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TTP05-29 Strange Quark Mass from Pseudoscalar Sum Rule with O(alpha_s^4) Accuracy

TTP05-29 Strange Quark Mass from Pseudoscalar Sum Rule with O(alpha_s^4) Accuracy

We include the new, five-loop, O(alpha_s^4) correction into the QCD sum rule used for the s-quark mass determination. The pseudoscalar Borel sum rule is taken as a study case. The OPE for the correlation function with N^4LO, O(alpha_s^4) accuracy in the perturbative part, and with dimension ⇐ 6 operators reveals a good convergence. We observe a significant improvement of stability of the sum rule with respect to the variation of the renormalization scale after including the O(alpha_s^4) correction. We obtain the interval m_s(2 GeV)=105 \pm 6 \pm 7 MeV, which exhibits about 2 MeV increase of the central value, if the $O(alpha_s^4) terms are removed.

K.G. Chetyrkin and A.~Khodjamirian
Eur. Phys. J. C46 721-728 2006
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TTP05-28 Electron-positron annihilation into three pions and the radiative return.

TTP05-28 Electron-positron annihilation into three pions and the radiative return.

Abstract: The Monte Carlo event generator PHOKHARA, which simulates hadron

and muon production
at electron-positron colliders through radiative return, has been extended
to final states with three pions. A model for the form factor based
on generalized vector dominance has been employed, which is consistent
with presently available experimental observations.
Henryk Czyz, Agnieszka Grzelinska, Johann H. K\„uhn, German Rodrigo
Eur.Phys.J.C 47 617-624 2006
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TTP05-27 QCD Decoupling at Four Loops

TTP05-27 QCD Decoupling at Four Loops

We present the matching condition for the strong coupling constant alpha_s at a heavy quark threshold to four loops in the modified minimal subtraction scheme. Our results lead to further decrease of the theoretical uncertainty of the evolution of the strong coupling constant through heavy quark thresholds. Using a low energy theorem we furthermore derive the effective coupling of the Higgs boson to gluons (induced by a virtual heavy quark) in four- and (partially) through five-loop approximation.

K.G. Chetyrkin, J.H. K\„uhn and C. Sturm
Nucl.Phys. B744 121-135 2006
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TTP05-26 Two-loop O(alpha alpha_s) corrections to the on-shell fermion propagator in the Standard Model

TTP05-26 Two-loop O(alpha alpha_s) corrections to the on-shell fermion propagator in the Standard Model

In this paper we consider mixed two-loop electroweak corrections to the top quark propagator in the Standard Model. In particular, we compute the on-shell renormalization constant for the mass and wave function, which constitute building blocks for many physical processes. The results are expressed in terms of master integrals. For the latter practical approximations are derived. In the case of the mass renormalization constant we find agreement with the results in the literature.

D.Eiras and M.Steinhauser
JHEP 02 010 2006
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TTP05-25 Quark mixing and CP violation - the CKM matrix

TTP05-25 Quark mixing and CP violation - the CKM matrix

I present the status of the elements and parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix and summarise the related theoretical progress since „Lepton-Photon 2003“. One finds |V_{us}| = 0.2227 +/- 0.0017 from K and tau decays and |V_{cb}| = (41.6 +/- 0.5) * 10^{-3} from inclusive semileptonic B decays. The unitarity triangle can now be determined from tree-level quantities alone and the result agrees well with the global fit including flavour-changing neutral current (FCNC) processes, which are sensitive to new physics. From the global fit one finds the three CKM angles theta_{12}=12.9 +/- 0.1 degrees, theta_{23}= 2.38 +/- 0.03 degrees and theta_{13}= 0.223 +/- 0.007 degrees in the standard PDG convention. The CP phase equals delta_{13} = gamma = (58.8 +5.3/-5.8) degrees at 1 sigma CL and gamma=(58.8 +11.2/-15.4) degrees at 2 sigma CL. A major progress are first results from fully unquenched lattice QCD computations for the hadronic quantities entering the UT fit. I further present the calculation of three-loop QCD corrections to the charm contribution in K+ → pi+ nu nu-bar decays, which removes the last relevant theoretical uncertainty from the K → pi nu nu-bar system. Finally I discuss mixing-induced CP asymmetries in b → s q-bar q penguin decays, whose naive average is below its Standard Model value by 3 sigma.

