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Register a new userTransverse momentum cross section of $e^+e^-$ pairs in the $Z$-boson region from $pbar{p}$ collisions at $sqrt{s}=1.96$ TeV
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CDF Collaboration
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The transverse momentum cross section of $e^+e^-$ pairs in the $Z$-boson mass region of 66-116 GeV/$c^2$ is precisely measured using Run II data corresponding to 2.1 fb$^{-1}$ of integrated luminosity recorded by the Collider Detector at Fermilab. The cross section is compared with quantum chromodynamic calculations. One is a fixed-order perturbative calculation at ${cal O}(alpha_s^2)$, and the other combines perturbative predictions at high transverse momentum with the gluon resummation formalism at low transverse momentum. Comparisons of the measurement with calculations show reasonable agreement. The measurement is of sufficient precision to allow refinements in the understanding of the transverse momentum distribution.
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We report on a measurement of the $D^{+}$-meson production cross section as a function of transverse momentum ($p_T$) in proton-antiproton ($pbar{p}$) collisions at 1.96 TeV center-of-mass energy, using the full data set collected by the Collider Detector at Fermilab in Tevatron Run II and corresponding to 10 fb$^{-1}$ of integrated luminosity. We use $D^{+} to K^-pi^+pi^+$ decays fully reconstructed in the central rapidity region $|y|<1$ with transverse momentum down to 1.5 GeV/$c$, a range previously unexplored in $pbar{p}$ collisions. Inelastic $pbar{p}$-scattering events are selected online using minimally-biasing requirements followed by an optimized offline selection. The $K^-pi^+pi^+$ mass distribution is used to identify the $D^+$ signal, and the $D^+$ transverse impact-parameter distribution is used to separate prompt production, occurring directly in the hard scattering process, from secondary production from $b$-hadron decays. We obtain a prompt $D^+$ signal of 2950 candidates corresponding to a total cross section $sigma(D^+, 1.5 < p_T < 14.5~mbox{GeV/}c, |y|<1) = 71.9 pm 6.8 (mbox{stat}) pm 9.3 (mbox{syst})~mu$b. While the measured cross sections are consistent with theoretical estimates in each $p_T$ bin, the shape of the observed $p_T$ spectrum is softer than the expectation from quantum chromodynamics. The results are unique in $pbar{p}$ collisions and can improve the shape and uncertainties of future predictions.
We present a measurement of the inclusive jet cross section using the Run II cone algorithm and data collected by the D0 experiment in p pbar collisions at a center-of-mass energy sqrt(s)=1.96 TeV, corresponding to an integrated luminosity of 0.70 fb^(-1). The jet energy calibration and the method used to extract the inclusive jet cross section are described. We discuss the main uncertainties, which are dominated by the jet energy scale uncertainty. The results cover jet transverse momenta from 50 GeV to 600 GeV with jet rapidities in the range -2.4 to 2.4 and are compared to predictions using recent proton parton distribution functions. Studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented.
A measurement of the inclusive bottom jet cross section is presented for events containing a $Z$ boson in $pbar{p}$ collisions at $sqrt{s}=1.96$ TeV using the Collider Detector at Fermilab. $Z$ bosons are identified in their electron and muon decay modes, and $b$ jets with $E_T>20$ GeV and $|eta|<1.5$ are identified by reconstructing a secondary decay vertex. The measurement is based on an integrated luminosity of about 330 ${rm pb}^{-1}$. A cross section times branching ratio of $sigma (Z+b {rm jets}) times {cal B}(Z to ell^+ ell^-)= 0.93 pm 0.36$ pb is found, where ${cal B}(Zto ell^+ ell^-)$ is the branching ratio of the $Z$ boson or $gamma^*$ into a single flavor dilepton pair ($e$ or $mu$) in the mass range between 66 and 116 GeV$/c^2$. The ratio of $b$ jets to the total number of jets of any flavor in the $Z$ sample, within the same kinematic range as the $b$ jets, is $2.36 pm 0.92%$. Here, the uncertainties are the quadratic sum of statistical and systematic uncertainties. Predictions made with NLO QCD agree, within experimental and theoretical uncertainties, with these measurements.
Drell-Yan lepton pairs are produced in the process $pbar{p} rightarrow e^+e^- + X$ through an intermediate $gamma^*/Z$ boson. The lepton angular distributions are used to provide information on the electroweak-mixing parameter $sin^2theta_W$ via its observable effective-leptonic $sin^2theta_W$, or $sin^2theta^{lept}_{eff}$. A new method to infer $sin^2theta_W$, or equivalently, the W-boson mass M_W in the on-shell scheme, is developed and tested using a previous CDF Run II measurement of angular distributions from electron pairs in a sample corresponding to 2.1 fb-1 of integrated luminosity from $pbar{p}$ collisions at a center-of-momentum energy of 1.96 TeV. The value of $sin^2theta^{lept}_{eff}$ is found to be 0.2328 +- 0.0010. Within a specified context of the standard model, this results in $sin^2theta_W$ = 0.2246 +- 0.0009 which corresponds to a W-boson mass of 80.297 +- 0.048 GeV/c^2, in agreement with previous determinations in electron-position collisions and at the Tevatron collider.
We describe a measurement of the ratio of the cross sections times branching fractions of the $B_c^+$ meson in the decay mode $B_c^+ rightarrow J/psi mu u$ to the $B^+$ meson in the decay mode $B^+ rightarrow J/psi K^+$ in proton-antiproton collisions at center-of-mass energy $sqrt{s}=1.96$ TeV. The measurement is based on the complete CDF Run II data set, which comes from an integrated luminosity of $8.7,{rm fb}^{-1}$. The ratio of the production cross sections times branching fractions for $B_c^+$ and $B_c^+$ mesons with momentum transverse to the beam greater than $6~textrm{GeV}/c$ and rapidity magnitude smaller than 0.6 is $0.211pm 0.012~mbox{(stat)}^{+0.021}_{-0.020}~mbox{(syst)}$. Using the known $B^+ rightarrow J/psi K^+$ branching fraction, the known $B^+$ production cross section, and a selection of the predicted $B_c^+ rightarrow J/psi mu u$ branching fractions, the range for the total $B_c^+$ production cross section is estimated.
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