Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s) = 1.96 TeV

We present a measurement of the top quark pair production cross section in ppbar collisions at sqrt(s)=1.96 TeV using 318 pb^{-1} of data collected with the Collider Detector at Fermilab. We select ttbar decays into the final states e nu + jets and mu nu + jets, in which at least one b quark from the t-quark decays is identified using a secondary vertex-finding algorithm. Assuming a top quark mass of 178 GeV/c^2, we measure a cross section of 8.7 +-0.9 (stat) +1.1-0.9 (syst) pb. We also report the first observation of ttbar with significance greater than 5 sigma in the subsample in which both b quarks are identified, corresponding to a cross section of 10.1 +1.6-1.4(stat)+2.0-1.3 (syst) pb.Comment: Accepted for publication in Physics Review Letters, 7 page

Search for Second-Generation Scalar Leptoquarks in ppˉ\bm{p \bar{p}} Collisions at s\sqrt{s}=1.96 TeV

Results on a search for pair production of second generation scalar leptoquark in $p \bar{p}$ collisions at $\sqrt{s}$=1.96 TeV 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 198 pb$^{-1}$. 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 $\beta$, where $\beta$ is the branching fraction for $LQ \to \mu q$.Comment: 9 pages (3 author list) 5 figure

Determination of the Jet Energy Scale at the Collider Detector at Fermilab

A precise determination of the energy scale of jets at the Collider Detector at Fermilab at the Tevatron $p\bar{p}$ collider is described. Jets are used in many analyses to estimate the energies of partons resulting from the underlying physics process. Several correction factors are developed to estimate the original parton energy from the observed jet energy in the calorimeter. The jet energy response is compared between data and Monte Carlo simulation for various physics processes, and systematic uncertainties on the jet energy scale are determined. For jets with transverse momenta above 50 GeV the jet energy scale is determined with a 3% systematic uncertainty

Mortality after coronary artery bypass grafting versus percutaneous coronary intervention with stenting for coronary artery disease: a pooled analysis of individual patient data

Background: Numerous randomised trials have compared coronary artery bypass grafting (CABG) with percutaneous coronary intervention (PCI) for patients with coronary artery disease. However, no studies have been powered to detect a difference in mortality between the revascularisation strategies. Methods: We did a systematic review up to July 19, 2017, to identify randomised clinical trials comparing CABG with PCI using stents. Eligible studies included patients with multivessel or left main coronary artery disease who did not present with acute myocardial infarction, did PCI with stents (bare-metal or drug-eluting), and had more than 1 year of follow-up for all-cause mortality. In a collaborative, pooled analysis of individual patient data from the identified trials, we estimated all-cause mortality up to 5 years using Kaplan-Meier analyses and compared PCI with CABG using a random-effects Cox proportional-hazards model stratified by trial. Consistency of treatment effect was explored in subgroup analyses, with subgroups defined according to baseline clinical and anatomical characteristics. Findings: We included 11 randomised trials involving 11 518 patients selected by heart teams who were assigned to PCI (n=5753) or to CABG (n=5765). 976 patients died over a mean follow-up of 3·8 years (SD 1·4). Mean Synergy between PCI with Taxus and Cardiac Surgery (SYNTAX) score was 26·0 (SD 9·5), with 1798 (22·1%) of 8138 patients having a SYNTAX score of 33 or higher. 5 year all-cause mortality was 11·2% after PCI and 9·2% after CABG (hazard ratio [HR] 1·20, 95% CI 1·06–1·37; p=0·0038). 5 year all-cause mortality was significantly different between the interventions in patients with multivessel disease (11·5% after PCI vs 8·9% after CABG; HR 1·28, 95% CI 1·09–1·49; p=0·0019), including in those with diabetes (15·5% vs 10·0%; 1·48, 1·19–1·84; p=0·0004), but not in those without diabetes (8·7% vs 8·0%; 1·08, 0·86–1·36; p=0·49). SYNTAX score had a significant effect on the difference between the interventions in multivessel disease. 5 year all-cause mortality was similar between the interventions in patients with left main disease (10·7% after PCI vs 10·5% after CABG; 1·07, 0·87–1·33; p=0·52), regardless of diabetes status and SYNTAX score. Interpretation: CABG had a mortality benefit over PCI in patients with multivessel disease, particularly those with diabetes and higher coronary complexity. No benefit for CABG over PCI was seen in patients with left main disease. Longer follow-up is needed to better define mortality differences between the revascularisation strategies

