Lifetimes of heavy hadrons beyond leading logarithms

The lifetime splitting between the B^+ and B_d^0 mesons has recently been calculated in the next-to-leading order of QCD. These corrections are necessary for a reliable theoretical prediction, in particular for the meaningful use of hadronic matrix elements computed with lattice QCD. Using results from quenched lattice QCD we find tau(B^+)/tau(B^0_d)=1.053 +/- 0.016 +/- 0.017, where the uncertainties from unquenching and 1/m_b corrections are not included. The lifetime difference of heavy baryons Xi_b^0 and \Xi_b^- is also discussed.Comment: 10 pages, 4 figures, Talk at Continuous Advances in QCD 2002/ ARKADYFEST,17-23 May 2002, Minneapolis, Minnesota, US

Supersymmetric corrections to Higgs decays and b-> s gamma for large tan beta

If tan beta is large, supersymmetric QCD corrections can become large, putting naive perturbation theory into doubt. I show how these tan-beta-enhanced corrections can be controlled to all orders in alpha_s tanbeta. The result is shown for the decays H^+ -> t b-bar and b -> s gamma.Comment: preprint no. added, typos corrected, talk at Moriond 200

BB−Bˉ\bar{B} mixing: decay matrix at high precision

I review the status of the Standard-Model prediction of the width difference $\Delta$$\Gamma$$_s$ among the two $B$$_s$ meson eigenstates. Ongoing effort addresses three-loop QCD corrections, corresponding to the next-to-next-to-leading order of QCD. With an improved theoretical precision of the ratio $\Delta$$\Gamma$$_s$/$\Delta$$M$$_s$, where $\Delta$$M$$_s$ denotes the mass difference in the $B$$_s$-$\bar{B}$s system, one can probe new physics in $\Delta$$M$$_s$ without sensitivity to |$V$$_{cb}$|, whose value is currently controversial

Next-to-Leading Order QCD Corrections to the Lifetime Difference of BsB_s Mesons

We compute the QCD corrections to the decay rate difference in the $B_s-\bar B_s$ system, $\Delta\Gamma_{B_s}$, in the next-to-leading logarithmic approximation using the heavy quark expansion approach. Going beyond leading order in QCD is essential to obtain a proper matching of the Wilson coefficients to the matrix elements of local operators from lattice gauge theory. The lifetime difference is reduced considerably at next-to-leading order. We find $(\Delta\Gamma/\Gamma)_{B_s}=(f_{B_s}/210 MeV)^2 [0.006 B(m_b)+0.150 B_S(m_b)-0.063]$ in terms of the bag parameters $B, B_S$ in the NDR scheme. As a further application of our analysis we also derive the next-to-leading order result for the mixing-induced CP asymmetry in inclusive $b\to u\bar ud$ decays, which measures $\sin 2\alpha$.Comment: 14 pages, LaTeX, 1 figure; minor modifications of the text, improved discussion of eq. (35), all results unchange

Towards next-to-next-to-leading-log accuracy for the width difference in the Bs−B¯s system: fermionic contributions to order (mc/mb)⁰ and (mc/mb)¹

We calculate a class of three-loop Feynman diagrams which contribute to the next-to-next-to-leading logarithmic approximation for the width difference ΔΓs in the B s −B ¯ s system. The considered diagrams contain a closed fermion loop in a gluon propagator and constitute the order αs2Nf, where Nf is the number of light quarks. Our results entail a considerable correction in that order, if ΔΓs is expressed in terms of the pole mass of the bottom quark. If the MS ¯ scheme is used instead, the correction is much smaller. As a result, we find a decrease of the scheme dependence. Our result also indicates that the usually quoted value of the NLO renormalization scale dependence underestimates the perturbative error

Laurent series expansion of a class of massive scalar one-loop integrals to ${\cal O}(\ep^2)

We use dimensional regularization to calculate the {\cal O}(\ep^2) expansion of all scalar one-loop one-, two-, three- and four-point integrals that are needed in the calculation of hadronic heavy quark production. The Laurent series up to {\cal O}(\ep^2) is needed as input to that part of the NNLO corrections to heavy flavor production at hadron colliders where the one-loop integrals appear in the loop-by-loop contributions. The four-point integrals are the most complicated. The {\cal O}(\ep^2) expansion of the three- and four-point integrals contains in general polylogarithms up to ${\rm Li}_4$ and functions related to multiple polylogarithms of maximal weight and depth four.Comment: 48 pages, 4 figures in the text, slight change in the title, one reference added, matches published versio

Matching conditions and Higgs mass upper bounds revisited

Matching conditions relate couplings to particle masses. We discuss the importance of one-loop matching conditions in Higgs and top-quark sector as well as the choice of the matching scale. We argue for matching scales $\mu_{0,t} \simeq m_t$ and $\mu_{0,H} \simeq max[ m_t, M_H ]$. Using these results, the two-loop Higgs mass upper bounds are reanalyzed. Previous results for $\Lambda\approx$ few TeV are found to be too stringent. For $\Lambda=10^{19}$ GeV we find $M_H < 180 \pm 4\pm 5$ GeV, the first error indicating the theoretical uncertainty, the second error reflecting the experimental uncertainty due to $m_t=175\pm6$ GeV.Comment: 20 pages, 6 figures; uses epsf and rotate macro