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

The Joint European Compound Library:boosting precompetitive research

The Joint European Compound Library (JECL) is a new high-throughput screening collection aimed at driving precompetitive drug discovery and target validation. The JECL has been established with a core of over 321000 compounds from the proprietary collections of seven pharmaceutical companies and will expand to around 500000 compounds. Here, we analyse the physicochemical profile and chemical diversity of the core collection, showing that the collection is diverse and has a broad spectrum of predicted biological activity. We also describe a model for sharing compound information from multiple proprietary collections, enabling diversity and quality analysis without disclosing structures. The JECL is available for screening at no cost to European academic laboratories and SMEs through the IMI European Lead Factory (http://www.europeanleadfactory.eu/)

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

Kinematic Effects in Radiative Quarkonia Decays

Non-relativistic QCD (NRQCD) predicts colour octet contributions to be significant not only in many production processes of heavy quarkonia but also in their radiative decays. We investigate the photon energy distributions in these processes in the endpoint region. There the velocity expansion of NRQCD breaks down which requires a resummation of an infinite class of colour octet operators to so-called shape functions. We model these non-perturbative functions by the emission of a soft gluon cluster in the initial state. We found that the spectrum in the endpoint region is poorly understood if the values for the colour octet matrix elements are taken as large as indicated from NRQCD scaling rules. Therefore the endpoint region should not be taken into account for a fit of the strong coupling constant at the scale of the heavy quark mass.Comment: LaTeX, 17 pages, 5 figures. The complete paper is also available via the www at http://www-ttp.physik.uni-karlsruhe.de/Preprints

Colour-Octet Effects in Radiative Υ\Upsilon Decays

We investigate the effects of colour-octet contributions to the radiative $\Upsilon$ decay within the Bodwin, Braaten and Lepage NRQCD factorization framework. Photons coming both from the coupling to hard processes (`direct') and by collinear emission from light quarks (`fragmentation') are consistently included at next-to-leading order (NLO) in $\alpha_s$. An estimate for the non-perturbative matrix elements which enter in the final result is then obtained. By comparing the NRQCD prediction at NLO for total decay rates with the experimental data, it is found that the non-perturbative parameters must be smaller than expected from the na\"\i ve scaling rules of NRQCD. Nevertheless, colour-octet contributions to the shape of the photon spectrum turn out to be significant.Comment: 25 pages, Latex, 8 figure

Diffractive Dissociation and Eikonalization in High Energy pp and p pˉ {\bar p} Collisions

We show that eikonal corrections imposed on diffraction dissociation processes calculated in the triple Regge limit, produce a radical change in the energy dependence of the predicted cross section. The induced correction is shown to be in general agreement with the new experimental data measured at the Tevatron.Comment: 11 pages LATEX, ( two figures not included obtainable from authors) (TAUP 2066-93 and FERMILAB PUB 93/ T

Diffractive Dissociation In The Interacting Gluon Model

We have extended the Interacting Gluon Model (IGM) to calculate diffractive mass spectra generated in hadronic collisions. We show that it is possible to treat both diffractive and non-diffractive events on the same footing, in terms of gluon-gluon collisions. A systematic analysis of available data is performed. The energy dependence of diffractive mass spectra is addressed. They show a moderate narrowing at increasing energies. Predictions for LHC energies are presented.Comment: 12 pages, latex, 14 figures (PostScript Files included); accepted for publication in Phys. Rev. D (Feb.97

A measurement of the W boson mass using large rapidity electrons

We present a measurement of the W boson mass using data collected by the D0 experiment at the Fermilab Tevatron during 1994--1995. We identify W bosons by their decays to e-nu final states where the electron is detected in a forward calorimeter. We extract the W boson mass, Mw, by fitting the transverse mass and transverse electron and neutrino momentum spectra from a sample of 11,089 W -> e nu decay candidates. We use a sample of 1,687 dielectron events, mostly due to Z -> ee decays, to constrain our model of the detector response. Using the forward calorimeter data, we measure Mw = 80.691 +- 0.227 GeV. Combining the forward calorimeter measurements with our previously published central calorimeter results, we obtain Mw = 80.482 +- 0.091 GeV

Search for Squarks and Gluinos in Events Containing Jets and a Large Imbalance in Transverse Energy

Using data corresponding to an integrated luminosity of 79 pb-1, D0 has searched for events containing multiple jets and large missing transverse energy in pbar-p collisions at sqrt(s)=1.8 TeV at the Fermilab Tevatron collider. Observing no significant excess beyond what is expected from the standard model, we set limits on the masses of squarks and gluinos and on the model parameters m_0 and m_1/2, in the framework of the minimal low-energy supergravity models of supersymmetry. For tan(beta) = 2 and A_0 = 0, with mu < 0, we exclude all models with m_squark < 250 GeV/c^2. For models with equal squark and gluino masses, we exclude m < 260 GeV/c^2.Comment: 10 pages, 3 figures, Submitted to PRL, Fixed typo on page bottom of p. 6 (QCD multijet background is 35.4 events

Precise measurement of the top quark mass in the dilepton channel at D0

We measure the top quark mass (mt) in ppbar collisions at a center of mass energy of 1.96 TeV using dilepton ttbar->W+bW-bbar->l+nubl-nubarbbar events, where l denotes an electron, a muon, or a tau that decays leptonically. The data correspond to an integrated luminosity of 5.4 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider. We obtain mt = 174.0 +- 1.8(stat) +- 2.4(syst) GeV, which is in agreement with the current world average mt = 173.3 +- 1.1 GeV. This is currently the most precise measurement of mt in the dilepton channel.Comment: 7 pages, 4 figure