Two-Loop Ultrasoft Running of the O(v^2) QCD Quark Potentials

The two-loop ultrasoft contributions to the next-to-leading logarithmic (NLL) running of the QCD potentials at order v^2 are determined. The results represent an important step towards the next-to-next-to-leading logarithmic (NNLL) description of heavy quark pair production and annihilation close to threshold.Comment: 13 pages, 3 figures; typos corrected, reference added, information on cross checks added on page 7; acknowledgments adde

Non-Relativistic Effective Field Theory for Perturbative Heavy Quark--Antiquark Systems

Recent developments for an effective theory for non-relativistic perturbative quark-antiquark systems are reviewed and some applications are discussed.Comment: 15 pages, latex (sprocl.sty), 2 postscript figures. Invited talk presented at the 5th Workshop on QCD (QCD 2000), Villefranche-sur-Mer, France, 3-7 Jan 200

Light Quark Mass Effects in Bottom Quark Mass Determinations

Recent results for charm quark mass effects in perturbative bottom quark mass determinations from $\Upsilon$ mesons are reviewed. The connection between the behavior of light quark mass corrections and the infrared sensitivity of some bottom quark mass definitions is examined in some detail.Comment: Invited talk presented at RADCOR-2000, Carmel, CA, Sep. 2000; 15 pages, latex, 3 postscript figures; eliminated typo in Eq.(3

Top Threshold Physics

Running a future Linear Collider at the top pair threshold allows for precise measurements of the mass, the widths and the couplings of the top quark. I give a nontechnical review on recent theoretical developments and the theory status in top threshold physics concerning QCD corrections and top quark finite lifetime and electroweak effects. I also discuss threshold physics in the context of measurements of the top Yukawa coupling from $e^+e^-\to t\bar t H$ and of squark pair production.Comment: 13 pages, 6 figures, PoS style. Invited talk presented at the International Workshop on Top Quark Physics, Coimbra, Portugal, 12-15 Jan 200

Charm Quark Mass from Inclusive Semileptonic B Decays

The MSbar charm quark mass is determined to be m_c(m_c)=1224+-17+-54 MeV from a global fit to inclusive B meson decay data, where the first error is experimental, and includes the uncertainty in alpha_s, and the second is an estimate of theoretical uncertainties in the computation. We discuss the implications of the pole mass renormalon in the determination of m_c.Comment: 7 pages, 2 tables; revtex4. References added, minor changes; version to appear in PL

Electroweak Absorptive Parts in NRQCD Matching Conditions

Electroweak corrections associated with the instability of the top quark to the next-to-next-to-leading logarithmic (NNLL) total top pair threshold cross section in e+e- annihilation are determined. Our method is based on absorptive parts in electroweak matching conditions of the NRQCD operators and the optical theorem. The corrections lead to ultraviolet phase space divergences that have to be renormalized and lead to NLL mixing effects. Numerically, the corrections can amount to several percent and are comparable to the known NNLL QCD corrections.Comment: 17 pages, revtex4, 4 postscript figures included; minor changes in text and references, title modified in printed versio

Three-Loop Anomalous Dimension of the Heavy Quark Pair Production Current in Non-Relativistic QCD

The three-loop non-mixing contributions to the anomalous dimension of the leading order quark pair production current in non-relativistic QCD are computed. It is demonstrated that the renormalization procedure can only be carried out consistently if the dynamics of both soft and the ultrasoft degrees of freedom is present for all scales below the heavy quark mass, and if the soft and ultrasoft renormalization scales are always correlated.Comment: 19 pages, revtex, 5 postscript figures include

Summing Logs of the Velocity in NRQCD and Top Threshold Physics

To achieve reliable predictions of the top-antitop threshold cross section at a future e+e- Linear Collider logarithms of the top velocity need to be resummed. I review the issues that make this problem complicated and show how the task can be achieved by renormalization in an effective theory using the so called velocity renormalization group. The most recent NNLL order results are discussed.Comment: 12 pages, uses ws-procs9x6.cls and rotating_pr.sty, 2 ps figures. Invited talk at Continuous Advances in QCD 2004, Minneapolis, USA, May 13-16,200