Size Of Power Corrections Research Articles

Comprehensive Bayesian analysis of rare (semi)leptonic and radiative [Formula: see text] decays.

The available data on |Delta B| = |Delta S| = 1 decays are in good agreement with the Standard Model when permitting subleading power corrections of about 15,% at large hadronic recoil. Constraining new-physics effects in mathcal {C}_{7}^{mathrm {}}, mathcal {C}_{9}^{mathrm {}}, mathcal {C}_{10}^{mathrm {}}, the data still demand the same size of power corrections as in the Standard Model. In the presence of chirality-flipped operators, all but one of the power corrections reduce substantially. The Bayes factors are in favor of the Standard Model. Using new lattice inputs for Brightarrow K^* form factors and under our minimal prior assumption for the power corrections, the favor shifts toward models with chirality-flipped operators. We use the data to further constrain the hadronic form factors in Brightarrow K and Brightarrow K^* transitions.

Revolution: Improving perturbative QCD

Perturbative QCD results in the MSbar scheme can be dramatically improved by switching to a scheme that accounts for the dominant power law dependence on the factorization scale in the operator product expansion. We introduce the ``MSR scheme'' which achieves this in a Lorentz and gauge invariant way. The MSR scheme has a very simple relation to MSbar, and can be easily used to reanalyze MSbar results. Results in MSR depend on a cutoff parameter R, in addition to the mu of MSbar. R variations can be used to independently estimate i) the size of power corrections, and ii) higher order perturbative corrections (much like mu in MSbar). We give two examples at three-loop order, the ratio of mass splittings in the B*-B and D*-D systems, and the Ellis-Jaffe sum rule as a function of momentum transfer Q in deep inelastic scattering. Comparing to data, the perturbative MSR results work well even for Q ~ 1 GeV, and the size of power corrections is reduced compared to those in MSbar.

Annihilation in charmless nonleptonic B decays

We show that the leading contributions to annihilation amplitudes in nonleptonic B → M 1 M 2 decays (where M 1 , 2 are charmless non-isosinglet mesons) of order α s ( m b ) Λ / m b are real and are determined by distribution functions that already occur in the lowest order factorization theorem [C.M. Arnesen, Z. Ligeti, I.Z. Rothstein and I.W. Stewart, hep-ph/0607001 ]. A complex nonperturbative parameter from annihilation first appears at O [ α s 2 ( Λ m b ) Λ / m b ] and real at lowest order. Thus, incalculable strong phases are suppressed in annihilation amplitudes, unless the α s ( Λ m b ) expansion breaks down. Modeling the distribution functions, we find that ( 11 ± 9 ) % and ( 15 ± 11 ) % of the absolute values of the measured B ¯ 0 → K − π + and B − → K − K 0 penguin amplitudes come from annihilation. This is consistent with the expected size of power corrections. LBNL–61096