270 research outputs found

    Flux flow of Abrikosov-Josephson vortices along grain boundaries in high-temperature superconductors

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    We show that low-angle grain boundaries (GB) in high-temperature superconductors exhibit intermediate Abrikosov vortices with Josephson cores, whose length ll along GB is smaller that the London penetration depth, but larger than the coherence length. We found an exact solution for a periodic vortex structure moving along GB in a magnetic field HH and calculated the flux flow resistivity RF(H)R_F(H), and the nonlinear voltage-current characteristics. The predicted RF(H)R_F(H) dependence describes well our experimental data on 7∘7^{\circ} unirradiated and irradiated YBa2Cu3O7YBa_2Cu_3O_7 bicrystals, from which the core size l(T)l(T), and the intrinsic depairing density Jb(T)J_b(T) on nanoscales of few GB dislocations were measured for the first time. The observed temperature dependence of Jb(T)=Jb0(1−T/Tc)2J_b(T)=J_{b0}(1-T/T_c)^2 indicates a significant order parameter suppression in current channels between GB dislocation cores.Comment: 5 pages 5 figures. Phys. Rev. Lett. (accepted

    Inflammatory myofibroblastic tumor after lung transplant-A rare and aggressive complication. A case report.

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    Introduction Malignant diseases are well-known complications after lung transplantation (LT). Among these, inflammatory myofibroblastic tumor (IMT) is a rare neoplasm with a not well-known and often aggressive biological behavior. Material and Methods We hereby describe 2 cases of cystic fibrosis patients who underwent bilateral sequential LT (BSLT) complicated by IMT. Results A 26-year-old man presented a right endobronchial lesion 6 months after BSLT. Two consecutive fiber bronchoscopic biopsies showed granulation tissue. For the persistent lesion growth, the patient underwent a transthoracic biopsy showing histologic diagnosis of IMT. Therefore, he underwent to right pneumonectomy that was unfortunately complicated after 6 months with a late bronchopleural fistula and empyema with exitus 6 months later. A 31-year-old woman 1 year after BSLT presented with a left voluminous pleural-parenchymal lesion; the histologic examination after biopsy revealed an IMT. She underwent a removal of the lesion with a macroscopic R0 resection. Histologic, immunophenotypic, and cytogenetic examinations showed a strong overexpression of anaplastic lymphoma kinase requiring biological adjuvant therapies; however, the patient refused it. Four years later, she presented a recurrence treated with debulking procedure and adjuvant radiotherapy. At last follow-up, the patient was alive with stable disease and optimal graft function. Conclusions Although IMT is a rare complication after lung transplant, to obtain a careful diagnosis, an early and aggressive treatment is mandatory

    Measurement of the Helicity Fractions of W Bosons from Top Quark Decays Using Fully Reconstructed top-antitop Events with CDF II

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    We present a measurement of the fractions F_0 and F_+ of longitudinally polarized and right-handed W bosons in top quark decays using data collected with the CDF II detector. The data set used in the analysis corresponds to an integrated luminosity of approximately 318 pb -1. We select ttbar candidate events with one lepton, at least four jets, and missing transverse energy. Our helicity measurement uses the decay angle theta*, which is defined as the angle between the momentum of the charged lepton in the W boson rest frame and the W momentum in the top quark rest frame. The cos(theta*) distribution in the data is determined by full kinematic reconstruction of the ttbar candidates. We find F_0 = 0.85 +0.15 -0.22 (stat) +- 0.06 (syst) and F_+ = 0.05 +0.11 -0.05 (stat) +- 0.03 (syst), which is consistent with the standard model prediction. We set an upper limit on the fraction of right-handed W bosons of F_+ < 0.26 at the 95% confidence level.Comment: 11 pages, 2 figures, submitted to Phys. Rev.

    Searches for Direct Pair Production of Supersymmetric Top and Supersymmetric Bottom Quarks in p-pbar Collisions at sqrt(s)=1.96 TeV

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    We search for direct pair production of supersymmetric top quarks and supersymmetric bottom quarks in proton-antiproton collisions at sqrt(s)=1.96 TeV, using 295 pb^-1 of data recorded by the Collider Detector at Fermilab (CDF II) experiment. The supersymmetric top (supersymmetric bottom) quarks are selected by reconstructing their decay into a charm (bottom) quark and a neutralino, which is assumed to be the lightest supersymmetric particle. The signature of such processes is two energetic heavy-flavor jets and missing transverse energy. The number of events that pass our selection for each search process is consistent with the expected standard model background. By comparing our results to the theoretical production cross sections of the supersymmetric top and supersymmetric bottom quarks in the minimal supersymmetric standard model, we exclude, at a 95% confidence level in the frame of that model, a supersymmetric top quark mass up to 132 GeV/c^2 for a neutralino mass of 48 GeV/c^2, and a supersymmetric bottom quark mass up to 193 GeV/c^2 for a neutralino mass of 40 GeV/c^2.Comment: 12 pages, 5 figures, submitted to Phys. Rev.

