arXiv subjects

CDF Collaboration

Publications and source records attributed to CDF Collaboration.

At least 325 records · Page 18Linked to original sources

arXiv2004

Search for Doubly-Charged Higgs Bosons Decaying to Dileptons in ppbar Collisions at sqrt(s)=1.96 TeV

We present the results of a search for doubly-charged Higgs bosons (H+/-+/-) decaying to dileptons using ~240/pb of ppbar collision data collected by the CDF II experiment at the Fermilab Tevatron. In our search region, given by same-sign dilepton mass m_ll' > 80 GeV/c^2 (100 GeV/c^2 for dielectron channel), we observe no evidence for doubly-charged Higgs production. We set limits on sigma (ppbar --> H++H-- --> l+l+l-l-) as a function of the mass of the doubly-charged Higgs boson and the chirality of its couplings. Assuming exclusive same-sign dilepton decays, we derive lower mass limits on H+/-+/-_L of 133 GeV/c^2, 136 GeV/c^2, and 115 GeV/c^2 in the ee, mu mu, and e mu channels, respectively, and a lower mass limit of 113 GeV/c^2 on H+/-+/-_R in the mu mu channel, all at the 95% confidence level.

hep-ex↗

arXiv2004

The Underlying Event in Hard Interactions at the Tevatron pbarp Collider

For comparison of inclusive jet cross sections measured at hadron-hadron colliders to next-to-leading order (NLO) parton-level calculations, the energy deposited in the jet cone by spectator parton interactions must first be subtracted. The assumption made at the Tevatron is that the spectator parton interaction energy is similar to the ambient level measured in minimum bias events. In this paper, we test this assumption by measuring the ambient charged track momentum in events containing large transverse energy jets at $\sqrt{s}=1800$ GeV and $\sqrt{s}=630$ GeV and comparing this ambient momentum with that observed both in minimum bias events and with that predicted by two Monte Carlo models. Two cones in $η$--$ϕ$ space are defined, at the same pseudo-rapidity, $η$, as the jet with the highest transverse energy ($E_T^{(1)}$), and at $\pm 90^o$ in the azimuthal direction, $ϕ$. The total charged track momentum inside each of the two cones is measured. The minimum momentum in the two cones is almost independent of $E_T^{(1)}$ and is similar to the momentum observed in minimum bias events, whereas the maximum momentum increases roughly linearly with the jet $E_T^{(1)}$ over most of the measured range. This study will help improve the precision of comparisons of jet cross section data and NLO perturbative QCD predictions. %this is new The distribution of the sum of the track momenta in the two cones is also examined for five different $E_T^{(1)}$ bins. The HERWIG and PYTHIA Monte Carlos are reasonably successful in describing the data, but neither can describe completely all of the event properties.

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arXiv2003

Search for the Flavor-Changing Neutral Current Decay D^0\toμ^+μ^- in p\bar{p} Collisions at \sqrt{s}=1.96 TeV

We report on a search for the flavor-changing neutral current decay D^0\toμ^+μ^- in p\bar{p} collisions at \sqrt{s}=1.96 TeV using 65\ipb of data collected by the CDF II experiment at the Fermilab Tevatron Collider. A displaced-track trigger selects long-lived D^0 candidates in the D^0\toμ^+μ^- search channel, the kinematically similar D^0\toπ^+π^- channel used for normalization, the Cabbibo-favored D^0\to K^+π^- channel used to optimize the selection criteria in an unbiased manner, and their charge conjugates. Finding no signal events in the D^0\toμ^+μ^- search window, we set an upper limit on the branching fraction {\cal B}(D^0\toμ^+μ^-)\leq 2.5E-6 (3.3E-6) at the 90% (95%) confidence level.