Ulrich Nierste
Int.J.Mod.Phys. A21 1724-1737 2006
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TTP05-24 Recent progress in computing four-loop massive correlators

TTP05-24 Recent progress in computing four-loop massive correlators

We report about recent progress in computing four-loop massive correlators. The expansion of these correlators in the external momentum leads to vacuum integrals. The calculation of these vacuum integrals can be used to determine Taylor expansion coefficients of the vacuum polarization function and decoupling functions in perturbative Quantum chromodynamics. New results at four-loop order for the lowest Taylor expansion coefficient of the vacuum polarization function and for the decoupling relation are presented.

K.G. Chetyrkin, J.H. K\„uhn and C. Sturm
Nucl.Phys.(Proc.Suppl.) B164 203-206 2007
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TTP05-23 Threshold resummation for high-transverse-momentum Higgs production at the LHC
D. de Florian, A. Kulesza and W. Vogelsang
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TTP05-22 On the spectra of atoms and hadrons

TTP05-22 On the spectra of atoms and hadrons

For relativistic closed systems, an operator is explained which has as stationary eigenvalues the squares of the total cms energies, while the wave function has only half as many components as the corresponding Dirac wave function. The operator's time dependence is generalized to a Klein-Gordon equation. It ensures relativistic kinematics in radiative decays. The new operator is not hermitian.

Hartmut Pilkuhn
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TTP05-21 Four-Loop Decoupling Relations for the Strong Coupling

TTP05-21 Four-Loop Decoupling Relations for the Strong Coupling

We compute the matching relation for the strong coupling constant

 within the framework of QCD up to four-loop order.
 This allows a consistent five-loop running (once the $\beta$
 function is available to this order) taking into account threshold effects.
 As a side product we obtain the effective coupling of a Higgs boson
 to gluons with five-loop accuracy.
Y. Schroder and M. Steinhauser
JHEP 0601 051 2006
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TTP05-20 Radiative return method as a tool in hadronic physics

TTP05-20 Radiative return method as a tool in hadronic physics

A short review of both theoretical and experimental aspects

of the radiative return method is presented. It is emphasised
that the method gives not only possibility of the independent
from the scan method measurement of the hadronic cross section,
but also can provide information concerning details of the hadronic
interactions. New developments in the PHOKHARA event generator
are also reviewed. The 3 pion and kaon pair production is implemented
within the version 5.0 of the program, together with contributions
of the radiative $\phi$ decays to the 2 pion final states.
Missing NLO radiative corrections to the $e^+e^- \to \mu^+\mu^- \gamma$
process will be implemented in the forthcoming version of the generator.
Henryk Czyz, Agnieszka Grzelinska i E. Nowak-Kubat
Acta Phys. Polon. B 36 3403-3412 2005
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TTP05-19 Summing next-to-next-to-leading logarithms in b-

TTP05-19 Summing next-to-next-to-leading logarithms in b-

c transitions at zero recoil > The HQET-1 → HQET-2 matching coefficient for the b→c currents at zero recoil has been found with two-loop accuracy. The next-to-next-to-leading logarithms has been summed in the leading order in m_c/m_b. Higher-order corrections are estimated in the large-\beta_0 limit.

Andrey Grozin
PDF PostScript arXiv

TTP05-18 Higgs production and decay: Analytic results at next-to-leading order QCD

TTP05-18 Higgs production and decay: Analytic results at next-to-leading order QCD

The virtual two-loop corrections for Higgs production in gluon fusion are calculated analytically in QCD for arbitrary Higgs and quark masses. Both scalar and pseudo-scalar Higgs bosons are considered. The results are obtained by expanding the known one-dimensional integral representation in terms of m_H/m_q, and matching it with a suitably chosen ansatz of Harmonic Polylogarithms. This ansatz is motivated by the known analytic result for the Higgs decay rate into two photons. The method also allows us to check this result and to extend it to the pseudo-scalar decay rate.

