64 research outputs found

    J/psi couplings to charmed resonances and to pi

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    We present an evaluation of the strong couplings JD^(*)D^(*) and JD^(*)D^(*)pi by an effective field theory of quarks and mesons. These couplings are necessary to calculate pi+J/psi --> D^(*)+barD^(*) cross sections, an important background to the J/psi suppression signal in the quark-gluon plasma. We write down the general effective lagrangian and compute the relevant couplings in the soft pion limit and beyond.Comment: 11 pages, 4 figures, 2 reference added and minor comments, style changed to RevTe

    On slip pulses at a sheared frictional viscoelastic/ non deformable interface

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    We study the possibility for a semi-infinite block of linear viscoelastic material, in homogeneous frictional contact with a non-deformable one, to slide under shear via a periodic set of ``self-healing pulses'', i.e. a set of drifting slip regions separated by stick ones. We show that, contrary to existing experimental indications, such a mode of frictional sliding is impossible for an interface obeying a simple local Coulomb law of solid friction. We then discuss possible physical improvements of the friction model which might open the possibility of such dynamics, among which slip weakening of the friction coefficient, and stress the interest of developing systematic experimental investigations of this question.Comment: 23 pages, 3 figures. submitted to PR

    Effects of Large CP violating phases on g_{\m}-2 in MSSM

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    Effects of CP violation on the supersymmetric electro-weak correction to the anomalous magnetic moment of the muon are investigated with the most general allowed set of CP violating phases in MSSM. The analysis includes contributions from the chargino and the neutralino exchanges to the muon anomaly. The supersymmetric contributions depend only on specific combinations of CP phases. The independent set of such phases is classified. We analyse the effects of the phases under the EDM constraints and show that large CP violating phases can drastically affect the magnitude of the supersymmetric electro-weak contribution to aÎŒa_{\mu} and may even affect its overall sign.Comment: 26 pages Latex file including 4 figure

    Gaugino Mass Nonuniversality and Dark Matter in SUGRA, Strings and D Brane Models

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    The effects of nonuniversality of gaugino masses on dark matter are examined within supersymmetric grand unification, and in string and D brane models with R parity invariance. In SU(5) unified models nonuniversality in the gaugino sector can be generated via the gauge kinetic energy function which may depend on the 24, 75 and 200 dimensional Higgs representations. We also consider string models which allow for nonuniversality of gaugino masses and D brane models where nonuniversality arises from embeddings of the Standard Model gauge group on five branes and nine branes. It is found that with gaugino mass nonuniversality the range of the LSP mass can be extended much beyond the range allowed in the universal SUGRA case, up to about 600 GeV even without coannihilation effects in some regions of the parameter space. The effects of coannihilation are not considered and inclusion of these effects may further increase the allowed neutralino mass range. Similarly with the inclusion of gaugino mass nonuniversality, the neutralino-proton (χ−p\chi -p) cross-section can increase by as much as a factor of 10 in some of regions of the parameter space. An analysis of the uncertainties in the quark density content of the nucleon is given and their effects on χ−p\chi -p cross-section are discussed. The predictions of our analysis including nonuniversality is compared with the current limits from dark matter detectors and implications for future dark matter searches are discussed.Comment: Revised version, 23 pages, Latex, and 7 figure

    Supersymmetric Dark Matter and Yukawa Unification

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    An analysis of supersymmetric dark matter under the Yukawa unification constraint is given. The analysis utilizes the recently discovered region of the parameter space of models with gaugino mass nonuniversalities where large negative supersymmetric corrections to the b quark mass appear to allow b−τb-\tau unification for a positive ÎŒ\mu sign consistent with the b→s+Îłb\to s+\gamma and gΌ−2g_{\mu}-2 constraints. In the present analysis we use the revised theoretical determination of aÎŒSMa_{\mu}^{SM} (aÎŒ=(gΌ−2)/2a_{\mu}= (g_{\mu}-2)/2) in computing the difference aÎŒexp−aÎŒSMa_{\mu}^{exp}-a_{\mu}^{SM} which takes account of a reevaluation of the light by light contribution which has a positive sign. The analysis shows that the region of the parameter space with nonuniversalities of the gaugino masses which allows for unification of Yukawa couplings also contains regions which allow satisfaction of the relic density constraint. Specifically we find that the lightest neutralino mass consistent with the relic density constraint, bτb\tau unification for SU(5) and b−t−τb-t-\tau unification for SO(10) in addition to other constraints lies in the region below 80 GeV. An analysis of the maximum and the minimum neutralino-proton scalar cross section for the allowed parameter space including the effect of a new determination of the pion-nucleon sigma term is also given. It is found that the full parameter space for this class of models can be explored in the next generation of proposed dark matter detectors.Comment: 28 pages,nLatex including 5 fig

    Association of Lupus Nephritis Histopathologic Classification With Venous Thromboembolism—Modification by Age at Biopsy

