Abstract:
Thermodynamics of a heavy quark-antiquark pair in SU(3)-QCD is studied below the deconfinement critical temperature, $T_c$. In the quenched case, a model of the string passing through heavy valence gluons yields a correct estimate of $T_c$ and a behavior of the string tension near $T_c$. For two light flavors, entropy and internal energy can be obtained from the partition function of heavy-light mesons and baryons. They are in a good qualitative agreement with the lattice results.

Abstract:
We describe the analytic calculation of the fermionic two-loop QCD corrections to the heavy-quark pair production process in the quark-antiquark channel.

Abstract:
Thermodynamics of a heavy quark-antiquark pair in SU(3)-QCD is studied both below and above the deconfinement critical temperature $T_c$. In the quenched case, a model of the string passing through heavy valence gluons yields a correct estimate of $T_c$ and the critical behavior of the string tension below $T_c$. For two light flavors, entropy and internal energy below $T_c$ can be obtained from the partition function of heavy-light mesons and baryons. To calculate the free energy of the system above $T_c$, we apply second-order perturbation theory in the interaction of the quark-gluon plasma constituents with the static quark-antiquark pair. The results for the entropy and internal energy, obtained both below and above $T_c$, are compared with recent lattice data.

Abstract:
The colour fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(3) lattice QCD, in a $24^3\times 48$ lattice at $\beta=6.2$ and $a=0.07261(85)\,fm$. We study two geometries, one with a U shape and another with an L shape. The particular cases of the two gluon glueball and quark-antiquark are also studied, and the Casimir scaling is investigated in a microscopic perspective. This also contributes to understand confinement with flux tubes and to discriminate between the models of fundamental versus adjoint confining strings, analogous to type-II and type-I superconductivity.

Abstract:
We model the spectral effect of open flavor meson-meson thresholds in heavy quarkonia. The proposed energy dependent quark-antiquark static potential tries to incorporate in a quark model scheme the results from unquenched lattice calculations. A good qualitative and a reasonable quantitative description of charmonium and bottomonium, including the "new charmonium-like" states, is obtained.

Abstract:
A new formula for the heavy quark-antiquark spin dependent potential is given by using the techniques developed in the heavy quark effective theory. The leading logarithmic quark mass terms emerging from the loop contributions are explicitly extracted and summed up. There is no renormalization scale ambiguity in this new formula. The spin-dependent potential in the new formula is expressed in terms of three independent color-electric and color-magnetic field correlation functions, and it includes both the Eichten-Feinberg's formula and the one-loop QCD result as special cases.

Abstract:
The chromoelectric and chromomagnetic fields, created by a static gluon-quark-antiquark system, are computed in the quenched approximation of lattice QCD, in a $24^3\times 48$ lattice at $\beta=6.2$. We study two geometries, one with a U shape and another with an L shape. The degenerate case of the two gluon glueball is also studied. This is relevant to understand the microscopic structure of hadrons, in particular of hybrids. This also contributes to understand confinement with flux tubes of the chromoelectric field, and to discriminate between the models of fundamental or adjoint tubes.

Abstract:
The grand canonical potential for a static quark-antiquark pair at non-vanishing chemical potential was determined at several temperatures. The dynamical staggered simulations were carried out with 2+1 physical quarks along the Lines of Constant Physiscs (LCP).

Abstract:
We study the singlet part of the free energy of a static quark anti-quark pair at finite temperature in three flavor QCD with degenerate quark masses using $N_{\tau}=4$ and 6 lattices with Asqtad staggered fermion action. We look at thermodynamics of the system around phase transition and study its scaling with lattice spacing and quark masses.

Abstract:
In this paper we introduce a new approach to identify a bottom quark-antiquark pair inside a single jet with high transverse momentum by using the jet substructure in the center-of-mass frame of the jet. We demonstrate that the method can be used to discriminate the boosted heavy particles decaying to a $b\bar{b}$ final state from QCD jets. Applications to searches for the standard model Higgs boson ($H$) decaying to $b\bar{b}$ when produced in association with a weak vector boson are also discussed.