Robert V. Harlander and Philipp Kant
JHEP 0512 015 2005
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TTP05-17 Two-Loop Electroweak Logarithms in Four-Fermion Processes at High Energy

TTP05-17 Two-Loop Electroweak Logarithms in Four-Fermion Processes at High Energy

We present the complete analytical result for the two-loop logarithmically enhanced contributions to the high energy asymptotic behavior of the vector form factor and the four-fermion cross section in a spontaneously broken SU(2) gauge model. On the basis of this result we derive the dominant two-loop electroweak corrections to the neutral current four-fermion processes at high energies. Previously neglected effects of the gauge boson mass difference are included through the next-to-next-to-leading logarithmic approximation.

B. Jantzen, J.H. K\„uhn, A.A. Penin, V.A. Smirnov
Nucl.Phys. B731 188-212 2005 Erratum-ibid. B752 (2006) 327-328
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TTP05-16 Electroweak corrections to hadronic photon production at large transverse momenta

TTP05-16 Electroweak corrections to hadronic photon production at large transverse momenta

We study the impact of electroweak radiative corrections on direct production of photons with high transverse momenta at hadron colliders. Analytic results for the weak one-loop corrections to the parton scattering reaction $\bar q q \to \gamma g$ and its crossed variants are presented. For the high-energy region, where the corrections are strongly enhanced by logarithms of $\hat s/M_W^2$, we derive simple asymptotic expressions which approximate the exact one-loop results with high precision. The dominant two-loop electroweak contributions are also calculated. Numerical results are presented for the LHC and the Tevatron. The corrections are negative and their size increases with transverse momentum. For the LHC, where transverse momenta of 2 TeV or more can be reached, the size of the one- and two-loop effects amounts up to -17\% and +3\%, respectively. At the Tevatron, with transverse momenta up to 400 GeV, the one-loop corrections do not exceed -4\% and the two-loop effects are negligible. Finally we compare the cross sections for hadronic production of photons and Z bosons and find that the electroweak corrections have an important impact on their ratio.

Johann H. K\„uhn, A. Kulesza, S. Pozzorini, M. Schulze
JHEP 0603 059 2006
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TTP05-15 Lectures on QED and QCD

TTP05-15 Lectures on QED and QCD

The lectures are a practical introduction to perturbative calculations in QED and QCD. I discuss methods of calculation of one- and two-loop diagrams in dimensional regularization, MSbar and on-shell renormalization schemes, decoupling of heavy-particle loops.

A.G. Grozin
PDF PostScript arXiv

TTP05-14 Two-Loop matching coefficients for the strong coupling in the MSSM

TTP05-14 Two-Loop matching coefficients for the strong coupling in the MSSM

When relating the strong coupling $\alpha_s$, measured at the scale of the $Z$ boson mass, to its numerical value at some higher energy, for example the scale of Grand Unification, it is important to include higher order corrections both in the running of $\alpha_s$ and the decoupling of the heavy particles. We compute the two-loop matching coefficients for $\alpha_s$ within the Minimal Supersymmetric Standard Model (MSSM) which are necessary for a consistent three-loop evolution of the strong coupling constant. Different scenarios for the hierarchy of the supersymmetric scales are considered and the numerical effects are discussed. We find that the three-loop effects can be as large as and sometimes even larger than the uncertainty induced by the current experimental accuracy of $\alpha_s(M_Z)$.

R. Harlander, L. Mihaila, M. Steinhauser
Phys. Rev. D 72 095009 2005
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TTP05-13 Two-Loop Photonic Corrections to Massive Bhabha Scattering

TTP05-13 Two-Loop Photonic Corrections to Massive Bhabha Scattering

We describe the details of the evaluation of the two-loop radiative photonic corrections to Bhabha scattering. The role of the corrections in the high-precision luminosity determination at present and future electron-positron colliders is discussed.

A.A. Penin
Nucl.Phys. B734 185-202 2006
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TTP05-12 Electroweak corrections to top quark pair production in quark-antiquark annihilation

TTP05-12 Electroweak corrections to top quark pair production in quark-antiquark annihilation

Top-quark physics plays an important r\^ole at hadron colliders such as the Tevatron at Fermilab or the LHC at CERN. Given the planned precision at these colliders, precise theoretical predictions are required. In this paper we present the complete electroweak corrections to QCD-induced top-quark pair production in quark–antiquark annihilation. In particular we provide compact analytic expressions for the differential partonic cross section, which will be useful for further theoretical investigations.

