Search

The first measurement of the true top quark PT distributon was carried out. An attempt was also made to compute a 95% confidence level upper limit on the fraction of top quarks that are produced with 225 > PT > 425 GeV/c. It was found that R4 > 0.16 at 95% C.L.

We report two measurements of the top-quark mass M(top) using the CDF II detector at the Fermilab Tevatron in a 318 pb(-1) data sample of tt events in the lepton+jets final state. One method uses an event-based likelihood technique resulting in M(top) = 173.2(-2.4)(+2.6)(stat) +/- 3.2(syst) GeV/c2 or 173.2(-4.0)(+4.1) GeV/c2. The second method reconstructs a top-quark mass in each event using the measured invariant mass of the hadronically decaying W boson to constrain the jet energy scale to obtain a value for M(top)of 173.5(-3.6)(+3.7)(stat) +/- 1.3(syst) GeV/c2 or 173.5(-3.8)(+3.9) GeV/c2 . We take the latter, which is more precise, as our result.

We report on measurements of differential cross sections dsigma/dp(T) for prompt charm meson production in ppmacr; collisions at sqrt[s]=1.96 TeV using 5.8+/-0.3 pb(-1) of data from the CDF II detector at the Fermilab Tevatron. The data are collected with a new trigger that is sensitive to the long lifetime of hadrons containing heavy flavor. The charm meson cross sections are measured in the central rapidity region |y|K-pi(+), D(*+)-->D0pi(+), D+-->K-pi(+)pi(+), D(+)(s)-->phipi(+), and their charge conjugates. The measured cross sections are compared to theoretical calculations.

The decay mechanisms of Bs0 → μ +μ- and Bd0 → μ +μ- in pp̄ collisions were investigated. For discrimination of the decays from background events, four variables were used such as invariant mass of muon pair, B-candidate proper decay length, opening angle between B-hadron flight direction and B-candidate track isolation. A 'blind' analysis technique was also used for determination of optimal selection criteria for four variables. The results show that optimal set of selection criteria uses ∓80 MeV/c2 search window around B s0 mass, and I > 0.65.

We report a measurement of the tt production cross section using dilepton events with jets and missing transverse energy in pp 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 tt production cross section of 7.0(+2.4)(-2.1)(stat)+1.6-1.1(syst)+/-0.4(lum) pb.

We report on a search for narrow-width particles decaying to a top and antitop quark pair. The data set used in the analysis corresponds to an integrated luminosity of 680pb-1 collected with the Collider Detector at Fermilab in run II. We present 95% confidence level upper limits on the cross section times branching ratio. Assuming a specific top-color-assisted technicolor production model, the leptophobic Z′ with width ΓZ′=0.012MZ′, we exclude the mass range MZ′

We have studied the production of B hadrons in 1.8-TeV pp[over ¯] collisions. We present measurements of the fragmentation fractions, f_{u}, f_{d}, f_{s}, and f_{baryon}, of produced b quarks that yield B^{+}, B^{0}, B_{s}^{0}, and Λ[over ¯]_{b}^{0} hadrons. Reconstruction of five electron-charm final states yields f_{s}/( f_{u}+f_{d})=0.213±0.068 and f_{baryon}/( f_{u}+f_{d})=0.118±0.042, assuming f_{u}=f_{d}. If all B hadrons produced in pp[over ¯] collisions cascade to one of these four hadrons, we determine f_{u}=f_{d}=0.375±0.023, f_{s}=0.160±0.044, and f_{baryon}=0.090±0.029. If we do not assume f_{u}=f_{d}, we find f_{d}/f_{u}=0.84±0.16.

Results on a search for pair production of second-generation scalar leptoquark in pp̄ collisions at s=1.96TeV are reported. The data analyzed were collected by the CDF detector during the 2002-2003 Tevatron Run II and correspond to an integrated luminosity of 198pb-1. Leptoquarks (LQ) are sought through their decay into (charged) leptons and quarks, with final state signatures represented by two muons and jets and one muon, large transverse missing energy and jets. We observe no evidence for LQ production and derive 95% C.L. upper limits on the LQ production cross sections as well as lower limits on their mass as a function of β, where β is the branching fraction for LQ→μq. © 2006 The American Physical Society.

