The effects of strong interactions on the two-loop electroweak radiative corrections to muon anomalous magnetic moment, ${a}_{\ensuremath{\mu}}{=(g}_{\ensuremath{\mu}}\ensuremath{-}2)/2,$ are examined. Short-distance logarithms shown be unaffected. computation long-distance contributions is improved by use an effective field theory approach that preserves chiral properties QCD and accounts for constraints from operator product expansion. Small, previously neglected, contributions, suppressed...

We discuss hadronic light-by-light scattering contribution to the muon anomalous magnetic moment a_\mu^{\rm lbl}, paying particular attention consistent matching between short- and long-distance behavior of amplitude. argue that short-distance QCD imposes strong constraints on this amplitude overlooked in previous analyses. find accounting for these leads approximately 50 per cent increase central value compared existing estimates. The becomes lbl}=136(25) \times 10^{-11}, thereby shifting...

We address the question whether a graviton could have small nonzero mass. The issue is subtle for two reasons: there discontinuity in mass lowest tree-level approximation, and, moreover, nonlinear four-dimensional theory of massive not defined unambiguously. First, we reiterate old argument that vanishing approximation breaks down since higher order corrections are singular However, exist nonperturbative solutions which correspond to summation terms and these continuous Furthermore, study...

We derive the lepton spectrum in semileptonic b decays from a nonperturbative treatment of QCD; it is based on an expansion 1/${\mathit{m}}_{\mathit{Q}}$ with ${\mathit{m}}_{\mathit{Q}}$ being heavy flavor quark mass. The leading corrections arising level are completely expressed terms difference mass hadron and quark. Nontrivial effects appear 1/${\mathit{m}}_{\mathit{Q}}^{2}$ affecting mainly end-point region; they different for meson baryon as well bottom charm decays.

Abstract We review the technique of calculation operator expansion coefficients. The main emphasis is put on gluon operators which appear in n ‐point functions induced by colourless quark currents. Two convenient schemes are discussed detail: abstract method and based Fock‐Schwinger gauge for vacuum field. consider a large number instructive examples important from point view physical applications.

The key quantity of the heavy quark theory is mass $m_Q$. Since quarks are unobservable one can suggest different definitions One most popular choices pole routinely used in perturbative calculations and some analyses based on expansions. We show that no precise definition be given full once non-perturbative effects included. Any this suffers from an intrinsic uncertainty order $\Lam /m_Q$. This fact succinctly described by existence infrared renormalon generating a factorial divergence...

A generalization of the operator product expansion is used to find differential distributions in inclusive semileptonic weak decays heavy flavors QCD. In particular, double distribution electron energy and invariant mass lepton pair calculated. We are able calculate an essentially model-independent way as a series ${m}_{Q}^{\ensuremath{-}1}$ where ${m}_{Q}$ quark mass. All effects up ${m}_{Q}^{\ensuremath{-}2}$ included.

An attempt is made to present an instanton calculus in a relatively simple form. The physical meaning of instantons explained by the example quantum-mechanical problem energy levels two-humped potential. nonstandard solution this based on analyzed, and reader acquainted with main technical elements used approach. Instantons quantum chromodynamics are then considered. Euclidean formulation theory described. Classical solutions field equations (the Belavin–Polyakov–Shvarts–Tyapkin instantons)...

We present a self-consistent method for treating nonperturbative effects in inclusive nonleptonic and semileptonic decays of heavy flavour hadrons. These give rise to powerlike corrections ∝ 1mQn with n ⩾ 2. The leading correction the branching ratio occurs = It is expressed terms vector-pseudoscalar mass splitting: δBRslBRsl≅BRnl·6 [(Mv2−Mp2)mQ2](c+2−c−2)2Nc yields reduction BRsl. This contributes width sign opposite that perturbative are non-leading 1Nc. In beauty former reduces latter by...