arXiv subjects

CDF Collaboration

Publications and source records attributed to CDF Collaboration.

At least 307 records · Page 17Linked to original sources

arXiv2005

First Evidence for $B_s^0 \to ϕϕ$ Decay and Measurements of Branching Ratio and $A_{CP}$ for $B^+ \to ϕK^+$

We present the first evidence of charmless decays of the $B_s^0$ meson, the decay \phiphi, and a measurement of the Branching Ratio $\BR(\phiphi)$ using $180 {\rm pb}^{-1}$ of data collected by the \cdfii experiment at the Fermilab Tevatron collider. In addition, the BR and direct CP asymmetry for the \phik\ decay are measured. We obtain: $\BR (\phiphi) = (14 \ase{6}{5}(stat.) \pm 6(syst.)) \times 10^{-6}$, $\BR (\phik) = (7.6 \pm 1.3(stat.) \pm 0.6(syst.)) \times 10^{-6}$, and $\ACP(\phik) = -0.07 \pm 0.17 (stat.) \ase{0.03}{0.02} (syst.)$. Both decays are governed in the Standard Model by second order (penguin) $b \myto s\bar{s}s$ amplitudes.

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arXiv2005

Search for ZZ and ZW Production in ppbar Collisions at sqrt(s) = 1.96 TeV

We present a search for ZZ and ZW vector boson pair production in ppbar collisions at sqrt(s) = 1.96 TeV using the leptonic decay channels ZZ --> ll nu nu, ZZ --> l l l' l' and ZW --> l l l' nu. In a data sample corresponding to an integrated luminosity of 194 pb-1 collected with the Collider Detector at Fermilab, 3 candidate events are found with an expected background of 1.0 +/- 0.2 events. We set a 95% confidence level upper limit of 15.2 pb on the cross section for ZZ plus ZW production, compared to the standard model prediction of 5.0 +/- 0.4 pb.

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arXiv2005

Measurements of Bottom Anti-Bottom Azimuthal Production Correlations in Proton-Antiproton Collisions at s**(1/2)= 1.8 TeV

We have measured the azimuthal angular correlation of bottom anti-bottom production, using 86.5 pb-1 of data collected by Collider Detector at Fermilab (CDF) in proton anti-proton collisions at sqrt{s}=1.8 TeV during 1994-1995. In high-energy p-pbar collisions, such as at the Tevatron, bottom anti-bottom production can be schematically categorized into three mechanisms. The leading-order (LO) process is ``flavor creation,'' where both the bottom and anti-bottom quarks substantially participate in the hard scattering and result in a distinct back-to-back signal in final state. The ``flavor excitation'' and the ``gluon splitting'' processes, which appear at next-leading-order (NLO), are known to make a comparable contribution to total bottom anti-bottom cross section, while providing very different opening angle distributions from the LO process. An azimuthal opening angle between bottom and anti-bottom, Delta phi, has been used for the correlation measurement to probe the interaction creating bottom anti-bottom pairs. The Delta phi distribution has been obtained from two different methods. One method measures the Delta phi between bottom hadrons using events with two reconstructed secondary vertex tags. The other method uses b-bbar --> (J/psi X)(l X') events, where the charged lepton (l) is an electron or a muon, to measure Delta phi between bottom quarks. The bottom anti-bottom purity is determined as a function of Delta phi by fitting the decay length of the J/psi and the impact parameter of the lepton. Both methods quantify the contribution from higher-order production mechanisms by the fraction of the b-bbar pairs produced in the same azimuthal hemisphere, f_toward. The measured f_toward values are consistent with both parton shower Monte Carlo and NLO QCD predictions.

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arXiv2005

Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s}=1.96 TeV using Lepton + Jets Events with Secondary Vertex b-tagging

We present a measurement of the ttbar production cross section using events with one charged lepton and jets from ppbar collisions at a center-of-mass energy of 1.96 TeV. In these events, heavy flavor quarks from top quark decay are identified with a secondary vertex tagging algorithm. From 162 pb-1 of data collected by the Collider Detector at Fermilab, a total of 48 candidate events are selected, where 13.5 +- 1.8 events are expected from background contributions. We measure a ttbar production cross section of 5.6^{+1.2}_{-1.1} (stat.) ^{+0.9}_{0.6} (syst.) pb.

