Search for Anomalous Production of Events with a Photon, Jet, b-quark Jet, and Missing Transverse Energy

We present a signature-based search for anomalous production of events containing a photon, two jets, of which at least one is identified as originating from a b quark, and missing transverse energy. The search uses data corresponding to 2.0/fb of integrated luminosity from p-pbar collisions at a center-of-mass energy of sqrt(s)=1.96 TeV, collected with the CDF II detector at the Fermilab Tevatron. From 6,697,466 events with a photon candidate with transverse energy ET> 25 GeV, we find 617 events with missing transverse energy > 25 GeV and two or more jets with ET> 15 GeV, at least one identified as originating from a b quark, versus an expectation of 607+- 113 events. Increasing the requirement on missing transverse energy to 50 GeV, we find 28 events versus an expectation of 30+-11 events. We find no indications of non-standard-model phenomena.

Search for standard model Higgs boson production in association with a W boson using a neural network discriminant at CDF

We present a search for standard model Higgs boson production in association with a W boson in proton-antiproton collisions at a center of mass energy of 1.96 TeV. The search employs data collected with the CDF II detector that correspond to an integrated luminosity of approximately 1.9 inverse fb. We select events consistent with a signature of a single charged lepton, missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with a secondary vertex tagging method, a jet probability tagging method, and a neural network filter. We use kinematic information in an artificial neural network to improve discrimination between signal and background compared to previous analyses. The observed number of events and the neural network output distributions are consistent with the standard model background expectations, and we set 95% confidence level upper limits on the production cross section times branching fraction ranging from 1.2 to 1.1 pb or 7.5 to 102 times the standard model expectation for Higgs boson masses from 110 to $150 GeV/c^2, respectively.

Search for narrow resonances lighter than ϒ mesons

We report a search for narrow resonances, produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV, that decay into muon pairs with invariant mass between 6.3 and 9.0 GeV/c^2. The data, collected with the CDF~II detector at the Fermilab Tevatron collider, correspond to an integrated luminosity of 630 pb$^{-1}$. We use the dimuon invariant mass distribution to set 90% upper credible limits of about 1% to the ratio of the production cross section times muonic branching fraction of possible narrow resonances to that of the $\Upsilon(1{\rm S})$ meson.

Search for the Production of Narrow tb̅ Resonances in 1.9 fb-1 of pp̅ Collisions at √s=1.96 TeV

We present new limits on resonant tb production in proton-antiproton collisions at 1.96 TeV, using 1.9 fb^-1 of data recorded with the CDF II detector at the Fermilab Tevatron. We reconstruct a candidate mass in events with a lepton, neutrino candidate, and two or three jets, and search for anomalous tb production as modeled by W'->tb. We set a new limit on a right-handed W' with standard model-like coupling, excluding any mass below 800 GeV at 95% C.L. The cross-section for any narrow, resonant tb production between 750 and 950 GeV is found to be less than 0.28 pb at 95% C.L. We also present an exclusion of the W' coupling strength versus W' mass over the range 300 to 950 GeV.

Updated search for the flavor-changing neutral-current decay D0→μ+μ- in pp̅ collisions at √s=1.96 TeV

We report on a search for the flavor-changing neutral-current decay D0 \to {\mu}+ {\mu}- in pp collisions at \surd s = 1.96 TeV using 360 pb-1 of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron collider. A displaced vertex trigger selects long-lived D0 candidates in the {\mu}+ {\mu}-, {\pi}+{\pi}-, and K-{\pi}+ decay modes. We use the Cabibbo-favored D0 \to K-{\pi}+ channel to optimize the selection criteria in an unbiased manner, and the kinematically similar D0 \to{\pi}+ {\pi}- channel for normalization. We set an upper limit on the branching fraction (D0 --> {\mu}+ {\mu}-)

Improved Search for a Higgs Boson Produced in Association with Z→l+l- in pp̅ Collisions at √s=1.96 TeV

We present a search for the standard model Higgs boson produced with a Z boson in 4.1 fb^-1 of data collected with the CDF II detector at the Tevatron. In events consistent with the decay of the Higgs boson to a bottom-quark pair and the Z boson to electrons or muons, we set 95% credibility level upper limits on the ZH production cross section times the H -> b bbar branching ratio. Improved analysis methods enhance signal sensitivity by 20% relative to previous searches beyond the gain due to the larger data sample. At a Higgs boson mass of 115 GeV/c^2 we set a limit of 5.9 times the standard model value.

Search for Anomalous Production of Events with Two Photons and Additional Energetic Objects at CDF

We present results of a search for anomalous production of two photons together with an electron, muon, $\tau$ lepton, missing transverse energy, or jets using $p\bar{p}$ collision data from 1.1-2.0 fb$^{-1}$ of integrated luminosity collected by the Collider Detector at Fermilab (CDF). The event yields and kinematic distributions are examined for signs of new physics without favoring a specific model of new physics. The results are consistent with the standard model expectations. The search employs several new analysis techniques that significantly reduce instrumental backgrounds in channels with an electron and missing transverse energy.