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arXiv2003

The CDF Silicon Vertex Trigger

The CDF experiment's Silicon Vertex Trigger is a system of 150 custom 9U VME boards that reconstructs axial tracks in the CDF silicon strip detector in a 15 microsecond pipeline. SVT's 35 micron impact parameter resolution enables CDF's Level 2 trigger to distinguish primary and secondary particles, and hence to collect large samples of hadronic bottom and charm decays. We review some of SVT's key design features. Speed is achieved with custom VLSI pattern recognition, linearized track fitting, pipelining, and parallel processing. Testing and reliability are aided by built-in logic state analysis and test-data sourcing at each board's input and output, a common inter-board data link, and a universal "Merger" board for data fan-in/fan-out. Speed and adaptability are enhanced by use of modern FPGAs.

physics.ins-det↗

arXiv2003

Search For Pair Production of Scalar Top Quarks in R-parity Violating Decay Modes in ppbar Collisions at sqrt{s} = 1.8 TeV

We present the results of a search for pair production of scalar top quarks in an R-parity violating supersymmetry scenario in 106 pb-1 of ppbar collisions at $\sqrt{s} = 1.8$ TeV collected by the Collider Detector at Fermilab. In this mode each scalar top quark decays into a tau lepton and a b quark. We search for events with two tau's, one decaying leptonically (e or mu) and one decaying hadronically, and two jets. No candidate events pass our final selection criteria. We set a 95% confidence level lower limit on the scalar top quark mass at 122 GeV/c2 for Br (stop-> tau + b) = 1.

hep-ex↗

arXiv2003

Search for the Supersymmetric Partner of the Top Quark in Dilepton Events from p-pbar Collisions at 1.8 TeV

We have searched for the supersymmetric partner of the top quark (stop) in 107 pb^{-1} of p-pbar collisions at \sqrt{s}= 1.8 TeV collected by the Collider Detector at Fermilab (CDF). Within the framework of the Minimal Supersymmetric extension of the Standard Model (MSSM) each of the pair-produced stops is assumed to decay into a lepton, bottom quark and supersymmetric neutrino. Such a scenario would give rise to events with two leptons, two hadronic jets, and a substantial imbalance of transverse energy. No evidence of such a stop signal has been found. We calculate a 95% confidence level (C.L.) upper limit on the stop production cross section, which excludes stop masses in the region (80<m_{\stop}<135 GeV/c^2) in the mass plane of stop versus sneutrino.

hep-ex↗

arXiv2002

Limits on Extra Dimensions and New Particle Production in the Exclusive Photon and Missing Energy Signature in p pbar Collisions at sqrt(s) = 1.8 TeV

The exclusive gamma-met signal has a small standard model cross-section and is thus a good channel in which to look for signs of new physics. This signature is predicted by models with a superlight gravitino or with large extra spatial dimensions. We search for such signals at the CDF detector at the Tevatron, using 87 pb^-1 of data at sqrt(s) = 1.8 TeV, and extract 95% C.L. limits on these processes. A limit of 221 GeV is set on the scale |F|^{1/2} in supersymmetry models. For 4, 6, and 8 extra dimensions, limits on the fundamental mass scale M_D of 549, 581, and 602 GeV, respectively, are found. We also specify a `pseudo-model-independent' method of comparing the results to theoretical predictions.

hep-ex↗

arXiv2002

Search for New Heavy Particles in the WZ Final State in Proton Anti-Proton Collisions at Sqrt{s} = 1.8 TeV

We present a search for new heavy particles, $X$, which decay via $X rightarrow WZ \to eν+jj$ in $p{\bar p}$ collisions at $\sqrt{s} = 1.8$ TeV. No evidence is found for production of $X$ in 110 pb$^{-1}$ of data collected by the Collider Detector at Fermilab. Limits are set at the 95% C.L. on the mass and the production of new heavy charged vector bosons which decay via $W'\to WZ$ in extended gauge models as a function of the width, $Gamma (W')$, and mixing factor between the $W'$ and the Standard Model $W$ bosons.

hep-ex↗

arXiv2002

Comparison of the Isolated Direct Photon Cross Sections in $p \bar p$ Collisions at $\sqrt{s}=1.8$ TeV and $\sqrt{s}=0.63$ TeV