We have performed a search for B(s)(0) --> micro(+) micro(-) and B(0) --> micro(+) micro(-) decays in pp collisions at square root s = 1.96 TeV using 2 fb(-1) of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron Collider. The observed number of B(s)(0) and B0 candidates is consistent with background expectations. The resulting upper limits on the branching fractions are B(B(s)0) --> micro(+) micro(-)) micro(+) micro(-))

We report a measurement of the diffractive structure function F(D)(jj) of the antiproton obtained from a study of dijet events produced in association with a leading antiproton in pp collisions at sqrt[s] = 630 GeV at the Fermilab Tevatron. The ratio of F(D)(jj) at sqrt[s] = 630 GeV to F(D)(jj) obtained from a similar measurement at sqrt[s] = 1800 GeV is compared with expectations from QCD factorization and other theoretical predictions. We also report a measurement of the xi ( x-Pomeron) and beta ( x of parton in Pomeron) dependence of F(D)(jj) at sqrt[s] = 1800 GeV. In the region 0.035

Inclusive jet cross sections in Z/γ* events, with Z/γ* decaying into an electron-positron pair, are measured as a function of jet transverse momentum and jet multiplicity in pp̄ collisions at s=1.96 TeV with the upgraded Collider Detector at Fermilab in run II, based on an integrated luminosity of 1.7 fb-1. The measurements cover the rapidity region |yjet|30GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections. © 2008 The American Physical Society.

We present searches for quark-lepton compositeness and a heavy W' boson at high electron-neutrino transverse mass. We use approximately 110 pb(-1) of data collected in p p macro collisions at square root of [s] = 1.8 TeV by the CDF Collaboration during 1992-1995. The data are consistent with standard model expectations. Limits are set on the quark-lepton compositeness scale Lambda, the ratio of partial cross sections sigma(W'-->enu)/sigma(W-->enu), and the mass of a W' boson with standard model couplings. We exclude Lambda

We present the first measurement of the jet pseudorapidity distribution in direct photon events from a sample of pp̄ collisions at √s= 1.8 TeV, recorded with the Collider Detector at Fermilab. Quantum chromodynamics (QCD) predicts that these events are primarily from hard quark-gluon Compton scattering, qg→qγ, with the final state quark producing the jet of hadrons. The jet pseudorapidity distribution in this model is sensitive to parton momentum fractions between 0.015 and 0.15. We find that the shape of the measured pseudorapidity distribution agrees well with next-to-leading order QCD calculations.

We present a measurement of the tt̄ production cross section using events with one charged lepton and jets from pp̄ 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 tt̄ production cross section of 5.6-1.1+1.2(stat.)-0.6+0.9(syst.) pb. © 2005 The American Physical Society.

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 √s = 1800 GeV and √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 pseudorapidity, η, as the jet with the highest transverse energy (ET(1)), and at ±90° 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 ET(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 was carried out using data from the CDF detector taken during Run 1 (1994-1995). The study will help improve the precision of comparisons of jet cross section data and NLO perturbative QCD predictions. The distribution of the sum of the track momenta in the two cones is also examined for five different ET(1) bins. The HERWIG and PYTHIA Monte Carlo generators are reasonably successful in describing the data, but neither can describe completely all of the event properties.

We search for evidence of resonant top quark pair production in 955 pb-1 of pp̄ collisions at s=1.96TeV recorded with the CDF II detector at the Fermilab Tevatron. For fully reconstructed candidate tt̄ events triggered on leptons with large transverse momentum and containing at least one identified b-quark jet, we compare the invariant mass spectrum of tt̄ pairs to the expected superposition of standard model tt̄, non-tt̄ backgrounds, and a simple resonance model based on a sequential Z′ boson. We establish upper limits for σ(pp̄→Z′) ·Br(Z′→tt̄) in the Z′ mass interval from 450GeV/c2 to 900GeV/c2. A topcolor leptophobic Z′ is ruled out below 720GeV/c2, and the cross section of any narrow Z′-like state decaying to tt̄ is found to be less than 0.64 pb at 95% C.L. for MZ′ above 700GeV/c2. © 2008 The American Physical Society.

