D. Benjamin

We establish the existence of the top quark using a $67{\mathrm{pb}}^{\ensuremath{-}1}$ data sample of $\overline{p}p$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ collected with the Collider Detector at Fermilab (CDF). Employing techniques similar to those we previously published, we observe a signal consistent with $t\overline{t}$ decay to $\mathrm{WWb}\overline{b}$, but inconsistent with the background prediction by $4.8\ensuremath{\sigma}$. Additional evidence for the top quark is provided by a peak in the reconstructed mass distribution. We measure the top quark mass to be $176\ifmmode\pm\else\textpm\fi{}8(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}10(\mathrm{syst})\mathrm{GeV}{/c}^{2}$, and the $t\overline{t}$ production cross section to be ${6.8}_{\ensuremath{-}2.4}^{+3.6}\mathrm{pb}$.

We present a new measurement of the inclusive and differential production cross sections of $J/\ensuremath{\psi}$ mesons and $b$ hadrons in proton-antiproton collisions at $\sqrt{s}=1960\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$. The data correspond to an integrated luminosity of $39.7\text{ }\text{ }{\mathrm{p}\mathrm{b}}^{\ensuremath{-}1}$ collected by the CDF run II detector. We find the integrated cross section for inclusive $J/\ensuremath{\psi}$ production for all transverse momenta from 0 to $20\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}/c$ in the rapidity range $|y|<0.6$ to be $4.08\ifmmode\pm\else\textpm\fi{}0.02(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}{)}_{\ensuremath{-}0.33}^{+0.36}(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\text{ }\text{ }\ensuremath{\mu}\mathrm{b}$. We separate the fraction of $J/\ensuremath{\psi}$ events from the decay of the long-lived $b$ hadrons using the lifetime distribution in all events with ${p}_{T}(J/\ensuremath{\psi})>1.25\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}/c$. We find the total cross section for $b$ hadrons, including both hadrons and antihadrons, decaying to $J/\ensuremath{\psi}$ with transverse momenta greater than $1.25\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}/c$ in the rapidity range $|y(J/\ensuremath{\psi})|<0.6$ is $0.330\ifmmode\pm\else\textpm\fi{}0.005(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}{)}_{\ensuremath{-}0.033}^{+0.036}(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\text{ }\text{ }\ensuremath{\mu}\mathrm{b}$. Using a Monte Carlo simulation of the decay kinematics of $b$ hadrons to all final states containing a $J/\ensuremath{\psi}$, we extract the first measurement of the total single $b$-hadron cross section down to zero transverse momentum at $\sqrt{s}=1960\text{ }\text{ }\mathrm{G}\mathrm{e}\mathrm{V}$. We find the total single $b$-hadron cross section integrated over all transverse momenta for $b$ hadrons in the rapidity range $|y|<0.6$ to be $17.6\ifmmode\pm\else\textpm\fi{}0.4(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}{)}_{\ensuremath{-}2.3}^{+2.5}(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\text{ }\text{ }\ensuremath{\mu}\mathrm{b}$.

We report the observation of a narrow state decaying into $J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and produced in $220\text{ }{\mathrm{p}\mathrm{b}}^{\ensuremath{-}1}$ of $\stackrel{\ifmmode \bar{}\else \={}\fi{}}{p}p$ collisions at $\sqrt{s}=1.96\text{ }\mathrm{T}\mathrm{e}\mathrm{V}$ in the CDF II experiment. We observe $730\ifmmode\pm\else\textpm\fi{}90$ decays. The mass is measured to be $3871.3\ifmmode\pm\else\textpm\fi{}0.7(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\ifmmode\pm\else\textpm\fi{}0.4(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})\text{ }\mathrm{M}\mathrm{e}\mathrm{V}/{c}^{2}$, with an observed width consistent with the detector resolution. This is in agreement with the recent observation by the Belle Collaboration of the $X(3872)$ meson.