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arXiv2005

Measurement of Partial Widths and Search for Direct CP Violation in $D^0$ Meson Decays to $K^-K^+$ and $π^-π^+$

We present a measurement of relative partial widths and decay rate CP asymmetries in $K^-K^+$ and $π^-π^+$ decays of $\Do$ mesons produced in $p\bar{p}$ collisions at $\sqrt{s} = 1.96 \TeV$. We use a sample of $2\times10^5$ $D^{\ast+}\myto D^0π^+$ (and charge conjugate) decays with the $D^0$ decaying to $K^-π^+$, $K^-K^+$, and $π^-π^+$, corresponding to $123 {\rm pb}^{-1}$ of data collected by the Collider Detector at Fermilab II experiment at the Fermilab Tevatron collider. No significant direct CP violation is observed. We measure $\KKtokpi = 0.0992 \pm 0.0011 \pm 0.0012$, $\PIpitokpi = 0.03594 \pm 0.00054 \pm 0.00040$, $A_{CP}(K^-K^+) = (2.0 \pm 1.2 \pm 0.6) %$, and $A_{CP}(π^-π^+) = (1.0 \pm 1.3 \pm 0.6) %$, where, in all cases, the first uncertainty is statistical and the second is systematic.

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arXiv2005

Measurement of the Moments of the Hadronic Invariant Mass Distribution in Semileptonic B Decays

Using 180 pb^-1 of data collected with the CDF II detector at the Tevatron, we measure the first two moments of the hadronic invariant mass-squared distribution in charmed semileptonic B decays. From these we determine the non-perturbative Heavy Quark Effective Theory parameters Lambda and lambda_1, used to relate the B meson semileptonic branching ratio to the CKM matrix element |V_cb|. For a minimum lepton momentum of 0.7 GeV/c in the B rest frame me measure the first two moments of the D** --> D(*) pi component to be = (5.83 +/- 0.16(stat) +/- 0.08(syst)) GeV^2, <(m^2_D** - )^2> = (1.30 +/- 0.69(stat) +/- 0.22(syst)) GeV^4. Combining these with the discrete mass terms from the D and D* mesons, we find the total moments to be - mbar_D^2 = (0.467 +/- 0.038_(stat) +/- 0.068(syst)) GeV^2, <(M^2_Xc - )^2> = (1.05 +/- 0.26(stat) +/- 0.13(syst)) GeV^4, where mbar_D is the spin-averaged D mass. The systematic error is dominated by the uncertainties in the world-average branching ratios used to combine the D, D* and D** contributions. The analysis makes no assumptions about the shape or resonant structure of the D** --> D(*) pi invariant mass distribution.

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arXiv2005

Search for Anomalous Production of Diphoton Events with Missing Transverse Energy at CDF and Limits on Gauge-Mediated Supersymmetry-Breaking Models

We present the results of a search for anomalous production of diphoton events with large missing transverse energy using the Collider Detector at Fermilab. In 202 $\invpb$ of $\ppbar$ collisions at $\sqrt{s}=1.96$ TeV we observe no candidate events, with an expected standard model background of $0.27\pm0.07({\rm stat})\pm0.10({\rm syst})$ events. The results exclude a lightest chargino of mass less than 167 GeV/$c^2$, and lightest neutralino of mass less than 93 GeV/$c^2$ at 95% C.L. in a gauge--mediated supersymmetry-- breaking model with a light gravitino.

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arXiv2005

Measurement of $Wγ$ and $Zγ$ Production in $p\bar{p}$ Collisions at $\sqrt{s}$ = 1.96 TeV

The Standard Model predictions for $Wγ$ and $Zγ$ production are tested using an integrated luminosity of 200 pb$^{-1}$ of \ppbar collision data collected at the Collider Detector at Fermilab. The cross sections are measured selecting leptonic decays of the $W$ and $Z$ bosons, and photons with transverse energy $E_T>7$ GeV that are well separated from leptons. The production cross sections and kinematic distributions for the $Wγ$ and $Zγ$ are compared to SM predictions.