We have measured the cross sections $d^2σ/dP_T dη$ for production of isolated direct photons in \pbarp collisions at two different center-of-mass energies, 1.8 TeV and 0.63 TeV, using the Collider Detector at Fermilab (CDF). The normalization of both data sets agree with the predictions of Quantum Chromodynamics (QCD) for photon transverse momentum ($P_T$) of 25 GeV/c, but the shapes versus photon $P_T$ do not. These shape differences lead to a significant disagreement in the ratio of cross sections in the scaling variable $x_T (\equiv 2P_T/\sqrt{s}$). This disagreement in the $x_T$ ratio is difficult to explain with conventional theoretical uncertainties such as scale dependence and parton distribution parameterizations.

hep-ex↗

arXiv2001

Search for Single-Top-Quark Production in p-pbar Collisions at sqrt(s)=1.8 TeV

We search for standard model single-top-quark production in the W-gluon fusion and W* channels using 106 pb^-1 of data from p-pbar collisions at sqrt(s)=1.8 TeV collected with the Collider Detector at Fermilab. We set an upper limit at 95% C.L. on the combined W-gluon fusion and W* single-top cross section of 14 pb, roughly six times larger than the standard model prediction. Separate 95% C.L. upper limits in the W-gluon fusion and W* channels are also determined and are found to be 13 and 18 pb, respectively.

hep-ex↗

arXiv2001

Search for New Physics in Photon-Lepton Events in Proton-Antiproton Collisions at sqrt(s) = 1.8 TeV

We present the results of a search in proton-antiproton collisions at sqrt(s) = 1.8 TeV for anomalous production of events containing a photon with large transverse energy and a lepton (e or mu) with large transverse energy, using 86 pb^{-1} of data collected with the Collider Detector at Fermilab during the 1994-95 collider run at the Fermilab Tevatron. The presence of large missing transverse energy, additional photons, or additional leptons in these events is also analyzed. The results are consistent with standard model expectations, with the possible exception of photon-lepton events with large missing transverse energy, for which the observed total is 16 events and the expected mean total is 7.6+/-0.7 events.

hep-ex↗

arXiv2001

Searches for New Physics in Events with a Photon and b-quark Jet at CDF

We have searched for evidence of physics beyond the standard model in events that include an energetic photon and an energetic b-quark jet, produced in 85pb of ppbar collisions at 1.8 TeV at the Tevatron Collider at Fermilab. This signature, containing at least one gauge boson and a third-generation quark, could arise in the production and decay of a pair of new particles, such as those predicted by Supersymmetry, leading to a production rate exceeding standard model predictions. We also search these events for anomalous production of missing transverse energy, additional jets and leptons (e, mu and tau), and additional b quarks. We find no evidence for any anomalous production of gamma-b or gamma-b+X events. We present limits on two supersymmetric models: a model where the photon is produced in the decay chi2->gamma chi1, and a model where the photon is produced in the neutralino decay into the Gravitino LSP, chi1 -> gamma G. We also present our limits in a model-independent form and test methods of applying model-independent limits.

hep-ex↗

arXiv2001

A Study of B0 -> J/psi K(*)0 pi+ pi- Decays with the Collider Detector at Fermilab

We report a study of the decays B0 -> J/psi K(*)0 pi+ pi-, which involve the creation of a u u-bar or d d-bar quark pair in addition to a b-bar -> c-bar(c s-bar) decay. The data sample consists of 110 1/pb of p p-bar collisions at sqrt{s} = 1.8 TeV collected by the CDF detector at the Fermilab Tevatron collider during 1992-1995. We measure the branching ratios to be BR(B0 -> J/psi K*0 pi+ pi-) = (8.0 +- 2.2 +- 1.5) * 10^{-4} and BR(B0 -> J/psi K0 pi+ pi-) = (1.1 +- 0.4 +- 0.2) * 10^{-3}. Contributions to these decays are seen from psi(2S) K(*)0, J/psi K0 rho0, J/psi K*+ pi-, and J/psi K1(1270).

hep-ex↗

arXiv2001

Search for Gluinos and Squarks Using Like-Sign Dileptons in p-pbar Collisions at sqrt(s)=1.8 TeV