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    Introduction: Lupus nephritis (LN) is an independent risk factor for venous thromboembolism (VTE). The risk of VTE has not been analyzed by International Society of Nephrology/Renal Pathology Society or World Health Organization LN class. Study goals were to measure VTE incidence in an LN patient cohort, to evaluate associations between VTE and LN class, and to investigate factors modifying associations between VTE and LN class. Methods: A retrospective analysis was performed using Glomerular Disease Collaborative Network data. Image-confirmed VTE was compared between patients with any LN class V lesion and patients with only LN class III or IV. Logistic regression was used to calculate odds ratios and 95% confidence intervals. Effect modification was assessed between main effect and covariates. Results: Our cohort consisted of 534 LN patients, 310 (58%) with class III/IV and 224 (42%) with class V with or without class III/IV, including 106 with class V alone. The VTE incidence was 62 of 534 (11.6%). The odds of VTE were not significantly different between patients with class III/IV and class V in adjusted analyses (odds ratio [OR] = 0.82, 95% confidence interval [CI] = 0.45−1.48). An age interaction was observed (P = 0.009), with increased odds of VTE with class III/IV diagnosed at a younger age (2.75, 0.90−8.41 estimated at age 16 years) and decreased odds with class III/IV diagnosed at an older age (0.23, 0.07−0.72 estimated at age 46 years), compared to class V. Conclusions: The VTE incidence was similar among patients with LN classes III/IV and V, suggesting that VTE risk is not limited to class V−related nephrotic syndrome and that age may modulate LN class-specific VTE risk

    Measurement of the Spectroscopy of Orbitally Excited B Mesons at LEP

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    We measure the masses, decay widths and relative production rate of orbitally excited B mesons using 1.25 million hadronic Z decays recorded by the L3 detector. B-meson candidates are inclusively reconstructed and combined with charged pions produced at the primary event vertex. An excess of events above the expected background in the B\pi mass spectrum in the region 5.6-5.8 GeV is interpreted as resulting from the decay B_u,d^** -> B^(*)\pi, where B_u,d^** denotes a mixture of l=1 B-meson states containing a u or a d quark. A fit to the mass spectrum yields the masses and decay widths of the B_1^* and B_2^* spin states, as well as the branching fraction for the combination of l=1 states. In addition, evidence is presented for the existence of an excited B-meson state or mixture of states in the region 5.9-6.0 GeV

    Taming the terminological tempest in invasion science

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    Standardised terminology in science is important for clarity of interpretation and communication. In invasion science – a dynamic and rapidly evolving discipline – the proliferation of technical terminology has lacked a standardised framework for its development. The result is a convoluted and inconsistent usage of terminology, with various discrepancies in descriptions of damage and interventions. A standardised framework is therefore needed for a clear, universally applicable, and consistent terminology to promote more effective communication across researchers, stakeholders, and policymakers. Inconsistencies in terminology stem from the exponential increase in scientific publications on the patterns and processes of biological invasions authored by experts from various disciplines and countries since the 1990s, as well as publications by legislators and policymakers focusing on practical applications, regulations, and management of resources. Aligning and standardising terminology across stakeholders remains a challenge in invasion science. Here, we review and evaluate the multiple terms used in invasion science (e.g. ‘non-native’, ‘alien’, ‘invasive’ or ‘invader’, ‘exotic’, ‘non-indigenous’, ‘naturalised’, ‘pest’) to propose a more simplified and standardised terminology. The streamlined framework we propose and translate into 28 other languages is based on the terms (i) ‘non-native’, denoting species transported beyond their natural biogeographic range, (ii) ‘established non-native’, i.e. those non-native species that have established self-sustaining populations in their new location(s) in the wild, and (iii) ‘invasive non-native’ – populations of established non-native species that have recently spread or are spreading rapidly in their invaded range actively or passively with or without human mediation. We also highlight the importance of conceptualising ‘spread’ for classifying invasiveness and ‘impact’ for management. Finally, we propose a protocol for classifying populations based on (i) dispersal mechanism, (ii) species origin, (iii) population status, and (iv) impact. Collectively and without introducing new terminology, the framework that we present aims to facilitate effective communication and collaboration in invasion science and management of non-native species

    Sub-scalar reactions during oxidation of I-w-phase SiAlON glass-ceramics under a very low oxygen partial pressure

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    YSiAlON Iw glass–ceramic microstructures affected by surface oxidation during crystallisation have been compared with bulk microstructures which were unaffected by oxidation using transmission electron microscopy. The sub-scalar microstructures were found to have anomalously large Iw crystals (around twice the size of those in the unaffected bulk material), and some large γ and ή phase Y2Si2O7 crystals were also present. Compositional analysis using EDX and EELS showed that the composition of the Iw crystals was independent of their location below the oxidised surface, and that the N content of the Iw phase was significantly lower than previously believed, around 2 anion%. The residual glass composition in the sub-scalar volumes was more strongly affected by the diffusion processes occurring during oxidation, but in an inhomogeneous way. Areas mostly surrounded by Iw grains were little affected and showed little deviation of the N content from the average value for unaffected bulk residual glass of around 8 anion%. More open areas of sub-scalar glass, however, showed noticeably reduced N contents of less than 5 anion% N, and in some cases also an enrichment in Y. It was concluded that oxidation in the subscalar region is initiated mainly through diffusion in the more open areas of glass associated with an inward diffusion of O and the diffusion of cations leading to the local formation of Y2Si2O7 crystals
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