Combined Tevatron upper limit on gg->H->W+W- and constraints on the Higgs boson mass in fourth-generation fermion models

We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg->H->W+W- in p=pbar collisions at the Fermilab Tevatron Collider at sqrt{s}=1.96 TeV. With 4.8 fb-1 of integrated luminosity analyzed at CDF and 5.4 fb-1 at D0, the 95% Confidence Level upper limit on \sigma(gg->H) x B(H->W+W-) is 1.75 pb at m_H=120 GeV, 0.38 pb at m_H=165 GeV, and 0.83 pb at m_H=200 GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% Confidence Level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.

First Measurement of the b-Jet Cross Section in Events with a W Boson in pp̅ Collisions at √s=1.96 TeV

The cross section for jets from b quarks produced with a W boson has been measured in ppbar collision data from 1.9/fb of integrated luminosity recorded by the CDF II detector at the Tevatron. The W+b-jets process poses a significant background in measurements of top quark production and prominent searches for the Higgs boson. We measure a b-jet cross section of 2.74 +- 0.27(stat.) +- 0.42(syst.) pb in association with a single flavor of leptonic W boson decay over a limited kinematic phase space. This measured result cannot be accommodated in several available theoretical predictions.

Measurement of W-Boson Polarization in Top-Quark Decay in pp̅ Collisions at √s=1.96 TeV

We report measurements of the polarization of W bosons from top-quark decays using 2.7 fb^-1 of ppbar collisions collected by the CDF II detector. Assuming a top-quark mass of 175 GeV/c^2, three measurements are performed. A simultaneous measurement of the fraction of longitudinal (f_0) and right-handed (f_+) W bosons yields the model-independent results f_0 = 0.88 \pm 0.11 (stat) \pm 0.06 (syst) and f_+ = -0.15 \pm 0.07 (stat) \pm 0.06 (syst) with a correlation coefficient of -0.59. A measurement of f_0 (f_+) constraining f_+ (f_0) to its standard model value of 0.0 (0.7) yields f_0 = 0.70 \pm 0.07 (stat) \pm 0.04 (syst) (f_+ = -0.01 \pm 0.02 (stat) \pm 0.05 (syst)). All these results are consistent with standard model expectations.

Search for Technicolor Particles Produced in Association with a W Boson at CDF

We present a search for the technicolor particles $\rho_{T}$ and $\pi_{T}$ in the process $p\bar{p} \to \rho_{T} \to W\pi_{T}$ at a center of mass energy of $\sqrt{s}=1.96 \mathrm{TeV}$. The search uses a data sample corresponding to approximately $1.9 \mathrm{fb}^{-1}$ of integrated luminosity accumulated by the CDF II detector at the Fermilab Tevatron. The event signature we consider is $W\to \ell\nu$ and $\pi_{T} \to b\bar{b}, b\bar{c}$ or $b\bar{u}$ depending on the $\pi_{T}$ charge. We select events with a single high-$p_T$ electron or muon, large missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with multiple $b$-tagging algorithms. The observed number of events and the invariant mass distributions are consistent with the standard model background expectations, and we exclude a region at 95% confidence level in the $\rho_T$-$\pi_T$ mass plane. As a result, a large fraction of the region $m(\rho_T) = 180$ - $250 \mathrm{GeV}/c^2$ and $m(\pi_T) = 95$ - $145 \mathrm{GeV}/c^2$ is excluded.

Search for New Bottomlike Quark Pair Decays QQ̅ →(tW∓)(t̅ W±) in Same-Charge Dilepton Events

We report the most restrictive direct limits on masses of fourth-generation down-type quarks b′, and quarklike composite fermions (B or T5/3), decaying promptly to tW∓. We search for a significant excess of events with two same-charge leptons (e, μ), several hadronic jets, and missing transverse energy. An analysis of data from pp̅ collisions with an integrated luminosity of 2.7  fb-1 collected with the CDF II detector at Fermilab yields no evidence for such a signal, setting mass limits mb′, mB>338  GeV/c2 and mT5/3>365  GeV/c2 at 95% confidence level.

