In supersymmetric grand-unified models, the lepton mixing matrix can possibly affect flavor-changing transitions in the quark sector. We present a detailed analysis of a model proposed by Chang, Masiero and Murayama, in which the near-maximal atmospheric neutrino mixing angle governs large new b -> s transitions. Relating the supersymmetric low-energy parameters to seven new parameters of this SO(10) GUT model, we perform a correlated study of several flavor-changing neutral current (FCNC) processes. We find the current bound on B(tau -> mu gamma) more constraining than B(B -> X_s gamma). The LEP limit on the lightest Higgs boson mass implies an important lower bound on tan beta, which in turn limits the size of the new FCNC transitions. Remarkably, the combined analysis does not rule out large effects in B_s-B_s-bar mixing and we can easily accomodate the large CP phase in the B_s-B_s-bar system which has recently been inferred from a global analysis of CDF and DO data. The model predicts a particle spectrum which is different from the popular Constrained Minimal Supersymmetric Standard Model (CMSSM). B(tau -> mu gamma) enforces heavy masses, typically above 1 TeV, for the sfermions of the degenerate first two generations. However, the ratio of the third-generation and first-generation sfermion masses is smaller than in the CMSSM and a (dominantly right-handed) stop with mass below 500 GeV is possible.

We present an algorithm that reveals relevant contributions in non-threshold-type asymptotic expansion of Feynman integrals about a small parameter. It is shown that the problem reduces to finding a convex hull of a set of points in a multidimensional vector space.

We calculate the two-loop matching corrections for the gauge couplings at the Grand Unification scale in a general framework that aims at making as few assumptions on the underlying Grand Unified Theory (GUT) as possible. In this paper we present an intermediate result that is general enough to be applied to the Georgi-Glashow $SU(5)$ as a ``toy model“. The numerical effects in this theory are found to be larger than the current experimental uncertainty on $\alpha_s$. Furthermore, we give many details of the calculation regarding renormalization procedure, tadpole terms, gauge fixing and the treatment of group theory factors, which is useful preparational work for the extension of the calculation to supersymmetric GUTs.

s</sub>³ and &alpha;_s⁴ : explicit analytical results > We present analytical results both in momentum and position space for the massless correlators of the vector and scalar currents to order alpha_s^4 as well as for the tensor currents to order alpha_s^3. The evolution equations for the correlators together with all relevant anomalous dimensions are discussed in detail. As an application we present explicit conversion formulas relating the MSbar-renormalized vector, scalar and tensor currents to their counterparts renormalized in the X-space renormalization scheme more appropriate for lattice calculations.

In this talk we report on a study on the mixing of neutral charmed mesons and argue that, at the present stage, a CP violating weak phase of the order of some per mille can not be excluded in the Standard Model. It is shown how some, seemingly reasonable, simplifying assumptions about CKM couplings lead to the wrong conclusion that CP violation of this amount is an unambiguous indication of new physics. The presented results rely on a recent short-distance analysis of the Delta C=2 transition, which confirms the expectation that the dominant contribution is due to effects of flavour symmetry breaking appearing in higher orders of the Heavy Quark Expansion. We investigate meson-antimeson transitions with an intermediate state coupling to the meson's sea quark background, present in dimension 10 and 12, using a factorisation approach to simplify the operator basis. On account of a lifting of GIM suppression by one power of m_s/m_c, the contribution to y=DeltaGamma/2Gamma is found to exceed that of the formally leading dimension six by a factor close to ten.

Sector decomposition in its practical aspect is a constructive method used to evaluate Feynman integrals numerically. We present a new program performing the sector decomposition and integrating the expression afterwards. The program can be also used in order to expand Feynman integrals automatically in limits of momenta and masses with the use of sector decompositions and Mellin–Barnes representations. The program is parallelizable on modern multicore computers and even on multiple computers. Also we demonstrate some new numerical results for four-loop massless propagator master integrals.

The symbolic manipulation program FORM is specialized to handle very large algebraic expressions. Some specific features of its internal structure make FORM very well suited for parallelization.

We have now two parallel versions of FORM, one is based on POSIX threads and

is optimal for modern multicore computers while another one uses MPI and can be used to parallelize FORM on clusters and Massive Parallel Processing systems. Most existing FORM programs will be able to take advantage of the parallel execution without the need for modifications.

QCD/HQET matching for the heavy-quark field and heavy–light quark currents with three-loop accuracy is discussed.

