Measurements of CP Violation, Mixing and Lifetimes of B Mesons with the BaBar Detector

We report the observation of CP violation in the $B^0$ meson system. Using a novel technique for time-dependent measurements, we measure a non-zero value for the CP-violating amplitude $\sin 2\beta$ at the 4.1 $\sigma$ level. We also report on precision measurements of the $B^+$ and $B^0$ lifetimes and the $B^0\bar{B}^0$ mixing frequency $\Delta m_d$ obtained with the same technique and on a first measurement of the time-dependent CP-violating amplitude in $B^0\to \pi^+\pi^-$ decays.Comment: 14 pages, 9 postscript figues, submitted to 9th International Symposium of Heavy Flavor Physic

Coherent photon bremsstrahlung and dynamics of heavy-ion collisions: comparison of different models

Differential spectra of coherent photon bremsstrahlung in relativistic heavy ion collisions are calculated within various schematic models of the projectile-target stopping. Two versions of the degradation length model, based on a phenomenological deceleration law, are considered. The simple shock wave model is studied analytically. The predictions of these models agree in the soft photon limit, where the spectrum is determined only by the final velocity distribution of charged particles. The results of these models in the case of central Au+Au collisions at various bombarding energies are compared with the predictions of the microscopic transport model UrQMD. It is shown that at the AGS energy the coherent photon bremsstrahlung exceeds the photon yield from $\pi^0$-decays at photon energies \omega\loo 50 MeV.Comment: 23 pages RevTeX, 9 eps Figure

Worst-case User Analysis in Poisson Voronoi Cells

In this letter, we focus on the performance of a worst-case mobile user (MU) in the downlink cellular network. We derive the coverage probability and the spectral efficiency of the worst-case MU using stochastic geometry. Through analytical and numerical results, we draw out interesting insights that the coverage probability and the spectral efficiency of the worst-case MU decrease down to 23% and 19% of those of a typical MU, respectively. By applying a coordinated scheduling (CS) scheme, we also investigate how much the performance of the worst-case MU is improved.Comment: Accepted, IEEE Communications Letter

MIMO Detection for High-Order QAM Based on a Gaussian Tree Approximation

This paper proposes a new detection algorithm for MIMO communication systems employing high order QAM constellations. The factor graph that corresponds to this problem is very loopy; in fact, it is a complete graph. Hence, a straightforward application of the Belief Propagation (BP) algorithm yields very poor results. Our algorithm is based on an optimal tree approximation of the Gaussian density of the unconstrained linear system. The finite-set constraint is then applied to obtain a loop-free discrete distribution. It is shown that even though the approximation is not directly applied to the exact discrete distribution, applying the BP algorithm to the loop-free factor graph outperforms current methods in terms of both performance and complexity. The improved performance of the proposed algorithm is demonstrated on the problem of MIMO detection