S. Yazaki

QCD sum rules for heavy quark systems

Abstract In this paper we present in a detailed and coherent fashion our work on QCD sum rules for equal mass heavy quark meson states. We discuss the technical procedures used to calculate the perturbative and non-perturbative contributions to the vacuum polarization, which have been calculated for all currents up to and including spin 2++. Using dispersion relations, sum rules are derived. Extensive applications are made to the lowest lying states of the charmonium and upsilon systems. The masses of the S- and P-wave charmonium levels are reproduced to a high degree of accuracy, and the mass of the 1P1 level is predicted at 3.51 GeV. For the upsilon system it only appears to be possible to predict the γ-ηb splitting which gives 60 MeV. Very accurate values are given for the current quark masses at p2 = −mq2: mc = 1.28 GeV and mb = 4.25 GeV.

L = 1 light quark mesons in QCD

Abstract Using the Borel transformed QCD sum rule formalism, the masses of L = 1 light quark mesons with isospin I = 1 and I = 0 are calculated. Non-perturbative effects from higher dimensional operators up to dimension d = 6 in the operator product expansion are taken into account.

Hadron Couplings to Goldstone Bosons in {QCD}

Abstract We calculate coupling constants in QCD by extrapolating from the asymptotic freedom regime using QCD sum rules. The novel feature is that these amplitudes are dominated by the quark condensate when one leg is a pseudoscalar Goldstone boson. We find many couplings and in particular the remarkable formulas g π NN 2 /4π≌2 5 π 3 ⨍ π 2 /M N 2 and g ωρπ = (2⨍ ρ /m ρ )(e/2√2) .

Masses and Couplings of Open Beauty States in {QCD}

Abstract Masses and couplings of open beauty states (strange and non-strange) with J pC - 0 ++ , 0 −+ , 1 −− , and 1++ are calculated using the QCD sum rule formalism. Non-perturbative effects due to quark and gluon condensate operators are shown to be important, confirming earlier calculations for equal quark mass systems.

QCD contribution to vacuum polarization: The pseudoscalar unequal mass case

Abstract We have computed to first order in α s the perturbative and non-perturbative contributions to the vacuum polarization from the pseudoscalar current in the unequal mass case.

Two-point functions for flavour changing currents in QCD

Abstract We complete the calculations of two-point functions in QCD by presenting the results for the flavour changing vector current, including perturbative and non-perturbative contributions (to first order in αs).

A QCD sum rule calculation of the K0 − K0 mixing parameter B

Abstract We present a QCD sum rule calculation of the K 0 − K 0 mixing parameter B , employing pseudoscalar currents for the currents coupling to the K-meson in the three-point function related to B . Our calculation shows that there is a large cancellation between factorizable and non-factorizable terms of order 1/ N . The result for the parameter B is B = 0.84 ± 0.08. In addition we obtain an excellent sum rule for the K-meson parameters.

QCD contributions to vacuum polarization

Abstract We have computed to lowest non-trivial order the perturbative and non-perturbative contributions to the vacuum polarization from all currents up to and including spin 2++. These expressions are important, for example to evaluate QCD sum rules for heavy and light quark systems as shown by Shifman, Vainshtein and Zakharov. Most of the known ones are verified, one slightly changed, and many new ones are displayed.

Nonleptonic decays of kaons in the 1Nc expansion

Abstract The 1 N c expansion is shown to give a systematic way to calculate hadronic matrix elements of weak currents by classifying quark gluon diagrams in terms of topology. The leading term of the 1 N c expansion is found to be color-disconnected. The empirical rule for the magnitude of the ΔI = 3 2 part of the K → ππ decay is justified in the leading-order approximation. Soft pion theorems are shown to be satisfied in the leading order.

Baryons in QCD and chiral symmetry breaking parameters

Abstract We calculate all baryons in the 56 representation using QCD sum rules. All masses are well predicted and require stringent values of the chiral parameters 〈0|ūu|〉 = −(230 ± 15MeV)3andγ = 〈s¯s〉/〈ūu〉 − 1 = −0.19 ± 0.02. The determination of γ is the most precise to date, the strange quark mass and the quark condensate are also accurately fixed.