Electroweak radiative corrections give rise to large negative, double-logarithmically enhanced corrections in the TeV region. These are partly compensated by real radiation and, moreover, affected by selecting isospin-noninvariant external states. We investigate the impact of real gauge boson radiation more quantitatively by considering different restricted final state configurations. We consider successively a massive abelian gauge theory, a spontaneously broken SU(2) theory and the electroweak Standard Model. We find that details of the choice of the phase space cuts, in particular whether a fraction of collinear and soft radiation is included, have a strong impact on the relative amount of real and virtual corrections.

The relation between the heavy-quark field in QCD and the corresponding field in HQET is derived up to three loops.

The old “glue–and–cut” symmetry of massless propagators, first established in [1], leads — after reduction to \ice{corresponding} master integrals is performed — to a host of non-trivial relations between the latter. The relations constrain the master integrals so tightly that they all can be analytically expressed in terms of only few, essentially trivial, watermelon-like integrals. As a consequence we arrive at explicit analytical results for all master integrals appearing in the process of reduction of massless propagators at three and four loops. The transcendental structure of the results suggests a clean explanation of the well-known mystery of the absence of even zetas ($\zeta_{2n}$) in the Adler function and other similar functions essentially reducible to massless propagators. Once a reduction of massless propagators at five loops is available, our approach should be also applicable for explicitly performing the corresponding five-loop master integrals.

We perform a next-to-next-to-leading order (NNLO) QCD analysis of the charm-top-quark contribution eta_ct to the effective Delta S = 2 Hamiltonian in the Standard Model. eta_ct represents an important part of the short distance contribution to the parameter epsilon_K. We calculate the three-loop anomalous dimension of the leading operator Q_S2, the three-loop mixing of the current-current and penguin operators into Q_S2, and the corresponding two-loop matching conditions at the electroweak, the bottom-quark, and the charm-quark scale. As our final numerical result we obtain eta_ct = 0.494 +/- 0.046, which is roughly 7% larger than the next-to-leading-order (NLO) value eta_ct(NLO) = 0.455 +/- 0.069. This results in a prediction for epsilon_K = (1.99 +/- 0.25) x 10^(-3), which corresponds to an enhancement of approximately 3.3% with respect to the value obtained using eta_ct(NLO).

The top-pair $t\bar t$ production cross section close to threshold in $e^+e^-$ collisions is strongly affected by the small lifetime of the top quark. Since the cross section is defined through final states containing the top decay products, a consistent definition of the cross section depends on prescriptions how these final states are accounted for the cross section. Experimentally, these prescriptions are implemented for example through cuts on kinematic quantities such as the reconstructed top quark invariant masses. As long as these cuts do not reject final states that can arise from the decay of a top and an anti-top quark with a small off-shellness compatible with the nonrelativistic power-counting, they can be implemented through imaginary phase space matching conditions in NRQCD. The prescription-dependent cross section can then be determined from the optical theorem using the $e^+e^-$ forward scattering amplitude. We compute the phase space matching conditions associated to cuts on the top and anti-top invariant masses at next-to-next-to-leading logarithmic (NNLL) order and partially at next-to-next-to-next-to-leading logarithmic (N${}^3$LL) order in the nonrelativistic expansion and, together with finite lifetime and electroweak effects known from previous work, analyze their numerical impact on the $t\bar t$ cross section. We show that the phase space matching contributions are essential to make reliable NRQCD predictions, particularly for energies below the peak region, where the cross section is small. We find that irreducible background contributions associated to final states that do not come from top decays are strongly suppressed and can be neglected for the theoretical predictions.

We report on our calculation of the order alpha_s^4 contributions to the Bjorken sum rule for polarized electron-nucleon scattering and to the (non-singlet) part of the cross section for electron-positron annihilation into hadrons for the case of a generic colour gauge group. We confirm at the same order a (generalized) Crewther relation between the Bjorken sum rule and the corresponding Adler function which provides a strong test of the correctness of our previously obtained results: the ratio R(s) in QCD and the five-loop beta-function in quenched QED.

We review recent progress in the perturbative calculations for semileptonic and hadronic B meson decays with an emphasis on the phenomenological implications of the next-to-next-to-leading order (NNLO) corrections. Specifically, we consider CP-averaged branching ratios of tree-dominated B → pi pi/pi rho/rho rho decays and the inclusive determination of |V_ub| from B → X_u l nu.

