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

Leptonic and Semileptonic Decays of Charm and Bottom Hadrons

We review the experimental measurements and theoretical descriptions of leptonic and semileptonic decays of particles containing a single heavy quark, either charm or bottom. Measurements of bottom semileptonic decays are used to determine the magnitudes of two fundamental parameters of the standard model, the Cabibbo-Kobayashi-Maskawa matrix elements $V_{cb}$ and $V_{ub}$. These parameters are connected with the physics of quark flavor and mass, and they have important implications for the breakdown of CP symmetry. To extract precise values of $|V_{cb}|$ and $|V_{ub}|$ from measurements, however, requires a good understanding of the decay dynamics. Measurements of both charm and bottom decay distributions provide information on the interactions governing these processes. The underlying weak transition in each case is relatively simple, but the strong interactions that bind the quarks into hadrons introduce complications. We also discuss new theoretical approaches, especially heavy-quark effective theory and lattice QCD, which are providing insights and predictions now being tested by experiment. An international effort at many laboratories will rapidly advance knowledge of this physics during the next decade.Comment: This review article will be published in Reviews of Modern Physics in the fall, 1995. This file contains only the abstract and the table of contents. The full 168-page document including 47 figures is available at http://charm.physics.ucsb.edu/papers/slrevtex.p

Bottomonium and Drell-Yan production in p-A collisions at 450 GeV

The NA50 Collaboration has measured heavy-quarkonium production in p-A collisions at 450 GeV incident energy (sqrt(s) = 29.1 GeV). We report here results on the production of the Upsilon states and of high-mass Drell-Yan muon pairs (m > 6 GeV). The cross-section at midrapidity and the A-dependence of the measured yields are determined and compared with the results of other fixed-target experiments and with the available theoretical estimates. Finally, we also address some issues concerning the transverse momentum distributions of the measured dimuons.Comment: 18 pages, 9 figures, to be published in Phys. Lett.

Measurement of the Top Quark Pair Production Cross Section in pbarp Collisions

We present a measurement of the ttbar production cross section in ppbar collisions at root(s) = 1.8TeV by the D0 experiment at the Fermilab Tevatron. The measurement is based on data from an integrated luminosity of approximately 125 pb^-1 accumulated during the 1992-1996 collider run. We observe 39 ttbar candidate events in the dilepton and lepton+jets decay channels with an expected background of 13.7+-2.2 events. For a top quark mass of 173.3GeV/c^2, we measure the ttbar production cross section to be 5.5+-1.8 pb.Comment: 11 pages with 3 encapsulated PostScript figures and 2 PostScript table included in the body of the articl

Top-ology

Extended version of an article on top-quark physics, to appear in the May 1997 issue of Physics Today.Comment: 24 pages, 5 figures, LaTeX2e + BoxedEPS

The genomes of two key bumblebee species with primitive eusocial organization

Background: The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. High-quality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats. Results: We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits. Conclusions: These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation

Reforming Fiscal Institutions in Resource-Rich Arab Economies: Policy Proposals

This paper traces the evolution of fiscal institutions of Resource Rich Arab Economies (RRAEs) over time since their pre-oil days, through the discovery of oil to their build-up of oil exports. It then identifies challenges faced by RRAEs and variations in their severity among the different countries over time. Finally, it articulates specific policy reforms, which, if implemented successfully, could help to overcome these challenges. In some cases, however, these policy proposals may give rise to important trade-offs that will have to be evaluated carefully in individual cases

New Petro‐aggression in the Middle East: Saudi Arabia in the Spotlight

That hydrocarbon abundance may lead to more violence is an established truism in the literature on the resource curse. Looking at the Middle East, however, the literature relates bellicose state behaviour entirely to oil-producing revolutionary republics. Instead, dynastic monarchies are claimed to be the more peacefully behaving actors. Current developments turn this conclusion upside down, however. Since 2015 at the latest, the foreign policy of Saudi Arabia, the leading monarchy in the Middle East, has transformed from multi-dependence to petro-aggression. By discussing this striking transformation, the paper puts forward a framework looking at the interaction of three crucial dimensions: first, the decreasing power projection towards the Middle East by the United States, the decade-long hegemon, due to gradual changes in world energy markets and war fatigue at home; second, the lasting fiscal potency of the Saudi regime; and, third, the personalization of the Saudi monarchy under King Salman as a historically contingent result of transferring power to the generation of Ibn Saud's grandsons