12,304 research outputs found

    Decay of Bc+(3S)B+D0B_c^{*+}(3S) \to B^+D^0

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    The decay constant for the vector state of 3S3S-level in the heavy (bˉc)(\bar b c)-quarkonium is evaluated in the framework of sum rules for the mesonic currents. A scaling relation for the constants of vector quarkonia with different quark contents is derived. The numerical estime gives Γ(Bc+(3S)B+D0)=90±35\Gamma(B_c^{*+}(3S)\to B^+D^0)=90 \pm 35 MeV.Comment: 6 pages, Revte

    Photonic production of B_c-mesons

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    The cross section of the γγBc(Bc)bˉc\gamma \gamma \rightarrow B_c(B_c^*) \bar b c process is calculated. It is shown that near threshold the pseudoscalar state production is much suppressed with respect to the vector one. At large energies their ratio becaims σ(Bc)/sigma(Bc)4\sigma(B_c^*)/sigma(B_c)\sim 4. The process of heavy quark recombination dominates in the production of Bc(Bc)B_c(B_c^*) states. The fragmentation process bBcb\to B_c comes to play at high ptp_t values only, while its contribution will remain nondominant.Comment: Preprint IHEP 94-8

    f_B^{stat} and \mu_\pi^2 in quasiclassical approximation of sum rules

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    In the framework of sum rules with a use of quarkonium mass spectrum, evaluated in the quasiclassical approximation, estimates of leptonic constant fBstat320±60f_B^{stat}\simeq 320\pm 60 MeV in a static limit and for the average heavy quark momentum squared μπ20.5±0.1\mu_\pi^2 \simeq 0.5\pm 0.1 GeV2^2 are obtained.Comment: 7 pages, LATEX fil

    Activation and radiation damage in the environment of hadron accelerators

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    A component which suffers radiation damage usually also becomes radioactive, since the source of activation and radiation damage is the interaction of the material with particles from an accelerator or with reaction products. However, the underlying mechanisms of the two phenomena are different. These mechanisms are described here. Activation and radiation damage can have far-reaching consequences. Components such as targets, collimators, and beam dumps are the first candidates for failure as a result of radiation damage. This means that they have to be replaced or repaired. This takes time, during which personnel accumulate dose. If the dose to personnel at work would exceed permitted limits, remote handling becomes necessary. The remaining material has to be disposed of as radioactive waste, for which an elaborate procedure acceptable to the authorities is required. One of the requirements of the authorities is a complete nuclide inventory. The methods used for calculation of such inventories are presented, and the results are compared with measured data. In the second part of the paper, the effect of radiation damage on material properties is described. The mechanism of damage to a material due to irradiation is described. The amount of radiation damage is quantified in terms of displacements per atom. Its calculation and deficiencies in explaining and predicting the changes in mechanical and thermal material properties are discussed, and examples are given.Comment: 27 pages, contribution to the CAS - CERN Accelerator School: Course on High Power Hadron Machines; 24 May - 2 Jun 2011, Bilbao, Spai

    Hadronic resonance production with the ALICE experiment in pp and Pb-Pb collisions at LHC energies

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    Hadronic resonances K(892)0\mathrm{K}^{*}(892)^{0}, ϕ\phi(1020) and Σ(1385)±\Sigma(1385)^{\pm} have been measured by the ALICE experiment in pp collisions at s=7\sqrt{s}=7 TeV and in Pb-Pb collisions at sNN=2.76\sqrt{s_{_\mathrm{NN}}}=2.76 TeV. Transverse momentum spectra, particle ratios, nuclear modification factor and comparison with model predictions are discussed. In addition, ALICE results are compared with data obtained at RHIC energy.Comment: 3 pages, 3 figures, Proceedings of 16th Lomonosov Conference on Elementary Particle Physics, Moscow, 22/08/2013 - 28/08/201

    Absolutely continuous spectrum of perturbed Stark operators

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    We prove new results on the stability of the absolutely continuous spectrum for perturbed Stark operators with decaying or satisfying certain smoothness assumption perturbation. We show that the absolutely continuous spectrum of the Stark operator is stable if the perturbing potential decays at the rate (1+x)13ϵ(1+x)^{-\frac{1}{3}-\epsilon} or if it is continuously differentiable with derivative from the H\"older space Cα(R),C_{\alpha}(R), with any $\alpha>0.

    Regularity and blow up for active scalars

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    We review some recent results for a class of fluid mechanics equations called active scalars, with fractional dissipation. Our main examples are the surface quasi-geostrophic equation, the Burgers equation, and the Cordoba-Cordoba-Fontelos model. We discuss nonlocal maximum principle methods which allow to prove existence of global regular solutions for the critical dissipation. We also recall what is known about the possibility of finite time blow up in the supercritical regime.Comment: 33 page
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