The mass of the W boson, a mediator of the weak force between elementary particles, is tightly constrained by the symmetries of the standard model of particle physics. The Higgs boson was the last missing component of the model. After observation of the Higgs boson, a measurement of the W boson mass provides a stringent test of the model. We measure the W boson mass, M W , using data corresponding to 8.8 inverse femtobarns of integrated luminosity collected in proton-antiproton collisions at a 1.96 tera–electron volt center-of-mass energy with the CDF II detector at the Fermilab Tevatron collider. A sample of approximately 4 million W boson candidates is used to obtain <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>M</mml:mi> <mml:mi>W</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>80</mml:mn> <mml:mo>,</mml:mo> <mml:mn>433.5</mml:mn> <mml:mo>±</mml:mo> <mml:msub> <mml:mrow> <mml:mn>6.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mtext>stat</mml:mtext> </mml:mrow> </mml:msub> <mml:mo>±</mml:mo> <mml:msub> <mml:mrow> <mml:mn>6.9</mml:mn> </mml:mrow> <mml:mrow> <mml:mtext>syst</mml:mtext> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>80</mml:mn> <mml:mo>,</mml:mo> <mml:mn>433.5</mml:mn> <mml:mo>±</mml:mo> <mml:mn>9.4</mml:mn> <mml:mtext> MeV</mml:mtext> <mml:mo>/</mml:mo> <mml:msup> <mml:mi>c</mml:mi> <mml:mn>2</mml:mn> </mml:msup> </mml:mrow> </mml:math> , the precision of which exceeds that of all previous measurements combined (stat, statistical uncertainty; syst, systematic uncertainty; MeV, mega–electron volts; c , speed of light in a vacuum). This measurement is in significant tension with the standard model expectation.

We present the results of a search for the top quark in 19.3 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$ of p\ifmmode\bar\else\textasciimacron\fi{}p collisions at \ensuremath{\surd}s =1.8 TeV. The data were collected at the Fermilab Tevatron collider using the Collider Detector at Fermilab (CDF). The search includes standard model tt\ifmmode\bar\else\textasciimacron\fi{} decays to final states ee\ensuremath{\nu}\ensuremath{\nu}\ifmmode\bar\else\textasciimacron\fi{}, e\ensuremath{\mu}\ensuremath{\nu}\ensuremath{\nu}\ifmmode\bar\else\textasciimacron\fi{}, and \ensuremath{\mu}\ensuremath{\mu}\ensuremath{\nu}\ensuremath{\nu}\ifmmode\bar\else\textasciimacron\fi{} as well as e+\ensuremath{\nu}+jets or \ensuremath{\mu}+\ensuremath{\nu}+jets. In the (e,\ensuremath{\mu})+\ensuremath{\nu}+jets channel we search for b quarks from t decays via secondary vertex identification and via semileptonic decays of the b and cascade c quarks. In the dilepton final states we find two events with a background of 0.${56}_{\mathrm{\ensuremath{-}}0.13}^{+0.25}$ events. In the e,\ensuremath{\mu}+\ensuremath{\nu}+jets channel with a b identified via a secondary vertex, we find six events with a background of 2.3\ifmmode\pm\else\textpm\fi{}0.3. With a b identified via a semileptonic decay, we find seven events with a background of 3.1\ifmmode\pm\else\textpm\fi{}0.3. The secondary vertex and semileptonic-decay samples have three events in common. The probability that the observed yield is consistent with the background is estimated to be 0.26%. The statistics are too limited to firmly establish the existence of the top quark; however, a natural interpretation of the excess is that it is due to tt\ifmmode\bar\else\textasciimacron\fi{} production. We present several cross-checks. Some support this hypothesis; others do not. Under the assumption that the excess yield over background is due to tt\ifmmode\bar\else\textasciimacron\fi{}, constrained fitting on a subset of the events yields a mass of 174\ifmmode\pm\else\textpm\fi{}${10}_{\mathrm{\ensuremath{-}}12}^{+13}$ GeV/${\mathit{c}}^{2}$ for the top quark. The tt\ifmmode\bar\else\textasciimacron\fi{} cross section, using this top quark mass to compute the acceptance, is measured to be 13.${9}_{\mathrm{\ensuremath{-}}4.8}^{+6.1}$ pb.