Measurement of the Dipion Mass Spectrum in X(3872) -> J/Psi Pi+ Pi- Decays

We measure the dipion mass spectrum in X(3872)--> J/Psi Pi+ Pi- decays using 360 pb-1 of pbar-p collisions at 1.96 TeV collected with the CDF II detector. The spectrum is fit with predictions for odd C-parity (3S1, 1P1, and 3DJ) charmonia decaying to J/Psi Pi+ Pi-, as well as even C-parity states in which the pions are from Rho0 decay. The latter case also encompasses exotic interpretations, such as a D0-D*0Bar molecule. Only the 3S1 and J/Psi Rho hypotheses are compatible with our data. Since 3S1 is untenable on other grounds, decay via J/Psi Rho is favored, which implies C=+1 for the X(3872). Models for different J/Psi-Rho angular momenta L are considered. Flexibility in the models, especially the introduction of Rho-Omega interference, enable good descriptions of our data for both L=0 and 1.Comment: 7 pages, 4 figures -- Submitted to Phys. Rev. Let

Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s}=1.96 TeV using Lepton + Jets Events with Secondary Vertex b-tagging

We present a measurement of the ttbar production cross section using events with one charged lepton and jets from ppbar 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 ttbar production cross section of 5.6^{+1.2}_{-1.1} (stat.) ^{+0.9}_{0.6} (syst.) pb.Comment: 28 pages, 20 figures. Published in Physical Review

Search for ZZ and ZW Production in ppbar Collisions at sqrt(s) = 1.96 TeV

We present a search for ZZ and ZW vector boson pair production in ppbar collisions at sqrt(s) = 1.96 TeV using the leptonic decay channels ZZ --> ll nu nu, ZZ --> l l l' l' and ZW --> l l l' nu. In a data sample corresponding to an integrated luminosity of 194 pb-1 collected with the Collider Detector at Fermilab, 3 candidate events are found with an expected background of 1.0 +/- 0.2 events. We set a 95% confidence level upper limit of 15.2 pb on the cross section for ZZ plus ZW production, compared to the standard model prediction of 5.0 +/- 0.4 pb.Comment: 7 pages, 2 figures. This version is accepted for publication by Phys. Rev. D Rapid Communication

Search for New Physics in Lepton + Photon + X Events with L=305 pb-1 of ppbar Collisions at roots=1.96 TeV

We present results of a search for anomalous production of events containing a charged lepton (either electron or muon) and a photon, both with high transverse momentum, accompanied by additional signatures, X, including missing transverse energy (MET) and additional leptons and photons. We use the same kinematic selection criteria as in a previous CDF search, but with a substantially larger data set, 305 pb-1, a ppbar collision energy of 1.96 TeV, and the upgraded CDF II detector. We find 42 Lepton+Photon+MET events versus a standard model expectation of 37.3 +- 5.4 events. The level of excess observed in Run I, 16 events with an expectation of 7.6 +- 0.7 events (corresponding to a 2.7 sigma effect), is not supported by the new data. In the signature of Multi-Lepton+Photon+X we observe 31 events versus an expectation of 23.0 +- 2.7 events. In this sample we find no events with an extra photon or MET and so find no events like the one ee+gg+MET event observed in Run I.Comment: 7 pages, 3 figures, 1 table. Accepted to PR

Development and characterisation of a large diameter decellularised vascular allograft

The aims of this study were to develop a biological large diameter vascular graft by decellularisation of native human aorta to remove the immunogenic cells whilst retaining the essential biomechanical, and biochemical properties for the ultimate benefit of patients with infected synthetic grafts. Donor aortas (n = 6) were subjected to an adaptation of a propriety decellularisation process to remove the cells and acellularity assessed by histological analysis and extraction and quantification of total DNA. The biocompatibility of the acellular aortas was determined using standard contact cytotoxicity tests. Collagen and denatured collagen content of aortas was determined and immunohistochemistry was used to determine the presence of specific extracellular matrix proteins. Donor aortas (n = 6) were divided into two, with one half subject to decellularisation and the other half retained as native tissue. The native and decellularised aorta sections were then subject to uniaxial tensile testing to failure [axial and circumferential directions] and suture retention testing. The data was compared using a paired t-test. Histological evaluation showed an absence of cells in the treated aortas and retention of histoarchitecture including elastin content. The decellularised aortas had less than 15 ng mg¯¹ total DNA per dry weight (mean 94% reduction) and were biocompatible as determined by in vitro contact cytotoxicity tests. There were no gross changes in the histoarchitecture [elastin and collagen matrix] of the acellular aortas compared to native controls. The decellularisation process also reduced calcium deposits within the tissue. The uniaxial tensile and suture retention testing revealed no significant differences in the material properties (p > 0.05) of decellularised aorta. The decellularisation procedure resulted in minimal changes to the biological and biomechanical properties of the donor aortas. Acellular donor aorta has excellent potential for use as a large diameter vascular graft