J.H. K\„uhn, A. Scharf, P. Uwer
Eur.Phys.J. C45 139-150 2006
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TTP05-11 Scalar Correlator at alpha_s^4, Higgs Decay into b-quarks and Bounds on the Light Quark Masses

TTP05-11 Scalar Correlator at alpha_s^4, Higgs Decay into b-quarks and Bounds on the Light Quark Masses

We compute, for the first time, the absorptive part of the massless correlator of two quark scalar currents in five loops. As physical applications we consider the O(alpha_s^4) corrections to the decay rate of the Standard Model Higgs boson into quarks, as well as the constraints on the strange quark mass following from QCD sum rules.

P.A. Baikov, K.G. Chetyrkin and J.H. K\„uhn
.Phys. Rev. Lett. 96 012003 2006
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TTP05-10 One-loop weak corrections to hadronic production of Z bosons at large transverse momenta

TTP05-10 One-loop weak corrections to hadronic production of Z bosons at large transverse momenta

To match the precision of present and future measurements of Z-boson production at hadron colliders, electroweak radiative corrections must be included in the theory predictions. In this paper we consider their effect on the transverse momentum ($p_T$) distribution of Z bosons, with emphasis on large $p_T$. We evaluate, analytically and numerically, the full one-loop corrections for the parton scattering reaction $q\bar q \to Z g$ and its crossed variants. In addition we derive compact approximate expressions which are valid in the high-energy region, where the weak corrections are strongly enhanced by logarithms of $\hat s/M_W^2$. These expressions include quadratic and single logarithms as well as those terms that are not logarithmically enhanced. This approximation, which confirms and extends earlier results obtained to next-to-leading logarithmic accuracy, permits to reproduce the exact one-loop corrections with high precision. Numerical results are presented for proton-proton and proton-antiproton collisions. The corrections are negative and their size increases with $p_T$. For the Tevatron they amount up to -7\% at 300 GeV. For the LHC, where transverse momenta of 2 TeV or more can be reached, corrections up to -40\% are observed. We also include the dominant two-loop effects of up to 8\% in our final LHC predictions.

J. H. K\„uhn, A. Kulesza, S. Pozzorini, M. Schulze
Nucl. Phys. B 727 368-394 2005
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TTP05-09 Corrections of order $\beta_0^3\alpha_s^3$ to the energy levels and wave function

TTP05-09 Corrections of order $\beta_0^3\alpha_s^3$ to the energy levels and wave function

One of the most important tasks of a future linear collider is the

 precise measurement of the threshold production cross section of top
 quark pairs. In order to match the expected experimental precision
 it is necessary to perform theoretical predictions which include
 corrections up to third order in perturbation theory. In this contribution
 we report about the corrections of order $\beta_0^3\alpha_s^3$ to the
 heavy quark spectrum and wave function. Physical applications both for
 the top and bottom quark system are discussed.
Matthias Steinhauser
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TTP05-08 Calculation of Massless Feynman Integrals using Harmonic Sums

TTP05-08 Calculation of Massless Feynman Integrals using Harmonic Sums

A method for the evaluation of the epsilon expansion of multi-loop massless Feynman integrals is introduced. This method is based on the Gegenbauer polynomial technique and the expansion of the Gamma function in terms of harmonic sums. Algorithms for the evaluation of nested and harmonic sums are used to reduce the expressions to get analytical or numerical results for the expansion coefficients. Methods to increase the precision of numerical results are discussed.

Stefan Bekavac
Comput. Phys. Commun. 175 180-195 2006
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TTP05-07 Pseudo-scalar Higgs production at next-to-leading order SUSY-QCD

TTP05-07 Pseudo-scalar Higgs production at next-to-leading order SUSY-QCD

The production rate of the CP-odd Higgs boson in the Minimal Supersymmetric Standard Model is evaluated through next-to-leading order in the strong coupling constant. The divergent integrals are regulated using Dimensional Reduction, with a straightforward implementation of $\gamma_5$. The well-known Standard Model result is recovered in this scheme through a cancellation between the quark and squark contributions as the masses of the supersymmetric particles tend to infinity.