We measure the ratio of cross section times branching fraction, Rp=sigma chi c2 B(chi c2-->J/psi gamma)/sigma chi c1 B(chi c1-->J/psi gamma), in 1.1 fb(-1) of pp collisions at square root s=1.96 TeV. This measurement covers the kinematic range pT(J/psi)>4.0 GeV/c, |eta(J/psi)1.0 GeV/c. For events due to prompt processes, we find Rp=0.395+/-0.016(stat)+/-0.015(syst). This result represents a significant improvement in precision over previous measurements of prompt chi c1,2 hadro production.

We present a measurement of the mass of the top quark from proton-antiproton collisions recorded at the CDF experiment in Run II of the Fermilab Tevatron. We analyze events from the single lepton plus jets final state (tt-->W(+)bW(-)b-->lnubqq'b). The top-quark mass is extracted using a direct calculation of the probability density that each event corresponds to the tt final state. The probability is a function of both the mass of the top quark and the energy scale of the calorimeter jets, which is constrained in situ by the hadronic W boson mass. Using 167 events observed in 955 pb(-1) of integrated luminosity, we achieve the single most precise measurement of the top-quark mass, 170.8+/-2.2(stat.)+/-1.4(syst.) GeV/c(2).

We report an observation of new bottom baryons produced in pp̄ collisions at the Tevatron. Using 1.1fb-1 of data collected by the CDF II detector, we observe four Λb0π± resonances in the fully reconstructed decay mode Λb0→Λc+π-, where Λc+→pK-π+. We interpret these states as the Σb(*) ± baryons and measure the following masses: mΣb+=5807.8-2.2+2. 0(stat.)±1.7(syst.)MeV/c2, mΣb-=5815.2±1.0(stat.)±1. 7(syst.)MeV/c2, and m(Σb*)-m(Σb)=21.2-1.9+2.0(stat.)-0.3+0. 4(syst.)MeV/c2. © 2007 The American Physical Society.

We report a measurement of the rate of prompt diphoton production in pp collisions at square root of s=1.96 TeV using a data sample of 207 pb(-1) collected with the upgraded Collider Detector at Fermilab. The background from nonprompt sources is determined using a statistical method based on differences in the electromagnetic showers. The cross section is measured as a function of the diphoton mass, the transverse momentum of the diphoton system, and the azimuthal angle between the two photons and is found to be consistent with perturbative QCD predictions.

The ratio of the branching fraction from particle collisions were measured. The data was recorded by the Collider Detector at fermilab during the Tevatron run. The measured values were in agreement with the standard model predictions. The measurements yielded a limit on the Cabibbo-Kobayashi-Maskawa quark mixing matrix element.

We present the first measurement of the production cross section of a W boson with a single charm quark (c) in pp collisions at sqrt(s)=1.96 TeV, using soft muon tagging of c jets. In a data sample of approximately 1.8 fb(-1), recorded with the Collider Detector at Fermilab II detector at the Fermilab Tevatron, we select events with W+1 or 2 jets. We use the charge correlation between the W and the muon from the semileptonic decay of a charm hadron to extract the Wc signal. We measure sigma Wc(PTc >20 GeV/c,|eta c|l nu)=9.8+/-3.2 pb, in agreement with theoretical expectations.

Neutron Higgs bosons produced in association with `b' quarks were investigated. Experimental results showed that there was no evidence for the existence of such a signal. The data was interpreted using the Neutral Higgs sector of the supersymmetric extension of standard model. The lower mass limits for neutral Higgs bosons were derived for tanβ values in excess of 35.

We search for decays of the type B(s)0-->h+ h'- (where h,h' = K or pi) in 180 pb(-1) of pp collisions collected at the Tevatron by the upgraded Collider Detector at Fermilab. We report the first observation of the new mode B(s)0-->K+ K- with a yield of 236+/-32 events, corresponding to (fs/fd) x B(B(s)0-->K+ K-)/B(B0-->K+ pi-) = 0.46+/-0.08stat+/-0.07syst, where fs/fd is the ratio of production fractions of B(s)0 and B0. We find results in agreement with world averages for the B0 modes, and set the following new limits at 90% C.L.: B(B(s)0-->K- pi+) < 5.6 x 10(-6) and B(B(s)0-->pi+ pi-) < 1.7 x 10(-6).

