Optimized 4 pi spherical shell depleted uranium-water shield weights for 200 to 550-megawatt reactors

Optimization calculations to determine minimum 4 pi spherical-shell weights were performed at 200-, 375-, and 550-megawatt-thermal reactor power levels. Monte Carlo analyses were performed for a reactor power level corresponding to 375 megawatts. Power densities for the spherical reactor model used varied from 64.2 to 256 watts per cubic centimeter. The dose rate constraint in the optimization calculations was 0.25 mrem per hour at 9.14 meters from the reactor center. The resulting shield weights were correlated with the reactor power levels and power densities by a regression analysis. The optimum shield weight for a 375-megawatt, 160-watt-per-cubic-centimeter reactor was 202,000 kilograms

Noncompaction cardiomyopathy and heterotaxy syndrome

Left ventricular noncompaction cardiomyopathy (LVNC) is characterized by compact and trabecular layers of the left ventricular myocardium. This cardiomyopathy may occur with congenital heart disease (CHD). Single cases document co-occurrence of LVNC and heterotaxy, but no data exist regarding the prevalence of this association. This study sought to determine whether a non-random association of LVNC and heterotaxy exists by evaluating the prevalence of LVNC in patients with heterotaxy. In a retrospective review of the Indiana Network for Patient Care, we identified 172 patients with heterotaxy (69 male, 103 female). Echocardiography and cardiac magnetic resonance imaging results were independently reviewed by two cardiologists to ensure reproducibility of LVNC. A total of 13/172 (7.5%) patients met imaging criteria for LVNC. The CHD identified in this subgroup included atrioventricular septal defects [11], dextrocardia [10], systemic and pulmonary venous return abnormalities [7], and transposition of the great arteries [5]. From this subgroup, 61% (n = 8) of the patients developed arrhythmias; and 61% (n = 8) required medical management for chronic heart failure. This study indicates that LVNC has increased prevalence among patients with heterotaxy when compared to the general population (0.014–1.3%) suggesting possible common genetic mechanisms. Interestingly, mice with a loss of function of Scrib or Vangl2 genes showed abnormal compaction of the ventricles, anomalies in cardiac looping, and septation defects in previous studies. Recognition of the association between LVNC and heterotaxy is important for various reasons. First, the increased risk of arrhythmias demonstrated in our population. Secondly, theoretical risk of thromboembolic events remains in any LVNC population. Finally, many patients with heterotaxy undergo cardiac surgery (corrective and palliative) and when this is associated with LVNC, patients should be presumed to incur a higher peri-operative morbidity based on previous studies. Further research will continue to determine long-term and to corroborate genetic pathways

Factorization and Scaling in Hadronic Diffraction

In standard Regge theory with a pomeron intercept a(0)=1+\epsilon, the contribution of the tripe-pomeron amplitude to the t=0 differential cross section for single diffraction dissociation has the form d\sigma/dM^2(t=0) \sim s^{2\epsilon}/(M^2)^{1+\epsilon}. For \epsilon>0, this form, which is based on factorization, does not scale with energy. From an analysis of p-p and p-pbar data from fixed target to collider energies, we find that such scaling actually holds, signaling a breakdown of factorization. Phenomenologically, this result can be obtained from a scaling law in diffraction, which is embedded in the hypothesis of pomeron flux renormalization introduced to unitarize the triple pomeron amplitude.Comment: 39 pages, Latex, 16 figure

Measurement of the WW Boson Mass

A measurement of the mass of the $W$ boson is presented based on a sample of 5982 $W \rightarrow e \nu$ decays observed in $p\overline{p}$ collisions at $\sqrt{s}$ = 1.8~TeV with the D\O\ detector during the 1992--1993 run. From a fit to the transverse mass spectrum, combined with measurements of the $Z$ boson mass, the $W$ boson mass is measured to be $M_W = 80.350 \pm 0.140 (stat.) \pm 0.165 (syst.) \pm 0.160 (scale) GeV/c^2$.Comment: 12 pages, LaTex, style Revtex, including 3 postscript figures (submitted to PRL

Search for Top Squark Pair Production in the Dielectron Channel

This report describes the first search for top squark pair production in the channel stop_1 stopbar_1 -> b bbar chargino_1 chargino_1 -> ee+jets+MEt using 74.9 +- 8.9 pb^-1 of data collected using the D0 detector. A 95% confidence level upper limit on sigma*B is presented. The limit is above the theoretical expectation for sigma*B for this process, but does show the sensitivity of the current D0 data set to a particular topology for new physics.Comment: Five pages, including three figures, submitted to PRD Brief Report

