} 1996 The American Physical Society.

With a data sample containing 1.1{times}10{sup 5} {ital J}/{psi}{r_arrow}{mu}{sup +}{mu}{sup {minus}} decays reconstructed with 16 MeV/{ital c}{sup 2} rms mass resolution, we have measured the differential cross sections versus Feynman-{ital x}, rapidity, and {ital p}{sub {ital T}} for the production of {ital J}/{psi} and {psi}{prime} in 800 GeV/{ital c} {ital p}-Au collisions. Our results are compared with leading-order QCD predictions and with previous measurements. While the shapes of the cross sections are in qualitative agreement with QCD predictions, the magnitudes disagree by factors of 7 ({ital J}/{psi}) and 25 ({psi}{prime}). Assuming an appropriate form for the differential cross sections in regions not measured we derive a total {ital J}/{psi} production cross section {sigma}({ital p}+{ital N}{r_arrow}{ital J}/{psi}+{ital X})=442{plus_minus}2{plus_minus}88 nb/nucleon and a (model-dependent) total {psi}{prime} cross secton {sigma}({ital p}+{ital N}{r_arrow}{psi}{prime}+{ital X})=75{plus_minus}5{plus_minus}22 nb/nucleon. For {ital J}/{psi} produced at central rapidity, {ital d}{sigma}({ital p}+{ital N}{r_arrow}{ital J}/{psi}+{ital X})/{ital dy}{vert_bar}{sub {ital y}=0}=230{plus_minus}5{plus_minus}46 nb/nucleon.

Fermilab experiment 789 studies low‐multiplicity decays of neutral D and B mesons in a high‐rate fixed‐target environment. Preliminary results from the 1991 run are presented.