We use the three lepton and missing energy trilepton signature to search for chargino-neutralino production with 2.0 fb;{-1} of integrated luminosity collected by the CDF II experiment at the Tevatron pp[over ] collider. We expect an excess of approximately 11 supersymmetric events for a choice of parameters of the mSUGRA model, but our observation of 7 events is consistent with the standard model expectation of 6.4 events. We constrain the mSUGRA model of supersymmetry and rule out chargino masses up to 145 GeV/c;{2} for a specific choice of parameters.

We report on measurements of the inclusive jet production cross section as a function of the jet transverse momentum in pp̄ collisions at s=1.96TeV, using the kT algorithm and a data sample corresponding to 1.0fb-1 collected with the Collider Detector at Fermilab in run II. The measurements are carried out in five different jet rapidity regions with |yjet

Events collected by the Collider Detector at Fermilab (CDF) with an energetic jet plus large missing transverse energy can be used to search for physics beyond the standard model. We see no deviations from the expected backgrounds and set upper limits on the production of new processes. We consider in addition the production of light gravitinos and set a limit at 95% confidence level on the breaking scale √F ≥ 217 GeV, which excludes gravitino masses smaller than 1.1 × 10-5 eV/c2. © 2000 The American Physical Society.

Doubly charged Higgs bosons decaying to dileptons in pp̈ collisions at √s=1.96 TeV were searched. An inclusive search for double charged resonances in same-sign ee data with m ee> 100 GeV / c 2, and same sign μμ and eμ data with m ll'> 80 GeV / c 2, was performed. The acceptance systematic uncertainty was dominated by the parton distribution function uncertainty, which was estimated to be 4% using the Martin-Roberts-Stirling-Thorne prescription. No new evidence for doubly charged resonances was found, and the extended mass limit was extended on doubly charged decaying Higgs bosons.

A search for anomalous production of events with at least two charged, isolated, like-sign leptons was discussed. A signal region, which contains low background from standard model (SM) processes, was defined. The final cuts, before examining the event yield in the signal region, were fixed, to avoid bias. A 95% confidence level limits on new physics processes in both a signature-based context as well as within a representative minimal supergravity model were presented.

We report on measurements of the branching ratios of the decays B +→χc10(1P)K+ and B + → J/ψK+ π+π-, where χc10(1P) → J/ψγ and J/ψ → μ+μ- in pp→ collisions at √s = 1.8 TeV. Using a data sample from an integrated luminosity of 110 pb-1 collected by the Collider Detector at Fermilab we measure the branching ratios to be BR(B+ → χc10(1P)K+) = 15.5±5.4(stat) ± 1.5(syst)± 1.3(br) × 10 -4 and BR(B+ →J/ψK+ π+ π-) = 6.9±1.8(stat)±1.1(syst)±0.4(br) × 10-4 where (br) is due to the finite precision on BR(B+ → J/ψK+), BR(χc10(1P) → J/ψγ) is used to normalize the signal yield, and (syst) encompasses all other systematic uncertainties. © 2002 The American Physical Society.

We present the first measurement of the A2 and A3 angular coefficients of the W boson produced in proton-antiproton collisions. We study W→eνe and W→μνμ candidate events produced in association with at least one jet at CDF, during Run Ia and Run Ib of the Tevatron at s=1.8TeV. The corresponding integrated luminosity was 110pb-1. The jet balances the transverse momentum of the W and introduces QCD effects in W boson production. The extraction of the angular coefficients is achieved through the direct measurement of the azimuthal angle of the charged lepton in the Collins-Soper rest-frame of the W boson. The angular coefficients are measured as a function of the transverse momentum of the W boson. The electron, muon, and combined results are in good agreement with the standard model prediction, up to order αs2 in QCD. © 2006 The American Physical Society.

We report on a study of jet shapes in inclusive jet production in pp̄ collisions at s=1.96 TeV using the upgraded collider detector at Fermilab in Run II (CDF II) and based on an integrated luminosity of 170 pb-1. Measurements are carried out on jets with rapidity 0.1