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

Major loop reconstruction from switching of individual particles

Major hysteresis loops of groups of isolated 60 mm square garnet particles of a regular two-dimensional array, have been measured magnetooptically. Individual loops for each particle were measured, and the statistics of the distribution of coercivities and interaction fields was determined. It is shown that from the measured coercivity distribution and calculated magnetostatic interaction fields the major hysteresis loop can be reconstructed. The switching sequence, and the major loop of an assembly of 535 particles were calculated numerically for two cases: first, when calculating the magnetostatic interaction, the 25 particles were assumed to be isolated; second, the major loop of the same 25 particles, embedded into a 939 square, was reconstructed taking into account the interactions among all 81 particles. The numerically simulated major hysteresis loops agree very well with the measured loops, demonstrating the reliability of numerical modeling

Electron-Positron Annihilation into Hadron-Antihadron Pairs

The reactions of electron-positron to nucleon-antinucleon pairs are studied in a non-perturbative quark model. The work suggests that the two-step process, in which the primary quark-antiquark pair forms first a vector meson which in turn decays into a hadron pair, is dominant over the one-step process in which the primary quark-antiquark pair is directly dressed by additional quark-antiquark pairs to form a hadron pair. To reproduce the experimental data of the reactions of electron-positron to proton-antiproton and electron-positron to neutron-antineutron a D-wave omega-like vector meson with a mass of around 2 GeV has to be introduced.Comment: 15 pages, 6 figure

Bayesian stochastic blockmodeling

This chapter provides a self-contained introduction to the use of Bayesian inference to extract large-scale modular structures from network data, based on the stochastic blockmodel (SBM), as well as its degree-corrected and overlapping generalizations. We focus on nonparametric formulations that allow their inference in a manner that prevents overfitting, and enables model selection. We discuss aspects of the choice of priors, in particular how to avoid underfitting via increased Bayesian hierarchies, and we contrast the task of sampling network partitions from the posterior distribution with finding the single point estimate that maximizes it, while describing efficient algorithms to perform either one. We also show how inferring the SBM can be used to predict missing and spurious links, and shed light on the fundamental limitations of the detectability of modular structures in networks.Comment: 44 pages, 16 figures. Code is freely available as part of graph-tool at https://graph-tool.skewed.de . See also the HOWTO at https://graph-tool.skewed.de/static/doc/demos/inference/inference.htm

Pump induced Autler-Townes effect and A-T mixing in a four level atoms

It is shown by theoretical simulation that tuning of the pump power can induce mixing and crossing of Autler-Townes(A-T)components of closely spaced transitions in atoms. Pump radiation also leads to small shifts of the central hole of A-T doublet. Off-resonance pumping gives an asymmetry in the A-T components and by controlling pump frequency detuning it is also possible to mix the A-T components.Comment: 10 Pages, 3 figur

Runaway evaporation for optically dressed atoms

Forced evaporative cooling in a far-off-resonance optical dipole trap is proved to be an efficient method to produce fermionic- or bosonic-degenerated gases. However in most of the experiences, the reduction of the potential height occurs with a diminution of the collision elastic rate. Taking advantage of a long-living excited state, like in two-electron atoms, I propose a new scheme, based on an optical knife, where the forced evaporation can be driven independently of the trap confinement. In this context, the runaway regime might be achieved leading to a substantial improvement of the cooling efficiency. The comparison with the different methods for forced evaporation is discussed in the presence or not of three-body recombination losses

The magnetic dipole transitions in the (cbˉ)(c\bar{b}) binding system

The magnetic dipole transitions between the vector mesons $B_c^*$ and their relevant pseudoscalar mesons $B_c$ ($B_c$, $B_c^*$, $B_c(2S)$, $B_c^*(2S)$, $B_c(3S)$ and $B_c^*(3S)$ etc, the binding states of $(c\bar{b})$ system) of the $B_c$ family are interesting. To see the `hyperfine' splitting due to spin-spin interaction is an important topic for understanding the spin-spin interaction and the spectrum of the the $(c\bar{b})$ binding system. The knowledge about the magnetic dipole transitions is also very useful for identifying the vector boson $B_c^*$ mesons experimentally, whose masses are just slightly above the masses of their relevant pseudoscalar mesons $B_c$ accordingly. Considering the possibility to observe the vector mesons via the transitions at $Z^0$ factory and the potentially usages of the theoretical estimate on the transitions, we fucus our efforts on calculating the magnetic dipole transitions, i.e. precisely to calculate the rates for the transitions such as decays $B_c^*\to B_c\gamma$ and $B_c^*\to B_c e^+e^-$, and particularly work in the Behte-Salpeter framework. In the estimate, as a typical example, we carefully investigate the dependance of the rate $\Gamma(B_c^*\to B_c\gamma)$ on the mass difference $\Delta M=M_{B_c^*}-M_{B_c}$ as well.Comment: 10 pages, 2 figures, 1 tabl