Robert V. Harlander and Franziska Hofmann
JHEP 0603 050 2006
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TTP05-06 Precise numerical evaluation of the two loop sunrise graph Master Integrals in the equal mass case.

TTP05-06 Precise numerical evaluation of the two loop sunrise graph Master Integrals in the equal mass case.

We present a double precision routine in Fortran for the precise and fast numerical evaluation of the two Master Integrals (MIs) of the equal mass two-loop sunrise graph for arbitrary momentum transfer in d=2 and d=4 dimensions. The routine implements the accelerated power series expansions obtained by solving the corresponding differential equations for the MIs at their singular points. With a maximum of 22 terms for the worst case expansion a relative precision of better than a part in 10^{15} is achieved for arbitrary real values of the momentum transfer.

S. Pozzorini and E. Remiddi
Comput.Phys.Commun. 175 381-387 2006
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TTP05-05 Energy-square equations for relativistic closed systems.

TTP05-05 Energy-square equations for relativistic closed systems.

The most powerful relativistic two-body equations have only half as many components as their Dirac-Breit and Bethe-Salpeter counterparts and contain only the square of the total cms energy. In this letter, the „energy-square“ theorem is extended to systems of $n>2$ Dirac particles. The case $n=3$ is discussed for baryons.

Hartmut Pilkuhn
Physics Letters B 614 62-65 2005
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TTP05-04 Two-Loop Electroweak Logarithms

TTP05-04 Two-Loop Electroweak Logarithms

We present the complete analytical result for the two-loop logarithmically enhanced contributions to the high energy asymptotic behavior of the vector form factor and the four-fermion cross section in a spontaneously broken SU(2) gauge model. On the basis of this result we derive the dominant two-loop electroweak corrections to the neutral current four-fermion processes at high energies.

Bernd Jantzen, Johann H. K\„uhn, Alexander A. Penin, Vladimir A. Smirnov
Phys.Rev. D72 051301 2006
PDF PostScript arXiv

TTP05-03 Four-Loop Singlet Contribution to the $\rho$ Parameter

TTP05-03 Four-Loop Singlet Contribution to the $\rho$ Parameter

We compute the four-loop contribution to the electroweak $\rho$

 parameter induced by the singlet diagrams of the $Z$-boson
 self-energy. The numerical impact on the weak mixing angle and the
 $W$-boson mass is small.
Y. Schr\„oder, M. Steinhauser
Phys. Lett. B 622 124-130 2005
PDF PostScript arXiv

TTP05-02 Two-Loop Corrections to Bhabha Scattering

TTP05-02 Two-Loop Corrections to Bhabha Scattering

The two-loop radiative photonic corrections to the Bhabha scattering are computed in the leading order of the small electron mass expansion up to nonlogarithmic term. After including the soft photon bremsstrahlung we obtain the infrared finite result for the differential cross section, which can be directly applied to precise luminosity determination of the present and future $e^+e^-$ colliders.

A.A. Penin
Phys.Rev.Lett. 95 010408-010412 2005
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TTP05-01 Heavy Quarkonium Spectrum and Production/Annihilation Rates to order $\beta_0^3\alpha_s^3$

TTP05-01 Heavy Quarkonium Spectrum and Production/Annihilation Rates to order $\beta_0^3\alpha_s^3$

We compute the third-order corrections to the heavy quarkonium

 spectrum and production/annihilation rates due to the leading
 renormalization group running of the static potential.  The previously
 known complete ${\cal O}(m_q\alpha_s^5)$ result for the heavy
 quarkonium ground state energy is extended to the exited states.
 After including the ${\cal O}(\alpha_s^3)$ corrections the
 perturbative results are in surprisingly good agreement with the
 experimental data on the masses of the excited $\Upsilon$ resonances
 and the leptonic width of the $\Upsilon(1S)$ meson. The impact of the
 corrections on the $\Upsilon$ sum rules and top quark-antiquark
 threshold production cross section is also discussed.
A.A. Penin, V.A. Smirnov, M. Steinhauser
Nucl.Phys. B716 303-318 2005
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