Y. Kiyo

Next-to-Next-to-Next-to-Leading Order QCD Prediction for the Top Antitop S-Wave Pair Production Cross Section Near Threshold in e + e − Annihilation

We present the third-order QCD prediction for the production of top antitop quark pairs in electron-positron collisions close to the threshold in the dominant S-wave state. We observe a significant reduction of the theoretical uncertainty and discuss the sensitivity to the top quark mass and width.

Leptonic decay of the

We present the complete next-to-next-to-next-to-leading order short-distance and bound-state QCD correction to the leptonic decay rate Γ(ϒ(1S)→ℓ+ℓ-) of the lowest-lying spin-1 bottomonium state. The perturbative QCD prediction is compared to the measurement Γ(ϒ(1S)→e+e-)=1.340(18)  keV.

\Upsilon

We present new results on the NNNLO top-antitop production cross section near threshold from potential and ultrasoft gluon corrections. The new non-logarithmic third-order terms are in the 10% range and lead to a significant reduction in the theoretical error.

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Abstract We compute the energy levels of some of the lower-lying heavy quarkonium states perturbatively up to O ( α s 5 m ) and O ( α s 5 m log α s ) . Stability of the predictions depends crucially on the unknown 4-loop pole- MS ¯ mass relation. We discuss the current status of the predictions with respect to the observed bottomonium spectrum.

S

We report on the feasibility of the direct measurement of the top Yukawa coupling g_t at the International Linear Collider (ILC) during its first phase of operation with a center-of-mass energy of 500 GeV. The signal and background models incorporate the non-relativistic QCD corrections which enhance the production cross section near the t-tbar threshold. The e+e- -> t tbar H signal is reconstructed in the 6-jet + lepton and the 8-jet modes. The results from the two channels are combined. The background processes considered are e+e- -> t bbar W- / tbar b W+ (which includes e+e- -> t tbar), e+e- -> t tbar Z, and e+e- -> t tbar g* -> t tbar b bar. We use a realistic fast Monte-Carlo detector simulation. Signal events are selected using event shape variables, through jet clustering, and by identifying heavy flavor jets. Assuming a Higgs mass of 120 GeV, polarized electron and positron beams with (Pe-,Pe+) = (-0.8,+0.3), and an integrated luminosity of 1 ab-1, we estimate that the e+e- -> t tbar H events can be seen with a statistical significance of 5.2 sigma, corresponding to the relative top Yukawa coupling measurement accuracy of |Delta g_t / g_t| = 10%.

) meson at third order in QCD

Abstract We derive a full formula for the energy level of a heavy quarkonium state identified by the quantum numbers n , l , s and j , up to O ( α s 5 m ) and O ( α s 5 m log ⁡ α s ) in perturbative QCD. The QCD Bethe logarithm is given in a one-parameter integral form. The rest of the formula is given as a combination of rational numbers, transcendental numbers ( π , ζ ( 3 ) , ζ ( 5 ) ) and finite sums (besides the 3-loop constant a ¯ 3 of the static potential whose full analytic form is still unknown). A derivation of the formula is given.

NNNLO results on top-quark pair production near threshold

A bstractCombining recent perturbative analyses on the static QCD potential and the quark pole mass, we find that, for the heavy quarkonium states cc¯

Measuring the top Yukawa coupling at the ILC at

c\overline{c}