12,304 research outputs found

### Decay of $B_c^{*+}(3S) \to B^+D^0$

The decay constant for the vector state of $3S$-level in the heavy $(\bar b
c)$-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
$\Gamma(B_c^{*+}(3S)\to B^+D^0)=90 \pm 35$ MeV.Comment: 6 pages, Revte

### Photonic production of B_c-mesons

The cross section of the $\gamma \gamma \rightarrow B_c(B_c^*) \bar b c$
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 $\sigma(B_c^*)/sigma(B_c)\sim 4$. The process of heavy
quark recombination dominates in the production of $B_c(B_c^*)$ states. The
fragmentation process $b\to B_c$ comes to play at high $p_t$ 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

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

### Activation and radiation damage in the environment of hadron accelerators

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

Hadronic resonances $\mathrm{K}^{*}(892)^{0}$, $\phi$(1020) and
$\Sigma(1385)^{\pm}$ have been measured by the ALICE experiment in pp
collisions at $\sqrt{s}=7$ TeV and in Pb-Pb collisions at
$\sqrt{s_{_\mathrm{NN}}}=2.76$ 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

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
$(1+x)^{-\frac{1}{3}-\epsilon}$ or if it is continuously differentiable with
derivative from the H\"older space $C_{\alpha}(R),$ with any $\alpha>0.

### Regularity and blow up for active scalars

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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