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Register a new userSearch for First-Generation Scalar Leptoquarks in $bm{p bar{p}}$ collisions at $sqrt{s}$=1.96 TeV
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We report on a search for pair production of first-generation scalar leptoquarks ($LQ$) in $p bar{p}$ collisions at $sqrt{s}$=1.96 TeV using an integrated luminosity of 203 $pb^{-1}$ collected at the Fermilab Tevatron collider by the CDF experiment. We observe no evidence for $LQ$ production in the topologies arising from $LQ bar{LQ} to eqeq$ and $LQ bar{LQ} to eq u q$, and derive 95% C.L. upper limits on the $LQ$ production cross section. %as a function of $beta$, where $beta$ is the branching fraction for $LQ to eq$. The results are combined with those obtained from a separately reported CDF search in the topology arising from $LQbar{LQ} to u q u q$ and 95% C.L. lower limits on the LQ mass as a function of $beta = BR(LQ to eq) $ are derived. The limits are 236, 205 and 145 GeV/c$^2$ for $beta$ = 1, $beta$ = 0.5 and $beta$ = 0.1, respectively.
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We report on a search for charge-1/3 third-generation leptoquarks (LQ) produced in ppbar collisions at sqrt(s)=1.96 TeV using the D0 detector at Fermilab. Third generation leptoquarks are assumed to be produced in pairs and to decay to a tau neutrino and a b quark with branching fraction B. We place upper limits on sigma(ppbar->LQLQbar)*B^2 as a function of the leptoquark mass M_{LQ}. Assuming B=1, we exclude at the 95% confidence level third-generation scalar leptoquarks with M_{LQ} < 229 GeV.
We search for high-mass resonances decaying into Z boson pairs using data corresponding to 6 fb^-1 collected by the CDF experiment in pbar{p} collisions at sqrt{s}=1.96 TeV. The search is performed in three distinct final states: ZZ --> l^+l^-l^+l^-, ZZ --> l^+l^- u u, and ZZ --> l^+l^-jj. For a Randall-Sundrum graviton G*, the 95% CL upper limits on the production cross section times branching ratio to ZZ, sigma(pbar{p} --> G^* --> ZZ), vary between 0.26 pb and 0.045 pb in the mass range 300 < M_{G*} < 1000 GeV/c^2.
This Letter describes the current most precise measurement of the $WZ$ production cross section as well as limits on anomalous $WWZ$ couplings at a center-of-mass energy of 1.96 TeV in proton-antiproton collisions for the Collider Detector at Fermilab (CDF). $WZ$ candidates are reconstructed from decays containing three charged leptons and missing energy from a neutrino, where the charged leptons are either electrons or muons. Using data collected by the CDF II detector (7.1 fb$^{-1}$ of integrated luminosity), 63 candidate events are observed with the expected background contributing $8 pm 1$ events. The measured total cross section $sigma (p bar p to WZ) = 3.93_{-0.53}^{+0.60}(text{stat})_{-0.46}^{+0.59}(text{syst}) $ pb is in good agreement with the standard model prediction of $3.50pm 0.21$. The same sample is used to set limits on anomalous $WWZ$ couplings.
The angular distributions of muons from Upsilon(1S,2S,3S) to mu+mu- decays are measured using data from proton anti-proton collisions at sqrt(s)=1.96 TeV corresponding to an integrated luminosity of 6.7 /fb and collected with the CDF II detector at the Fermilab Tevatron. This analysis is the first to report the full angular distributions as functions of transverse momentum pT for the Upsilon mesons in both the Collins-Soper and s-channel helicity frames. This is also the first measurement of spin alignment of Upsilon(3S) mesons. Within the kinematic range of Upsilon rapidity |y|<0.6 and pT up to 40 GeV/c, the angular distributions are found to be nearly isotropic.
A measurement of vector boson ($V$) production in conjunction with a $D^{*}(2010)^+$ meson is presented. Using a data sample corresponding to $9.7, {rm fb}^{-1}$ of ^Mproton-antiproton collisions at center-of-mass energy $sqrt{s}=1.96rm~ TeV$ produced by the Fermilab Tevatron, we reconstruct $V+D^{*+}$ samples with the CDF~II detector. The $D^{*+}$ is fully reconstructed in the $D^{*}(2010)^+ rightarrow D^{0}(to K^-pi^+)pi^+$ decay mode. This technique is sensitive to the associated production of vector boson plus charm or bottom mesons. We measure the ratio of production cross sections $sigma(W+D^{*})/sigma(W)$ = $[1.75pm 0.13 {rm (stat)}pm 0.09 {rm (syst)}]% $ and $sigma(Z+D^{*})/sigma(Z)$ = $[1.5pm 0.4 {rm (stat)} pm 0.2 {rm (syst)}]% $ and perform a differential measurement of $dsigma(W+D^{*})/dp_T(D^{*})$. Event properties are utilized to determine the fraction of $V+D^{*}(2010)^+$ events originating from different production processes. The results are in agreement with the predictions obtained with the {sc pythia} program, limiting possible contribution from non-standard-model physics processes.
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