We present results of the first search for like-sign dilepton (ee, eμ, μμ) events associated with multijets and large missing energy using 106 pb^-1 of data in p-pbar collisions at sqrt(s)=1.8 TeV collected during 1992-95 by the CDF experiment. Finding no events that pass our selection, we examine pair-production of gluinos and squarks in a constrained framework of the Minimal Supersymmetric Standard Model. At tan_beta = 2 and μ=-800 GeV/c^2, we set 95% confidence level limits of M(gluino) > 221 GeV/c^2 for M(gluino) \simeq M(squark), and M(gluino) > 168 GeV/c^2 for M(squark) \gg M(gluino), both with small variation as a function of μ.

hep-ex↗

arXiv2001

Measurement of the $t\bar{t} production cross section in $p\bar{p}$ collisions at $\sqrt{s}$ = 1.8 TeV

We update the measurement of the top production cross section using the CDF detector at the Fermilab Tevatron. This measurement uses $t\bar{t}$ decays to the final states $e+ν$+jets and $μ+ν$+jets. We search for $b$ quarks from $t$ decays via secondary-vertex identification or the identification of semileptonic decays of the $b$ and cascade $c$ quarks. The background to the $t\bar{t}$ production is determined primarily through a Monte Carlo simulation. However, we calibrate the simulation and evaluate its uncertainty using several independent data samples. For a top mass of 175 $GeV/c^2$, we measure $σ_{t\bar{t}}=5.1 \pm 1.5$ pb and $σ_{t\bar{t}}=9.2 \pm 4.3$ pb using the secondary vertex and the lepton tagging algorithms, respectively. Finally, we combine these results with those from other $t\bar{t}$ decay channels and obtain $σ_{t\bar{t}} = 6.5^{+1.7}_{-1.4}$ pb.

hep-ex↗

arXiv2000

First Measurement of the Ratio B(t-->Wb)/B(t-->Wq) and Associated Limit on the CKM Element Vtb

We present the first measurement of the ratio of branching fraction R= B(t-->wb)/B(t-->Wq) from ppbar collisions at sqrt(s)=1.8 TeV. The data set corresponds to 109 pb-1 of data recorded by the Collider Detector at Fermilab during the 1992-1995 Tevatron run. We measure R=0.94+.31-.24 (stat+syst) or R>0.61 (0.56) at 90 (95) %C.L., in agreement with the standard model predictions. This measurement yields a limit of the Cabibbo-Kobayashi-Maskawa quark mixing matrix element Vtb under the assumption of three generation unitarity.

hep-ex↗

arXiv2000

Measurement of the Two-Jet Differential Cross Section in proton-antiproton Collisions at sqrt{s} = 1800 GeV

A measurement is presented of the two-jet differential cross section, d^3σ/dE_T dη_1 dη_2, at center of mass energy sqrt{s} = 1800 GeV in proton-antiproton collisions. The results are based on an integrated luminosity of 86 pb^-1 collected during 1994-1995 by the CDF collaboration at the Fermilab Tevatron collider. The differential cross section is measured as a function of the transverse energy, E_T, of a jet in the pseudorapidity region 0.1 < |eta_1| < 0.7 for four different pseudorapidity bins of a second jet restricted to 0.1 < |η_2| < 3.0. The results are compared with next-to-leading order QCD calculations determined using the CTEQ4 and MRST sets of parton distribution functions. None of the sets examined in this analysis provides a good description of the data.

hep-ex↗

arXiv2000

Search for the Supersymmetric Partner of the Top-Quark in $p \bar{p}$ Collisions at $\sqrt{s} = 1.8 {\rm TeV}$

We report on a search for the supersymmetric partner of the top quark (stop) produced in $t \bar{t}$ events using $110 {\rm pb}^{-1}$ of $p \bar{p}$ collisions at $\sqrt{s} = 1.8 {\rm TeV}$ recorded with the Collider Detector at Fermilab. In the case of a light stop squark, the decay of the top quark into stop plus the lightest supersymmetric particle (LSP) could have a significant branching ratio. The observed events are consistent with Standard Model $t \bar{t}$ production and decay. Hence, we set limits on the branching ratio of the top quark decaying into stop plus LSP, excluding branching ratios above 45% for a LSP mass up to 40 {\rm GeV/c}$^{2}$.

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