Using the radiative return method, experiments at high luminosity electron-positron colliders allow to explore the kaon and the pion form factors in the time-like region up to fairly high energies. This opens the possibility to study kaon and pion pair production at and around the narrow resonances J/psi and psi(2S) and explore the interference between electromagnetic and hadronic amplitudes. Parameterizations of charged and neutral kaon as well as pion form factors are derived, which lead to an improved description of the data in the region of large invariant masses of the meson pair. These form factors are combined with the hadronic couplings of charged and neutral kaons to J/psi and psi(2S) and implemented into the Monte Carlo generator PHOKHARA, which is now, for the first time, able to simulate the production of narrow resonances and their decay into kaon, pion and muon pairs.

Recent theoretical and experimental improvements in the determination of charm and bottom quark masses are discussed. The final results, $m_c(3\,\text{GeV})=986(13)\,$MeV and $m_b(m_b)=4163(16)\,$MeV represent, together with a closely related lattice determination $m_c(3\;{\rm GeV})=986(10)\,$MeV, the presently most precise determinations of these two fundamental Standard Model parameters. A critical analysis of the theoretical and experimental uncertainties is presented.

The high energy behaviour of electroweak corrections to gauge boson pair production at LHC can be derived in the framework of evolution equations up to NNLL contributions to all order in perturbation theory. On the basis of this general result we derive the one- and two-loop cross section in NNLL approximation for W-pair production at partonic and hadronic level.

We present the complete two-loop electroweak corrections to $gg\to H$, the main partonic channel for the production of the Higgs boson at hadron colliders. The evaluation is based on a numerical approach and the result covers all kinematical regions, including $WW$ and $ZZ$ thresholds, by introducing complex masses for the $W$ and the $Z$ bosons. Furthermore the relation between physical observables measured at LHC and Tevatron and Higgs pseudo-observables (production cross section and partial decay widths) is revised by extensively using the notion of the Higgs complex pole. Numerical effects for the Higgs production cross section are presented.

We present the achievements of the last years of the experimental and theoretical groups working on hadronic cross section measurements at the low energy e+e- colliders in Beijing, Frascati, Ithaca, Novosibirsk, Stanford and Tsukuba and on tau decays. We sketch the prospects in these fields for the years to come. We emphasise the status and the precision of the Monte Carlo generators used to analyse the hadronic cross section measurements obtained as well with energy scans as with radiative return, to determine luminosities and tau decays. The radiative corrections fully or approximately implemented in the various codes and the contribution of the vacuum polarisation are discussed.

We compute, for the first time, the order alpha_s^4 contributions to the Bjorken sum rule for polarized electron-nucleon scattering and to the (non-singlet) Adler function for the case of a generic colour gauge group. We confirm at the same order a (generalized) Crewther relation which provides a strong test of the correctness of our previously obtained results: the QCD Adler function and the five-loop \beta-function in quenched QED. In particular, the appearance of an irrational contribution proportional to zeta_3 in the latter quantity is confirmed. We obtain the {\em commensurate} scale equation relating the effective strong coupling constants as inferred from the Bjorken sum rule and from the Adler function at order alpha_s^4.

The relation between physical observables measured at LHC and Tevatron and standard model Higgs pseudo-observables (production cross section and partial decay widths) is revised by extensively using the notion of the Higgs complex pole on the second Riemann sheet of the $S $-matrix. The extension of their definition to higher orders is considered, confronting the problems that arise when QED(QCD) corrections are included in computing realistic observables. Numerical results are presented for pseudo-observables related to the standard model Higgs boson decay and production. The relevance of the result for exclusion plots of the standard model Higgs boson for high masses (up to $600 $GeV) is discussed. Furthermore, a recipe for the analytical continuation of Feynman loop integrals from real to complex internal masses and complex Mandelstam invariants is thoroughly discussed.

The three-loop corrections to the potential of two heavy quarks are computed. Analytic results for the most complicated master integrals are presented.

We describe recent evaluations of three-loop vertex corrections which have been performed in the context of different physical applications: the massless quark and gluon form factor, the vector current matching coefficient between QCD and NRQCD, and the virtual corrections of the gluon-Higgs coupling with finite top quark mass.

In this talk we discuss the next-to-leading-order electroweak (EW) corrections to W-boson + jet hadroproduction [1] and compare the full result to a simple approximation assuming factorization of EW and QCD corrections for the charged-current Drell-Yan process. The W-boson resonance is treated consistently using the complex-mass scheme, and all off-shell effects are taken into account. The corresponding next-to-leading-order QCD corrections have also been recalculated. All the results are implemented in a flexible Monte Carlo code. Selected numerical results for this Standard Model benchmark process are presented for the LHC. The comparison of our result to an approximation based on the EW corrections to W-boson production without additional jets is a step towards a better understanding of the interplay between QCD and EW effects for W-boson production in general.