I report on measurements of the properties of the top quark using data collected by the CDF and DØ detectors during Run II of the Fermilab Tevatron. The helicity of the W boson arising from top quark decay, the top quark decay branching ratios, and the top quark charge have all been measured, and the results in all cases are consistent with standard model expectations.

The semileptonic decay of a b-quark, b → clν, is considered in the relativistic limit where the decay products are approximately collinear. Analytic results for the double differential lepton energy distributions are given for finite charm-quark mass. Their use for the fast simulation of isolated lepton backgrounds from heavy quark decays is discussed.

A simple chiral quark model of the Nambu–Jona-Lasinio (NJL) type with a quark confinement mechanism is constructed for the description of the light meson sector of QCD at finite temperature. Unphysical quark production thresholds in the NJL model are excluded by an infrared cutoff in the momentum integration within quark loop diagrams. This chiral quark model satisfies the low energy theorems. ...

We consider the possibility of extracting the bottom quark mass from LEP data. The inclusive decay rate for Z → bb̄ + · · · is obtained at order αs by summing up the one-loop two-parton decay rate to the tree-level three-parton rate. We calculate the decay width of the Z-boson into two and three jets containing the b-quark including complete quark mass effects. In particular, we give analytic re...

We apply the method of perturbative fragmentation to study bottom fragmentation in top decay. We present the energy spectrum of b-quarks and b-flavoured hadrons in top decay. A reliable understanding of bottom-quark fragmentation in top-quark decay (t → bW) will be fundamental to accurately measure the top properties, such as its mass, at present and future high-energy colliders. At the LHC, fi...

We apply the method of perturbative fragmentation to study bottom fragmentation in top decay. We present the energy spectrum of b-quarks and b-flavoured hadrons in top decay. A reliable understanding of bottom-quark fragmentation in top-quark decay (t → bW) will be fundamental to accurately measure the top properties, such as its mass, at present and future high-energy colliders. At the LHC, fi...

We study the narrow decay width of low-lying penta-quark baryons in the QCD string theory in terms of gluonic excitations. In the QCD string theory, the penta-quark baryon decays via a gluonic-excited state of a baryon and meson system, where a pair of Y-shaped junction and anti-junction is created. Since lattice QCD shows that the lowest gluonicexcitation energy takes a large value of about 1 ...

We present the complete calculation of the top-quark decay width at next-to-next-to-leading order in QCD, including next-to-leading electroweak corrections as well as finite bottom quark mass and W boson width effects. In particular, we also show the first results of the fully differential decay rates for the top-quark semileptonic decay t → W(+)(l(+)ν)b at next-to-next-to-leading order in QCD....