QCD effective action with a most general homogeneous field background

We consider one-loop effective action of SU(3) QCD with a most general constant chromomagnetic (chromoelectric) background which has two independent Abelian field components. The effective potential with a pure magnetic background has a local minimum only when two Abelian components H_{\mu\nu}^3 and H_{\mu\nu}^8 of color magnetic field are orthogonal to each other. The non-trivial structure of the effective action has important implication in estimating quark-gluon production rate and p_T-distribution in quark-gluon plasma. In general the production rate depends on three independent Casimir invariants, in particular, it depends on the relative orientation between chromoelectric fields.Comment: 6 pages, 3 figures (9 pages in published version

Semi-Leptonic b-decay at Intermediate Recoil

We compute the O(\alpha_s^2) corrections to the differential rate of the semileptonic decay b -> clv at the "intermediate recoil" point, where the c-quark mass and the invariant mass of the leptons are equal. The calculation is based on an expansion around two opposite limits of the quark masses m_{b,c}: m_c ~ m_b and m_c << m_b. The former case was previously studied; we correct and extend that result. The latter case is new. The smooth matching of both expansions provides a check of both. We clarify the discrepancy between the recent determinations of the full NNLO QCD correction to the semileptonic b -> c rate, and its earlier estimate.Comment: 9 pages, 6 figures, Replaced figures, small format and typo corrections, added appendix and reference

Studying Human-Centered IT Innovation Using a Grounded Action Learning Approach

This paper describes how two research methodologies, grounded theory and action learning, were combined to produce a rigorous yet creative and flexible method for field study of a recent IT-based innovation, virtual teams. Essentially, an action learning program was used to train facilitators of virtual teams and generate research data while grounded theory techniques were used to analyze and interpret the data. This paper shows how this combined method can be used to develop local and practical theory for complex, human-centered areas of information technology. The implications of this grounded action learning approach for practice and research in IS will be discussed