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arXiv2005

Search for electroweak single top quark production in ppbar collisions at sqrt{s}=1.96 TeV

We report on a search for Standard Model t-channel and s-channel single top quark production in ppbar collisions at a center of mass energy of 1.96 TeV. We use a data sample corresponding to 162 pb^{-1} recorded by the upgraded Collider Detector at Fermilab. We find no significant evidence for electroweak top quark production and set upper limits at the 95% confidence level on the production cross section, consistent with the Standard Model: 10.1 pb for the t-channel, 13.6 pb for the s-channel and 17.8 pb for the combined cross section of t- and s-channel.

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arXiv2005

Measurement of the W+W- Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Dilepton Events

We present a measurement of the W+W- production cross section using 184/pb of ppbar collisions at a center-of-mass energy of 1.96 TeV collected with the Collider Detector at Fermilab. Using the dilepton decay channel W+W- -> l+l-vvbar, where the charged leptons can be either electrons or muons, we find 17 candidate events compared to an expected background of 5.0+2.2-0.8 events. The resulting W+W- production cross section measurement of sigma(ppbar -> W+W-) = 14.6 +5.8 -5.1 (stat) +1.8 -3.0 (syst) +-0.9 (lum) pb agrees well with the Standard Model expectation.

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arXiv2004

Measurement of the J/Psi Meson and b-Hadron Production Cross Sections in ppbar Collisions at sqrt s = 1960 GeV

We present a new measurement of the inclusive and differential production cross sections of $J/ψ$ mesons and $b$-hadrons in proton-antiproton collisions at $\sqrt{s}=1960$ GeV. The data correspond to an integrated luminosity of 39.7 pb$^{-1}$ collected by the CDF Run II detector. We find the integrated cross section for inclusive $J/ψ$ production for all transverse momenta from 0 to 20 GeV/$c$ in the rapidity range $|y|<0.6$ to be $4.08 \pm 0.02 (stat)^{+0.36}_{-0.33} (syst) μ{\rm b}$. We separate the fraction of $J/ψ$ events from the decay of the long-lived $b$-hadrons using the lifetime distribution in all events with $p_T(J/ψ) > 1.25$ GeV/$c$. We find the total cross section for $b$-hadrons, including both hadrons and anti-hadrons, decaying to $J/ψ$ with transverse momenta greater than 1.25 GeV/$c$ in the rapidity range $|y(J/ψ)|<0.6$, is $ 0.330 \pm 0.005 (stat) ^{+0.036}_{-0.033} (syst) ~μ{\rm b}$. Using a Monte Carlo simulation of the decay kinematics of $b$-hadrons to all final states containing a $J/ψ$, we extract the first measurement of the total single $b$-hadron cross section down to zero transverse momentum at $\sqrt{s}=1960$ GeV. 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 \pm 0.4 (stat)^{+2.5}_{-2.3} (syst) μ{\rm b}$.

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arXiv2004

Measurement of the W Boson Polarization in Top Decay at CDF at s**(1/2) = 1.8 TeV

The polarization of the $W$ boson in $t \to W b$ decay is unambiguously predicted by the Standard Model of weak interactions and is a powerful test of our understanding of the $tbW$ vertex. The subsequent $W \to l ν$ decay serves as a polarimeter for the $W$, and the invariant mass of the lepton and $b$ quark in top decay provides a measurement of the $W$ decay angle. In this paper we present a measurement of the decay rate of the W produced from the decay of the top quark in the hypothesis of V+A structure of the tWb vertex. We find no evidence for the non-standard V+A vertex and set a limit on $f_{V+A}$ $<$ 0.80 @ 95% confidence level. By combining this result with a complementary observable in the same data, we assign a limit of $f_{V+A}$ $<$ 0.61 @ 95% CL.

