Search results for "Particle physics"
showing 10 items of 6826 documents
PREDICTION OF HIDDEN CHARM BARYONS WITH HEAVY QUARK SPIN AND LOCAL HIDDEN GAUGE SYMMETRIES
2014
In our talk, we explore a coupled channel unitary approach to investigate the meson baryon interaction with hidden charm, using constraints of heavy quark spin symmetry. With the full space of states demanded by the heavy quark spin symmetry and the dynamics of the local hidden gauge, we find four basic states which are bound by about 50 MeV with respect to the corresponding [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] thresholds respectively and decay mostly into ηcN and J/ψN. All the states appear in isospin I = 1/2, some of which are degenerated in different momentum J.
From supersymmetric to non-supersymmetric black holes
2012
Methods similar to those used for obtaining supersymmetric black hole solutions can be employed to find also non-supersymmetric solutions. We briefly review some of them, with the emphasis on the non-extremal deformation ansatz of [1].
Three-body forces in the quark model
2008
The constituent quark model has been very useful for the description of many physical properties of baryons, achieving in most cases a fair agreement with the experimental data 1 The model is based on a non relativistic QCD-inspired dynamics including a harmonic oscillator (h.o.) confinement potential and a spin dependent (hyperfine) interaction. The use of Lovelace coordinates p, ~ avoides any problem with the center of mass motion, while the h.o. potential provides a simple basis for ana ly t ica l calculations, which is a very important feature for many applications, like the evaluation of form factors and Meson Exchange Currents 2. On the other hand the h.o. spectrum is too degenerate w…
A powerful hydrodynamic booster for relativistic jets
2006
Velocities close to the speed of light are a robust observational property of the jets observed in microquasars and AGNs, and are expected to be behind much of the phenomenology of GRBs. Yet, the mechanism boosting relativistic jets to such large Lorentz factors is still essentially unknown. Building on recent general-relativistic, multidimensional simulations of progenitors of short GRBs, we discuss a new effect in relativistic hydrodynamics which can act as an efficient booster in jets. This effect is purely hydrodynamical and occurs when large velocities tangential to a discontinuity are present in the flow, yielding Lorentz factors $\Gamma \sim 10^2-10^3$ or larger in flows with moderat…
First Imaging of Coronal Mass Ejections in the Heliosphere Viewed from Outside the Sun – Earth Line
2007
We show for the first time images of solar coronal mass ejections (CMEs) viewed using the Heliospheric Imager (HI) instrument aboard the NASA STEREO spacecraft. The HI instruments are wide-angle imaging systems designed to detect CMEs in the heliosphere, in particular, for the first time, observing the propagation of such events along the Sun – Earth line, that is, those directed towards Earth. At the time of writing the STEREO spacecraft are still close to the Earth and the full advantage of the HI dual-imaging has yet to be realised. However, even these early results show that despite severe technical challenges in their design and implementation, the HI instruments can successfully detec…
The MEGA project
2004
Abstract We describe the development of a new telescope for Medium Energy Gamma-Ray Astronomy (MEGA) for the energy band 0.4–50 MeV. As a successor to COMPTEL and EGRET (low energies), MEGA aims to improve the sensitivity for astronomical sources by at least an order of magnitude. It could thus fill the severe sensitivity gap between scheduled or operating hard-X-ray and high-energy γ-ray missions and open the way for a future Advanced Compton Telescope. MEGA records and images γ-rays by completely tracking Compton and Pair creation events in a stack of double sided Si-strip track detectors surrounded by a pixelated CsI calorimeter. A scaled down prototype has been built and calibrations us…
The effective neutrino charge radius
2003
It is shown that at one-loop order a neutrino charge radius (NCR) may be defined, which is ultraviolet finite, does not depend on the gauge-fixing parameter, nor on properties of the target other than its electric charge. This is accomplished through the systematic decomposition of physical amplitudes into effective self-energies, vertices, and boxes, which separately respect electroweak gauge invariance. In this way the NCR stems solely from an effective proper photon-neutrino one-loop vertex, which satisfies a naive, QED-like Ward identity. The NCR so defined may be extracted from experiment, at least in principle, by expressing a set of experimental electron-neutrino cross-sections in te…
Singular Extremals for the Time-Optimal Control of Dissipative Spin 1/2 Particles
2010
We consider the time-optimal control by magnetic fields of a spin 1/2 particle in a dissipative environment. This system is used as an illustrative example to show the role of singular extremals in the control of quantum systems. We analyze a simple case where the control law is explicitly determined. We experimentally implement the optimal control using techniques of nuclear magnetic resonance. To our knowledge, this is the first experimental demonstration of singular extremals in quantum systems with bounded control amplitudes.
Improved unitarized heavy baryon chiral perturbation theory for πN scattering to fourth order
2004
We extend our previous analysis of the unitarized pion-nucleon scattering amplitude including up to fourth order terms in heavy baryon chiral perturbation theory. We pay special attention to the stability of the generated Delta(1232) resonance, the convergence problems, and the power counting of the chiral parameters.
The chiral anomaly in non-leptonic weak interactions
1992
7 páginas.-- arXiv:hep-ph/9205210v1