    Polarizations of J/psi and psi(2S) Mesons Produced in ppbar Collisions at 1.96 TeV

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    We have measured the polarizations of \jpsi and \psiprime mesons as functions of their transverse momentum \pt when they are produced promptly in the rapidity range ∣y∣<0.6|y|<0.6 with \pt \geq 5 \pgev. The analysis is performed using a data sample with an integrated luminosity of about 800 \ipb collected by the CDF II detector. For both vector mesons, we find that the polarizations become increasingly longitudinal as \pt increases from 5 to 30 \pgev. These results are compared to the predictions of nonrelativistic quantum chromodynamics and other contemporary models. The effective polarizations of \jpsi and \psiprime mesons from BB-hadron decays are also reported.Comment: 8 pages, 7 figures, published in Physical Review Letter

    Measurement of the top-quark mass using missing ETE_T+jets events with secondary vertex bb-tagging at CDF II

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    We present a measurement of the top-quark mass in ppˉp\bar p collisions at \hbox{s=1.96\sqrt{s}=1.96} TeV which uses events with an inclusive signature of missing transverse energy and jets. % The event selection is sensitive to ttˉ→W+bW−bˉ→lνbqq′bˉt\bar t\to W^+bW^-\bar b\to l\nu b q q^\prime \bar b independent of the lepton flavor, and results in a large acceptance for W→τνW\to\tau\nu decays. % All-hadronic ttˉt\bar t decays and events with identified electrons or muons are vetoed to provide a statistically independent sample with respect to all previous measurements. % The top-quark mass is inferred from the distribution of the scalar sum of all jet transverse energies and the missing transverse energy. Using 311 pb−1^{-1} of integrated luminosity recorded by the Collider Detector at Fermilab, we measure a top-quark mass mt=172.3−9.6+10.8m_t = 172.3 ^{+10.8}_{-9.6}(stat.)±10.8\pm 10.8(syst.) GeV/c2c^2. While the uncertainty on mtm_t is larger than that of other measurements, the result is statistically uncorrelated with those of other methods, and thus can help to reduce the overall mtm_t uncertainty when combined with other existing measurements.Comment: 8 pages, 4 figure

    Limits on Anomalous Triple Gauge Couplings in ppbar Collisions at sqrt{s}=1.96 TeV

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    We present a search for anomalous triple gauge couplings (ATGC) in WW and WZ boson production. The boson pairs are produced in ppbar collisions at sqrt{s}=1.96 TeV, and the data sample corresponds to 350 pb-1 of integrated luminosity collected with the CDF II detector at the Fermilab Tevatron. In this search one W decays to leptons, and the other boson (W or Z) decays hadronically. Combining with a previously published CDF measurement of Wgamma boson production yields ATGC limits of -0.18 < lambda < 0.17 and -0.46 < Delta kappa < 0.39 at the 95% confidence level, using a cut-off scale Lambda=1.5 TeV.Comment: 7 pages, 3 figures. Submitted to Phys. Rev.

    Precision measurement of the top quark mass from dilepton events at CDF II

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    We report a measurement of the top quark mass, M_t, in the dilepton decay channel of ttˉ→bℓ′+νℓ′bˉℓ−νˉℓt\bar{t}\to b\ell'^{+}\nu_{\ell'}\bar{b}\ell^{-}\bar{\nu}_{\ell} using an integrated luminosity of 1.0 fb^{-1} of p\bar{p} collisions collected with the CDF II detector. We apply a method that convolutes a leading-order matrix element with detector resolution functions to form event-by-event likelihoods; we have enhanced the leading-order description to describe the effects of initial-state radiation. The joint likelihood is the product of the likelihoods from 78 candidate events in this sample, which yields a measurement of M_{t} = 164.5 \pm 3.9(\textrm{stat.}) \pm 3.9(\textrm{syst.}) \mathrm{GeV}/c^2, the most precise measurement of M_t in the dilepton channel.Comment: 7 pages, 2 figures, version includes changes made prior to publication by journa

    Cross Section Measurements of High-pTp_T Dilepton Final-State Processes Using a Global Fitting Method

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    We present a new method for studying high-pTp_T dilepton events (e±e∓e^{\pm}e^{\mp}, μ±μ∓\mu^{\pm}\mu^{\mp}, e±μ∓e^{\pm}\mu^{\mp}) and simultaneously extracting the production cross sections of ppˉ→ttˉp\bar{p} \to t\bar{t}, ppˉ→W+W−p\bar{p} \to W^+W^-, and p\bar{p} \to \ztt at a center-of-mass energy of s=1.96\sqrt{s} = 1.96 TeV. We perform a likelihood fit to the dilepton data in a parameter space defined by the missing transverse energy and the number of jets in the event. Our results, which use 360pb−1360 {\rm pb^{-1}} of data recorded with the CDF II detector at the Fermilab Tevatron Collider, are σ(ttˉ)=8.5−2.2+2.7\sigma(t\bar{t}) = 8.5_{-2.2}^{+2.7} pb, σ(W+W−)=16.3−4.4+5.2\sigma(W^+W^-) = 16.3^{+5.2}_{-4.4} pb, and \sigma(\ztt) =291^{+50}_{-46} pb.Comment: 20 pages, 2 figures, to be submitted to PRD-R
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