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arXiv2004

Measurement of the Forward-Backward Charge Asymmetry of Electron-Positron Pairs in Proton anti-Proton Collisions at s**(1/2)=1.96-TeV

We present a measurement of the mass dependence of the forward-backward charge asymmetry (A_{FB}) for electron-positron pairs produced via an intermediate Z/gamma with mass Mee > 40 GeV/c**(2). We study the constraints on the Z-quark couplings imposed by our measurement. We analyze an integrated luminosity of 72 pb-1 collected by the CDF II detector in proton anti-proton collisions at s**(1/2) = 1.96 TeV at the Fermilab Tevatron. A comparison of the uncorrected A_{FB} between data and Standard Model Monte Carlo gives good agreement with a chi^2/DOF of 15.7/15. The couplings measurements are also consistent with Standard Model predictions.

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arXiv2004

Search for Scalar Leptoquark Pairs Decaying to $ν\bar νq \bar q$ in \ppbar Collisions at $\sqrt {s} = 1.96$ TeV

We report on a search for the pair production of scalar leptoquarks, $LQ$, using 191 pb$^{-1}$ of proton-antiproton collision data recorded by the CDF experiment during Run II of the Tevatron. The leptoquarks are sought via their decay into a neutrino and quark yielding missing transverse energy and several jets of large transverse energy. No evidence for leptoquark production is observed, and limits are set on $σ(p\bar p\to LQ\bar{LQ} X \to ν\barνq\bar q X)$. Using a next-to-leading order theoretical prediction of the cross section for scalar leptoquark production, we exclude first-generation leptoquarks in the mass interval 78 to 117 GeV$/c^2$ at the 95% confidence level for BR($LQ\to νq)=100%$.

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arXiv2004

First Measurements of Inclusive W and Z Cross Sections from Run II of the Tevatron Collider

We report the first measurements of inclusive W and Z cross sections times leptonic branching ratios for p-pbar collisions at $\sqrt{s} = 1.96$ TeV, based on their decays to electrons and muons. The data correspond to an integrated luminosity of 72 pb-1 recorded with the CDF detector at the Fermilab Tevatron. We test e-mu universality in W decays, and we measure the ratio of leptonic W and Z rates from which the leptonic branching fraction $B(W\goto\ellν)$ can be extracted as well as an indirect value for the total width of the W and the CKM matrix element, Vcs.

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arXiv2004

Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s) = 1.96 TeV using Dilepton Events

We report a measurement of the ttbar production cross section using dilepton events with jets and missing transverse energy in ppbar collisions at a center-of-mass energy of 1.96 TeV. Using a 197 +/- 12 pb-1 data sample recorded by the upgraded Collider Detector at Fermilab, we use two complementary techniques to select candidate events. We compare the number of observed events and selected kinematical distributions with the predictions of the Standard Model and find good agreement. The combined result of the two techniques yields a ttbar production cross section of 7.0 +2.4/-2.1(stat.) +1.6/-1.1(syst.) +/- 0.4(lum.) pb.

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arXiv2004

Inclusive Search for Anomalous Production of High-pT Like-Sign Lepton Pairs in Proton-Antiproton Collisions at sqrt{s}=1.8 TeV

We report on a search for anomalous production of events with at least two charged, isolated, like-sign leptons with pT > 11 GeV/c using a 107 pb^-1 sample of 1.8 TeV ppbar collisions collected by the CDF detector. We define a signal region containing low background from Standard Model processes. To avoid bias, we fix the final cuts before examining the event yield in the signal region using control regions to test the Monte Carlo predictions. We observe no events in the signal region, consistent with an expectation of 0.63^(+0.84)_(-0.07) events. We present 95% confidence level limits on new physics processes in both a signature-based context as well as within a representative minimal supergravity (tanbeta = 3) model.

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arXiv2004

Search for Bs->mu+mu- and Bd->mu+mu- Decays in ppbar Collisions at sqrt(s)=1.96 TeV

We report on a search for Bs->mu+mu- and Bd->mu+mu- decays in ppbar collisions at sqrt(s)=1.96 TeV using 171 pb-1 of data collected by the CDF II experiment at the Fermilab Tevatron Collider. The decay rates of these rare processes are sensitive to contributions from physics beyond the Standard Model. One event survives all our selection requirements,consistent with the background expectation. We derive branching ratio limits of BR(Bs->mu+mu-) < 5.8 x 10^-7 and BR(Bd->mu+mu-) < 1.5 x 10^-7 at 90% confidence level.

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