Within the framework of a constituent quark model, we investigate heavy conserving weak decays ?c and ?b. This process involves elementary transitions us?du or s?udu¯ with as spectator, while for charmed baryon in initial state it can also occur via cs?dc to conserve flavor decays. It shows that symmetry (HQS) plays an essential role processes where acts spectator. For decays, dominance pole te...

In the framework of renormalon consideration, a role of the anomalous dependence of gluon propagator on the scale µ is shown for a large number of quark flavours as well as in the nonabelian theory, where the parameter of the " running " coupling constant evolution has a hidden dependence on the scale. A phenomenological matching between the modified renormalon and the static quark potential is...

It is about thirty years since the intense study of hot and dense nuclear matter in the form of Quark-Gluon Plasma (QGP) has started. A tremendous amount of effort has gone in for the development of four generations of experiments and a large number of data have been collected and analyzed. Major theoretical developments have been made at the fundamental level and theoretical models have been d...

The quark helicity measured in polarized deep inelastic scattering is different from the quark spin in the rest frame of the nucleon. We point out that the quark spin distributions ∆qRF (x) are connected with the quark helicity distributions ∆q(x) and the quark transversity distributions δq(x) by an approximate relation: ∆qRF (x) +∆q(x) = 2δq(x). This relation will be useful in order to measure...