A More Precise Extraction of |V_{cb}| in HQEFT of QCD

The more precise extraction for the CKM matrix element |V_{cb}| in the heavy quark effective field theory (HQEFT) of QCD is studied from both exclusive and inclusive semileptonic B decays. The values of relevant nonperturbative parameters up to order 1/m^2_Q are estimated consistently in HQEFT of QCD. Using the most recent experimental data for B decay rates, |V_{cb}| is updated to be |V_{cb}| = 0.0395 \pm 0.0011_{exp} \pm 0.0019_{th} from B\to D^{\ast} l \nu decay and |V_{cb}| = 0.0434 \pm 0.0041_{exp} \pm 0.0020_{th} from B\to D l \nu decay as well as |V_{cb}| = 0.0394 \pm 0.0010_{exp} \pm 0.0014_{th} from inclusive B\to X_c l \nu decay.Comment: 7 pages, revtex, 4 figure

Mathematical modelling and experimental validation of electrostatic sensors for rotational speed measurement

Recent research has demonstrated that electrostatic sensors can be applied to the measurement of rotational speed with excellent repeatability and accuracy under a range of conditions. However, the sensing mechanism and fundamental characteristics of the electrostatic sensors are still largely unknown and hence the design of the sensors is not optimised for rotational speed measurement. This paper presents the mathematical modelling of strip electrostatic sensors for rotational speed measurement and associated experimental studies for the validation of the modelling results. In the modelling, an ideal point charge on the surface of the rotating object is regarded as an impulse input to the sensing system. The fundamental characteristics of the sensor, including spatial sensitivity, spatial filtering length and signal bandwidth, are quantified from the developed model. The effects of the geometric dimensions of the electrode, the distance between the electrode and the rotor surface and the rotational speed being measured on the performance of the sensor are analyzed. A close agreement between the modelling results and experimental measurements has been observed under a range of conditions. Optimal design of the electrostatic sensor for a given rotor size is suggested and discussed in accordance with the modelling and experimental results

Lifetime Difference and Endpoint effect in the Inclusive Bottom Hadron Decays

The lifetime differences of bottom hadrons are known to be properly explained within the framework of heavy quark effective field theory(HQEFT) of QCD via the inverse expansion of the dressed heavy quark mass. In general, the spectrum around the endpoint region is not well behaved due to the invalidity of $1/m_Q$ expansion near the endpoint. The curve fitting method is adopted to treat the endpoint behavior. It turns out that the endpoint effects are truly small and the explanation on the lifetime differences in the HQEFT of QCD is then well justified. The inclusion of the endpoint effects makes the prediction on the lifetime differences and the extraction on the CKM matrix element $|V_{cb}|$ more reliable.Comment: 11 pages, Revtex, 10 figures, 6 tables, published versio

|V_ub| and |V_cb|, Charm Counting and Lifetime Differences in Inclusive Bottom Hadron Decays

Inclusive bottom hadron decays are analyzed based on the heavy quark effective field theory (HQEFT). Special attentions in this paper are paid to the b\to u transitions and nonspectator effects. As a consequence, the CKM quark mixing matrix elements |V_ub| and |V_cb| are reliably extracted from the inclusive semileptonic decays B\to X_u e \nu and B\to X_c e \nu. Various observables, such as the semileptonic branch ratio B_SL, the lifetime differences among B^-, B^0, B_s and \Lambda_b hadrons, the charm counting n_c, are predicted and found to be consistent with the present experimental data.Comment: 20 pages, Revtex, 4 figures and 2 table

Weak coupling d-wave BCS superconductivity and unpaired electrons in overdoped La_{2-x}Sr_{x}CuO_{4} single crystals

The low-temperature specific heat (SH) of overdoped La_{2-x}Sr_{x}CuO_{4} single crystals (0.178=<x=<0.290) has been measured. For the superconducting samples (0.178=<x=<0.238), the derived gap values (without any adjusting parameters) approach closely onto the theoretical prediction \Delta_{0}=2.14k_{B}T_{c} for the weak-coupling d-wave BCS superconductivity. In addition, the residual term \gamma(0) of SH at H=0 increases with x dramatically when beyond x~0.22, and finally evolves into the value of a complete normal metallic state at higher doping levels, indicating growing amount of unpaired electrons. We argue that this large \gamma(0) cannot be simply attributed to the pair breaking induced by the impurity scattering, instead the phase separation is possible.Comment: 6 pages, 6 figures; Contents added; Accepted for publication in Phys. Rev.