Search for New Bottomlike Quark Pair Decays QQ̅ →(tW∓)(t̅ W±) in Same-Charge Dilepton Events

We report the most restrictive direct limits on masses of fourth-generation down-type quarks $b^{\prime}$, and quark-like composite fermions ($B$ or $T_{5/3}$), decaying promptly to $t W^{\mp}$. We search for a significant excess of events with two same-charge leptons ($e$, $\mu$), several hadronic jets, and missing transverse energy. An analysis of data from $p\overline{p}$ collisions with an integrated luminosity of 2.7 fb$^{-1}$ collected with the CDF II detector at Fermilab yields no evidence for such a signal, setting mass limits $m_{b^{\prime}}, m_{B} >$ 338 $\mathrm{GeV}/c^2$ and $m_{T_{5/3}} >$ 365 $\mathrm{GeV}/c^2$ at 95% confidence level.

Diffractive W and Z production at the Fermilab Tevatron

We report on a measurement of the fraction of events with a W or Z boson produced diffractively in antiproton-proton collisions at a center of mass energy of 1.96 TeV, using data from 0.6 inverse femtobarns of integrated luminosity collected with the CDF-II detector equipped with a Roman-pot spectrometer that detects the antiproton (pbar) from pbar+p --> pbar+[X+W/Z]. We find that (0.97 +/- 0.11)% of Ws and (0.85 +/- 0.22)% of Zs are produced diffractively in a region of (anti)proton fractional momentum loss (\xi) of 0.03-1t p+[X+W/Z]+pbar, and on exclusive Z production, pbar+p-->pbar+Z+p. No signal is seen above background for these processes, and comparisons are made with expectations.

Direct Measurement of the W Production Charge Asymmetry in pp̅ Collisions at √s=1.96 TeV

We present the first direct measurement of the $W$ production charge asymmetry as a function of the $W$ boson rapidity $\yW$ in $\ppbar$ collisions at $\sqrt{s} = 1.96$ $\TeV$. We use a sample of $\wenu$ events in data from 1 $\ifb$ of integrated luminosity collected using the CDF II detector. In the region $|\yW|

Search for Top-Quark Production via Flavor-Changing Neutral Currents in W+1 Jet Events at CDF

We report on the first search for top-quark production via flavor-changing neutral-current (FCNC) interactions in the non-standard-model process u(c)+g -> t using ppbar collision data collected by the CDF II detector. The data set corresponds to an integrated luminosity of 2.2/fb. The candidate events feature the signature of semileptonic top-quark decays and are classified as signal-like or background-like by an artificial neural network trained on simulated events. The observed discriminant distribution is in good agreement with the one predicted by the standard model and provides no evidence for FCNC top-quark production, resulting in a Bayesian upper limit on the production cross section sigma (u(c)+g -> t) u+g) c+g)

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.

Crystallographic Evolution, Dielectric, and Piezoelectric Properties of Bi4Ti3O12:W/Cr Ceramics

W/Cr codoped Bi4Ti3O12 ceramics, Bi4Ti3-xWxO12+x+0.2 wt%Cr2O3 (BITWC, x=0-0.15), were prepared using a solid-state reaction method. The crystallographic evolution and phase analysis were distinctly determined focusing on the X-ray diffraction peak changes in (020)/(200) and (220)/(1115) diffraction planes, by which the lattice parameters, a, b, and c can be refined. The thermal variations of permittivity, dielectric loss (tan delta), impedance, and electrical conductivity properties were characterized. A decrease in the values of Curie temperature from 675 degrees to 640 degrees C and an increase in the values of the dielectric constant due to an increase of W6+/Cr3+ content were observed. The highest piezoelectric constant, d(33) of 22 pC/N, was achieved with the composition of Bi4Ti2.975W0.025O12.025+0.2 wt% Cr2O3. Also, this composition had a lower electrical conductivity than the other investigated compositions.

Silva Fennica Vol. 3. 1969.

Julkaistu Silva Fennica Vol. 4(1) -numeron liitteenä.