Search for First Generation Scalar Leptoquark Pairs in ppbar Collisions at sqrt(s)=1.8 TeV

We have searched for first generation scalar leptoquark (LQ) pairs in the enu+jets channel using ppbar collider data (integrated luminosity= 115 pb^-1) collected by the DZero experiment at the Fermilab Tevatron during 1992-96. The analysis yields no candidate events. We combine the results with those from the ee+jets and nunu+jets channels to obtain 95% confidence level (CL) upper limits on the LQ pair production cross section as a function of mass and of beta, the branching fraction to a charged lepton. Comparing with the next-to-leading order theory, we set 95% CL lower limits on the LQ mass of 225, 204, and 79 GeV/c^2 for beta=1, 1/2, and 0, respectively.Comment: 14 pages, 4 figures, submitted to Physical Review Letters Replaced to correct visitor addresse

Limits on Anomalous WWgamma and WWZ Couplings

Limits on the anomalous WWgamma and WWZ couplings are presented from a simultaneous fit to the data samples of three gauge boson pair final states in pbar-p collisions at sqrt(s)=1.8 TeV: Wgamma production with the W boson decaying to enu or munu, W boson pair production with both of the W bosons decaying to enu or munu, and WW or WZ production with one W boson decaying to enu and the other W boson or the Z boson decaying to two jets. Assuming identical WWgamma and WWZ couplings, 95 % C.L. limits on the anomalous couplings of -0.30<Delta kappa<0.43 (lambda = 0) and -0.20<lambda<0.20 (Delta kappa = 0) are obtained using a form factor scale Lambda = 2.0 TeV. Limits found under other assumptions on the relationship between the WWgamma and WWZ couplings are also presented.Comment: 13 pages, 3 figures, submitted to Physical Review

Second Generation Leptoquark Search in p\bar{p} Collisions at s\sqrt{s} = 1.8 TeV

We report on a search for second generation leptoquarks with the D\O\ detector at the Fermilab Tevatron $p\bar{p}$ collider at $\sqrt{s}$ = 1.8 TeV. This search is based on 12.7 pb$^{-1}$ of data. Second generation leptoquarks are assumed to be produced in pairs and to decay into a muon and quark with branching ratio $\beta$ or to neutrino and quark with branching ratio $(1-\beta)$. We obtain cross section times branching ratio limits as a function of leptoquark mass and set a lower limit on the leptoquark mass of 111 GeV/c$^{2}$ for $\beta = 1$ and 89 GeV/c$^{2}$ for $\beta = 0.5$ at the 95%\ confidence level.Comment: 18 pages, FERMILAB-PUB-95/185-

Measurement of Dijet Angular Distributions and Search for Quark Compositeness

We have measured the dijet angular distribution in $\sqrt{s}$=1.8 TeV $p\bar{p}$ collisions using the D0 detector. Order $\alpha^{3}_{s}$ QCD predictions are in good agreement with the data. At 95% confidence the data exclude models of quark compositeness in which the contact interaction scale is below 2 TeV.Comment: 11 pages, Latex, 3 postscript figure

Jet Production via Strongly-Interacting Color-Singlet Exchange in ppˉp\bar{p} Collisions

A study of the particle multiplicity between jets with large rapidity separation has been performed using the D{\O}detector at the Fermilab Tevatron $p\bar{p}$ Collider operating at $\sqrt{s}=1.8$ TeV. A significant excess of low-multiplicity events is observed above the expectation for color-exchange processes. The measured fractional excess is $1.07 \pm 0.10({\rm stat})^{+ 0.25}_{- 0.13}({\rm syst})$, which is consistent with a strongly-interacting color-singlet (colorless) exchange process and cannot be explained by electroweak exchange alone. A lower limit of 0.80% (95% C.L.) is obtained on the fraction of dijet events with color-singlet exchange, independent of the rapidity gap survival probability.Comment: 15 pages (REVTeX), 3 PS figs (uuencoded/tar compressed, epsf.sty) Complete postscript available at http://d0sgi0.fnal.gov/d0pubs/journals.html Submitted to Physical Review Letter