Search for New Physics with a Dijet Plus Missing ET Signature in pp̅ Collisions at √s=1.96 TeV

We present results of a signature-based search for new physics using a dijet plus missing transverse energy data sample collected in 2 fb-1 of p-pbar collisions at sqrt(s) = 1.96 TeV with the CDF II detector at the Fermilab Tevatron. We observe no significant event excess with respect to the standard model prediction and extract a 95% C.L. upper limit on the cross section times acceptance for a potential contribution from a non-standard model process. Based on this limit the mass of a first or second generation scalar leptoquark is constrained to be above 187 GeV/c^2.

Search for Bs0→μ+μ- and B0→μ+μ- Decays with 2 fb-1 of pp̅ Collisions

We have performed a search for Bs0→μ+μ- and B0→μ+μ- decays in pp̅ collisions at √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 Bs0 and B0 candidates is consistent with background expectations. The resulting upper limits on the branching fractions are B(Bs0→μ+μ-)<5.8×10-8 and B(B0→μ+μ-)<1.8×10-8 at 95% C.L.

Search for Exclusive Z-Boson Production and Observation of High-Mass pp̅ →pγγp̅ →pl+l-p̅ Events in pp̅ Collisions at √s=1.96 TeV

We present a search for exclusive Z boson production in proton-antiproton collisions at sqrt(s) = 1.96 TeV, using the CDF II detector at Fermilab. We observe no exclusive Z->ll candidates and place the first upper limit on the exclusive Z cross section in hadron collisions, sigma(exclu) gammagamma->p+ll+pbar, and measure the cross section for M(ll) > 40 GeV/c2 and |eta(l)|

Search for new particles decaying into dijets in proton-antiproton collisions at √s=1.96 TeV

We present a search for new particles whose decays produce two jets (dijets) using proton-antiproton collision data corresponding to an integrated luminosity of 1.13 fb-1 collected with the CDF II detector. The measured dijet mass spectrum is found to be consistent with next-to-leading-order perturbative QCD predictions, and no significant evidence of new particles is found. We set upper limits at the 95% confidence level on cross sections times the branching fraction for the production of new particles decaying into dijets with both jets having a rapidity magnitude |y|

Search for Bs0→μ+μ- and B0→μ+μ- Decays with 2 fb-1 of pp̅ Collisions

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

Search for new color-octet vector particle decaying to t tbar in p pbar collisions at sqrt{s} = 1.96 TeV

We present the result of a search for a massive color-octet vector particle, (e.g. a massive gluon) decaying to a pair of top quarks in proton-antiproton collisions with a center-of-mass energy of 1.96 TeV. This search is based on 1.9 fb$^{-1}$ of data collected using the CDF detector during Run II of the Tevatron at Fermilab. We study $t\bar{t}$ events in the lepton+jets channel with at least one $b$-tagged jet. A massive gluon is characterized by its mass, decay width, and the strength of its coupling to quarks. These parameters are determined according to the observed invariant mass distribution of top quark pairs. We set limits on the massive gluon coupling strength for masses between 400 and 800 GeV$/c^2$ and width-to-mass ratios between 0.05 and 0.50. The coupling strength of the hypothetical massive gluon to quarks is consistent with zero within the explored parameter space.

Search for the Decays B(s)0→e+μ- and B(s)0→e+e- in CDF Run II

We report results from a search for the lepton flavor violating decays $B^0_{(s)}\to e^+\mu^-$, and the flavor-changing neutral-current decays $B^0_{(s)} \to e^+ e^-$. The analysis uses data corresponding to ${\rm 2 fb^{-1}}$ of integrated luminosity of $p \bar{p}$ collisions at $\sqrt{s}=1.96 {\rm TeV}$ collected with the upgraded Collider Detector (CDF II) at the Fermilab Tevatron. The observed number of $B^0_{(s)}$ candidates is consistent with background expectations. The resulting Bayesian upper limits on the branching ratios at 90% credibility level are $\mathcal{B}(B^0_s \to e^{+}\mu^{-}) e^{+}\mu^{-})e^{+}\mu^{-}) 47.8 {\rm TeV/c^2}$, and ${M_{LQ}}(B^0\to e^+ \mu^-) > 59.3 {\rm TeV/c^2}$, at 90% credibility level.

Interfacial microrheology as a tool to study viscoelastic transitions in nanoconfined soft matter

We present a method to perform in situ microrheological measurements on monolayers of soft materials undergoing viscoelastic transitions under compression. Using the combination of a Langmuir trough mounted on the inverted microscope stage of a laser scanning confocal microscope we track the motion of individual fluorescent quantum dots partly dispersed in monolayers spread at the air-water interface. From the calculated mean square displacement of the probe particles and extending a well established scheme of the generalized Stokes-Einstein relation in bulk to the interface we arrive at the viscoelastic modulus for the respective monolayers as a function of surface density. Measurements on monolayers of glassy as well as nonglassy polymers and a standard fatty acid clearly show sensitivity of our technique to subtle variations, in the viscoelastic properties of the highly confined materials under compression. Evidence for possible spatial variations of such viscoelastic properties at a given surface density for the fatty acid monolayer is also provided.