Quark model predictions for the electron energy spectrum in seileptonic D and B decays

The constituent quark model is used to predict the electron energy spectrum in semileptonic D and B meson decays. Particular attention is paid to the endpoint region of the electron spectrum in B decays since this is crucial to a determination of the b --> u weak mixing angle

Quark model predictions for the electron energy spectrum in seileptonic D and B decays

The constituent quark model is used to predict the electron energy spectrum in semileptonic D and B meson decays. Particular attention is paid to the endpoint region of the electron spectrum in B decays since this is crucial to a determination of the b --> u weak mixing angle

Semileptonic B and Lambda_b Decays and Local Duality in QCD

The inclusive and exclusive semileptonic decay distributions for b -> c decay are computed in the Shifman-Voloshin limit. The inclusive decay distributions (computed using an operator product expansion) depend on quark masses, and the exclusive decay distributions depend on hadron masses. Nevertheless, we show explicitly how the first two terms in the 1/m expansion match between the inclusive and exclusive decays. Agreement between the inclusive and exclusive decay rates requires a minimum smearing region of size Lambda_QCD before local duality holds in QCD. The alpha_s corrections to the inclusive and exclusive decay rates are also shown to agree to order (log m)/m^2. The alpha_s/m^2 corrections are used to obtain the alpha_s correction to Bjorken's inequality on the slope of the Isgur-Wise function.Comment: 22 pages, 3 eps figures, uses revtex (Revision: a discussion of radiative corrections to the bound K>0 of Section 7.B has been added; some typos, including labels in fig 2

Perturbative corrections to zero recoil inclusive BB decay sum rules

Comparing the result of inserting a complete set of physical states in a time ordered product of $b$ decay currents with the operator product expansion gives a class of zero recoil sum rules. They sum over physical states with excitation energies less than $\Delta$, where $\Delta$ is much greater than the QCD scale and much less than the heavy charm and bottom quark masses. These sum rules have been used to derive an upper bound on the zero recoil limit of the $B\to D^*$ form-factor, and on the matrix element of the kinetic energy operator between $B$ meson states. Perturbative corrections to the sum rules of order $\alpha_s(\Delta) \Delta^2/m_{c,b}^2$ have previously been computed. We calculate the corrections of order $\alpha_s(\Delta)$ and $\alpha_s^2(\Delta) \beta_0$ keeping all orders in $\Delta/m_{c,b}$, and show that these perturbative QCD corrections suppressed by powers of $\Delta/m_{c,b}$ significantly weaken the upper bound on the zero recoil $B\to D^*$ form-factor, and also on the kinetic energy operator's matrix element.Comment: 13 pages revtex, four figures included; minor change

Semileptonic B and D decays in the quark model

We predict the matrix elements and resulting electron spectra for semileptonic meson decays using the quark potential model. Particular attention is paid to the high-energy electron end-point region in B decay since it is crucial to a determination of the b→u weak mixing angle. It is argued that in this region the usual inclusive ("quark decay") calculations are unjustified and must be replaced by explicit sums over decays of the original meson into low-mass exclusive hadronic final states

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The neutron and its role in cosmology and particle physics

Experiments with cold and ultracold neutrons have reached a level of precision such that problems far beyond the scale of the present Standard Model of particle physics become accessible to experimental investigation. Due to the close links between particle physics and cosmology, these studies also permit a deep look into the very first instances of our universe. First addressed in this article, both in theory and experiment, is the problem of baryogenesis ... The question how baryogenesis could have happened is open to experimental tests, and it turns out that this problem can be curbed by the very stringent limits on an electric dipole moment of the neutron, a quantity that also has deep implications for particle physics. Then we discuss the recent spectacular observation of neutron quantization in the earth's gravitational field and of resonance transitions between such gravitational energy states. These measurements, together with new evaluations of neutron scattering data, set new constraints on deviations from Newton's gravitational law at the picometer scale. Such deviations are predicted in modern theories with extra-dimensions that propose unification of the Planck scale with the scale of the Standard Model ... Another main topic is the weak-interaction parameters in various fields of physics and astrophysics that must all be derived from measured neutron decay data. Up to now, about 10 different neutron decay observables have been measured, much more than needed in the electroweak Standard Model. This allows various precise tests for new physics beyond the Standard Model, competing with or surpassing similar tests at high-energy. The review ends with a discussion of neutron and nuclear data required in the synthesis of the elements during the "first three minutes" and later on in stellar nucleosynthesis.Comment: 91 pages, 30 figures, accepted by Reviews of Modern Physic