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

Phase transitions in exactly solvable decorated model of localized Ising spins and itinerant electrons

A hybrid lattice-statistical model of doubly decorated two-dimensional lattices, which have localized Ising spins at its nodal sites and itinerant electrons delocalized over decorating sites, is exactly solved with the help of a generalized decoration-iteration transformation. Under the assumption of a quarter filling of each couple of the decorating sites, the ground state constitutes either spontaneously long-range ordered ferromagnetic or ferrimagnetic phase in dependence on whether the ferromagnetic or antiferromagnetic interaction between the localized Ising spins and itinerant electrons is considered. The critical temperature of the spontaneously long-range ordered phases monotonically increases upon strengthening the ratio between the kinetic term and the Ising-type exchange interaction.Comment: 4 pages, 3 figures, presented at International Conference on Magnetism 2009 to be held on July 26-31 in Karlsruhe, Germany. submitted to J. Phys.: Conf. Se

Spin Polarisability of the Nucleon in the Heavy Baryon Effective Field Theory

We have constructed a heavy baryon effective field theory with photon as an external field in accordance with the symmetry requirements similar to the heavy quark effective field theory. By treating the heavy baryon and anti-baryon equally on the same footing in the effective field theory, we have calculated the spin polarisabilities $\gamma_i, i=1...4$ of the nucleon at third order and at fourth-order of the spin-dependent Compton scattering. At leading order (LO), our results agree with the corresponding results of the heavy baryon chiral perturbation theory, at the next-to-leading order(NLO) the results show a large correction to the ones in the heavy baryon chiral perturbation theory due to baryon-antibaryon coupling terms. The low energy theorem is satisfied both at LO and at NLO. The contributions arising from the heavy baryon-antibaryon vertex were found to be significant and the results of the polarisabilities obtained from our theory is much closer to the experimental data.Comment: 21pages, title changed, minimal correction

Semileptonic B Decays into Excited Charmed Mesons (D1D_1, D2∗D^*_2) in HQEFT

Exclusive semileptonic B decays into excited charmed mesons ($D_1$, $D^*_2$) are studied up to the order of $1/m_Q$ in the framework of the heavy quark effective field theory (HQEFT), which contains the contributions of both particles and antiparticles. Two wave functions $\eta^b_0$ and $\eta^c_0$, which characterize the contributions from the kinematic operator at the order of $1/m_Q$, are calculated by using QCD sum rule approach in HQEFT. Zero recoil values of other two wave functions $\kappa'_1$ and $\kappa'_2$ are extracted from the excited charmed-meson masses. Possible effects from the spin-dependent transition wave functions which arise from the magnetic operators at the order of $1/m_Q$ are analyzed. It is shown that the experimental measurements for the branching ratios of $B \to D_1 l\nu$ and $B \to D^*_2 l\nu$ can be understood in the framework of HQEFT.Comment: 27 pages, RevTex, 4 figures, 3 tables, to be published in IJMP

Techniques for Accurate Parallax Measurements for 6.7-GHz Methanol Masers

The BeSSeL Survey is mapping the spiral structure of the Milky Way by measuring trigonometric parallaxes of hundreds of maser sources associated with high-mass star formation. While parallax techniques for water masers at high frequency (22 GHz) have been well documented, recent observations of methanol masers at lower frequency (6.7 GHz) have revealed astrometric issues associated with signal propagation through the ionosphere that could significantly limit parallax accuracy. These problems displayed as a "parallax gradient" on the sky when measured against different background quasars. We present an analysis method in which we generate position data relative to an "artificial quasar" at the target maser position at each epoch. Fitting parallax to these data can significantly mitigate the problems and improve parallax accuracy

Combinatorial interpretation of Haldane-Wu fractional exclusion statistics

Assuming that the maximal allowed number of identical particles in state is an integer parameter, q, we derive the statistical weight and analyze the associated equation which defines the statistical distribution. The derived distribution covers Fermi-Dirac and Bose-Einstein ones in the particular cases q = 1 and q -> infinity (n_i/q -> 1), respectively. We show that the derived statistical weight provides a natural combinatorial interpretation of Haldane-Wu fractional exclusion statistics, and present exact solutions of the distribution equation.Comment: 8 pages, 2 eps-figure