Phi_2 (alpha) measurement using B -> rho pi decays at Belle

We present measurements of time-dependent asymmetries in decays of neutral B mesons to the final states B0 -> rho+ pi-. Measurements are based on a 140 fb-1 data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.Comment: 7 pages, 4 figures, contribution to the 32nd International Conference on High Energy Physics (ICHEP'04), August 2004, Beijing, Chin

Indeterminacy and instability in Petschek reconnection

We explain two puzzling aspects of Petschek's model for fast reconnection. One is its failure to occur in plasma simulations with uniform resistivity. The other is its inability to provide anything more than an upper limit for the reconnection rate. We have found that previously published analytical solutions based on Petschek's model are structurally unstable if the electrical resistivity is uniform. The structural instability is associated with the presence of an essential singularity at the X-line that is unphysical. By requiring that such a singularity does not exist, we obtain a formula that predicts a specific rate of reconnection. For uniform resistivity, reconnection can only occur at the slow, Sweet-Parker rate. For nonuniform resistivity, reconnection can occur at a much faster rate provided that the resistivity profile is not too flat near the X-line. If this condition is satisfied, then the scale length of the nonuniformity determines the reconnection rate

Observation of "Topological" Microflares in the Solar Atmosphere

We report on observation of the unusual kind of solar microflares, presumably associated with the so-called "topological trigger" of magnetic reconnection, which was theoretically suggested long time ago by Gorbachev et al. (Sov. Ast. 1988, v.32, p.308) but has not been clearly identified so far by observations. As can be seen in pictures by Hinode SOT in CaII line, there may be a bright loop connecting two sunspots, which looks at the first sight just as a magnetic field line connecting the opposite poles. However, a closer inspection of SDO HMI magnetograms shows that the respective arc is anchored in the regions of the same polarity near the sunspot boundaries. Yet another peculiar feature is that the arc flashes almost instantly as a thin strip and then begins to expand and decay, while the typical chromospheric flares in CaII line are much wider and propagate progressively in space. A qualitative explanation of the unusual flare can be given by the above-mentioned model of topological trigger. Namely, there are such configurations of the magnetic sources on the surface of photosphere that their tiny displacements result in the formation and fast motion of a 3D null point along the arc located well above the plane of the sources. So, such a null point can quickly ignite a magnetic reconnection along the entire its trajectory. Pictorially, this can be presented as flipping the so-called two-dome magnetic-field structure (which is just the reason why such mechanism was called topological). The most important prerequisite for the development of topological instability in the two-dome structure is a cruciform arrangement of the magnetic sources in its base, and this condition is really satisfied in the case under consideration.Comment: LaTeX, rnaastex documentclass, 3 pages, 1 PDF figure, accepted for publication in the "Research Notes of the American Astronomical Society