The Physics of the B Factories

This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C

ELECTRODYNAMICS OF AN ION INVERTED V

Particle precipitation around the earth's polar regions may be the footprint of various energizing phenomena in the magnetosphere. Satellite-observed electron fluxes whose peak energy increases then decreases are called inverted V's. The Atmosphere Explorer-D Low Energy Electron (LEE) data for January 11, 1976 indicates that the precipitating ions have been accelerated. In this event the spectrograms of the ion flux shows the change of the peak energy with time characteristic of an inverted V. The electron population is decelerated as the ion population is accelerated, consistent with a downward electric field. The Birkeland current at an inverted V may be calculated in two ways: from the divergence of the electric field or from the observed particle fluxes. We found that the two methods agree on the location of Birkeland current throughout the event, but the magnitudes are not the same. This is not surprising, since the component of (DEL)((')(SIGMA)(.)(')E) perpendicular to the trajectory can not be determined. The electric potential along the spacecraft's trajectory (790-650 km altitude) was calculated from the measured electric fields. The sum of the parallel potential drop (inferred from the ion distribution function) and the ionospheric potential gives the potential profile at the magnetosphere. The parallel electric field thus partially decoupled the ionospheric flow from the magnetospheric flow. The electric field pattern in the magnetosphere-ionosphere system demands field-aligned currents. When the thermal current is insufficient, a field-aligned potential drop can accelerate particles to satisfy the requirements. The thermal electron current from the ionosphere is much greater than that from the magnetosphere. Thus, it is more common to observe the signatures of an upward electric field: the electron "inverted V". In the ion inverted V observed during AE-D orbit 1141, the postulated parallel potential has reduced the required parallel current. This high potential had to develop because the required amount of downward current would have quickly evacuated the ionospheric electrons available to supply the original requirement of a downward current

The BaBar detector: Upgrades, operation and performance

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The BaBar detector

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Measurement of the branching fraction and CP violating asymmetries in neutral B decays to D*+- D-+

We present measurements of the branching fraction and CP-violating asymmetries for neutral B decays to D*+-D-+. The measurement uses a data sample of approximately 88 million Y(4S) --> B Bbar decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. We measure the branching fraction to be (8.8 +- 1.0 +- 1.3) x 10^-4 and the time-integrated CP-violating asymmetry between the rates to D*+D- and D*-D+ to be A = -0.03 +- 0.11 +- 0.05. We also measure the time-dependent CP-violating asymmetry parameters to be S-+ = -0.24 +- 0.69 +- 0.12, C-+ = -0.22 +- 0.37 +- 0.10 for B --> D*-D+ and S+- = -0.82 +- 0.75 +- 0.14$, C+- = -0.47 +- 0.40 +- 0.12 for B --> D*+D-. In each case the first error is statistical and the second error is systematic.Comment: 7 pages, 3 figures, published as Phys. Rev. Lett 90 (2003) 22180

Measurement of B0 ---> D(*)+ D*- branching fractions and B0 ---> D*+(s) D*- polarization with a partial reconstruction technique

We present a study of the decays B0->D_s(*)+D*-, using 20.8 fb-1 of e+e- annihilation data recorded with the BABAR detector. The analysis is conducted with a partial reconstruction technique, in which only the D_s(*)+ and the soft pion from the D*- decay are reconstructed. We measure the branching fractions BR(B0->D_s+D*-) = (1.03 +/- 0.14 +/- 0.13 +/- 0.26)% and BR(B0->D_s*+D*-) = (1.97 +/- 0.15 +/- 0.30 +/- 0.49)%, where the first error is statistical, the second is systematic, and the third is the error due to the D_s+->phi pi+ branching fraction uncertainty. From the B0->D_s*+D*- angular distributions, we measure the fraction of longitudinal polarization Gamma_L/Gamma = (51.9 +/- 5.0 +/- 2.8)%, which is consistent with theoretical predictions based on factorization.Comment: 9 pages, 4 postscript figues, submitted to Physical Review D (Rapid Communications

Measurement of the CKM matrix element |V(ub)| with B ---> rho e nu decays

We present a measurement of the branching fraction for the rare decays B->rho e nu and extract a value for the magnitude of Vub, one of the smallest elements of the Cabibbo-Kobayashi-Maskawa quark-mixing matrix. The results are given for five different calculations of form factors used to parametrize the hadronic current in semileptonic decays. Using a sample of 55 million BBbar meson pairs recorded with the BABAR detector at the PEP-II e+e- storage ring, we obtain Br(B0->rho- e+ nu)=(3.29 +-0.42 +-0.47 +-0.60) x 10^-4 and |Vub|=(3.64 +-0.22 +-0.25 +0.39-0.56)x10^-3, where the uncertainties are statistical, systematic, and theoretical, respectively.Comment: Submitted to Phys. Rev. Let