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Matthias Steinhauser

Publications and source records attributed to Matthias Steinhauser.

At least 127 records · Page 7Linked to original sources
arXiv2014

Hadronic contribution to the muon anomalous magnetic moment to next-to-next-to-leading order

We compute the next-to-next-to-leading order hadronic contribution to the muon anomalous magnetic moment originating from the photon vacuum polarization. The corresponding three-loop kernel functions are calculated using asymptotic expansion techniques which lead to analytic expressions. Our final result, $a_μ^{\rm had,NNLO} = 1.24 \pm 0.01 \times 10^{-10}$, has the same order of magnitude as the current uncertainty of the leading order hadronic contribution and should thus be included in future analyses.

hep-ph↗
arXiv2014

B_{s,d} -> l+ l- in the Standard Model with Reduced Theoretical Uncertainty

We combine our new results for the O(alpha_em) and O(alpha_s^2) corrections to B_{s,d} -> l^+ l^-, and present updated branching ratio predictions for these decays in the standard model. Inclusion of the new corrections removes major theoretical uncertainties of perturbative origin that have just begun to dominate over the parametric ones. For the recently observed muonic decay of the B_s meson, our calculation gives BR(B_s -> mu^+ mu^-) = (3.65 +_ 0.23) * 10^(-9).

hep-ph↗
arXiv2014

Three-loop matching of the vector current

We evaluate the three-loop corrections to the matching coefficient of the vector current between Quantum Chromodynamics (QCD) and non-relativistic QCD. The result is presented in the MSbar scheme where large perturbative corrections are observed. The implications on the threshold production of top quark pairs are briefly discussed.

hep-ph↗
arXiv2014

Leptonic decay of the Upsilon(1S) meson at third order in QCD

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

hep-ph↗
arXiv2013

Towards analytic $(g-2)_μ$ at four loops

In this contribution we present recent four-loop results for the muon anomalous magnetic moment based on analytic methods. In particular, fermionic corrections involving two or more closed electron loops or at least one tau lepton loop are discussed.

hep-ph↗
arXiv2013

Anomalous magnetic moment with heavy virtual leptons

We compute the contributions to the electron and muon anomalous magnetic moment induced by heavy leptons up to four-loop order. Asymptotic expansion is applied to obtain three analytic expansion terms which show rapid convergence.

hep-ph↗
arXiv2013

Three-loop QCD corrections to B_s -> mu^+ mu^-

The decay B_s -> mu^+ mu^- in the Standard Model is generated by the well-known W-box and Z-penguin diagrams that give rise to an effective quark-lepton operator Q_A at low energies. We compute QCD corrections of order alpha_s^2 to its Wilson coefficient C_A. It requires performing three-loop matching between the full and effective theories. Including the new corrections makes C_A more stable with respect to the matching scale mu_0 at which the top-quark mass and alpha_s are renormalized. The corresponding uncertainty in |C_A|^2 gets reduced from around 1.8% to less than 0.2%. Our results are directly applicable to all the B_{s(d)} -> l^+ l^- decay modes.

hep-ph↗
arXiv2013

Renormalization constants and beta functions for the gauge couplings of the Standard Model to three-loop order

We compute the beta functions for the three gauge couplings of the Standard Model in the minimal subtraction scheme to three loops. We take into account contributions from all sectors of the Standard Model. The calculation is performed using both Lorenz gauge in the unbroken phase of the Standard Model and background field gauge in the spontaneously broken phase. Furthermore, we describe in detail the treatment of $γ_5$ and present the automated setup which we use for the calculation of the Feynman diagrams. It starts with the generation of the Feynman rules and leads to the bare result for the Green's function of a given process.

hep-ph↗
arXiv2013

Colour octet potential to three loops

We consider the interaction between two static sources in the colour octet configuration and compute the potential to three loops. Special emphasis is put on the treatment of pinch contributions and two methods are applied to reduce their evaluation to diagrams without pinches.

hep-ph↗
arXiv2013

MT: a Mathematica package to compute convolutions

We introduce the \prog{Mathematica} package \prog{MT} which can be used to compute, both analytically and numerically, convolutions involving harmonic polylogarithms, polynomials or generalized functions. As applications contributions to next-to-next-to-next-to leading order Higgs boson production and the Drell-Yan process are discussed.

hep-ph↗
arXiv2013

Higgs boson production in the SM and MSSM to NNLO and beyond

In this contribution a brief review about the status of higher order corrections to Higgs boson production within the Minimal Supersymmetric Standard Model (MSSM) is given. Furthermore the first activities towards third-order corrections in the Standard Model (SM) are discussed.

hep-ph↗
arXiv2013

Two-loop static potential in N=4 supersymmetric Yang-Mills theory

We compute the soft contribution to the static energy of two heavy colour sources interacting via a N=4 supersymmetric Yang-Mills theory. Both singlet and octet colour configurations are considered. Our calculations complete recent considerations of the ultrasoft contributions.

hep-th↗
arXiv2013

On the Higgs boson pair production at the LHC

We compute the production cross section of a pair of Standard Model Higgs bosons at the LHC at next-to-leading order in QCD, including corrections in inverse powers of the top quark mass. We calculate these power corrections through ${\cal O}(1/M_t^8)$ and study their relevance for phenomenology of the double Higgs production. We find that power corrections are significant, even for moderate values of partonic center-of-mass energies, and that convergence of the $1/M_t$ expansion can be dramatically improved by factorizing the leading order cross section with full $M_t$-dependence.

hep-ph↗
arXiv2013

Four-loop corrections with two closed fermion loops to fermion self energies and the lepton anomalous magnetic moment

We compute the eighth-order fermionic corrections involving two and three closed massless fermion loops to the anomalous magnetic moment of the muon. The required four-loop on-shell integrals are classified and explicit analytical results for the master integrals are presented. As further applications we compute the corresponding four-loop QCD corrections to the mass and wave function renormalization constants for a massive quark in the on-shell scheme.

hep-ph↗
arXiv2012

Higgs boson production at the LHC: NNLO partonic cross sections through order $ε$ and convolutions with splitting functions to N$^3$LO

We consider Higgs boson production at hadron colliders in the gluon fusion channel and compute higher order terms in the regularization parameter $ε$. In particular, the next-to-next-to-leading order cross section is evaluated including order $ε$ terms. These results are used to compute all convolutions with the splitting functions entering the next-to-next-to-next-to-leading order cross section.

hep-ph↗
arXiv2012

$\bar{B}\to X_s γ$ in the Two Higgs Doublet Model up to Next-to-Next-to-Leading Order in QCD

We compute three-loop matching corrections to the Wilson coefficients $C_7$ and $C_8$ in the Two Higgs Doublet Model by applying expansions for small, intermediate and large charged Higgs boson masses. The results are used to evaluate the branching ratio of $\bar{B}\to X_s γ$ to next-to-next-to leading order accuracy, and to determine an updated lower limit on the charged Higgs boson mass. We find $\mhplus \ge 380 $GeV at 95% confidence level when the recently completed BABAR data analysis is taken into account. Our results for the charged Higgs contribution to the branching ratio exhibit considerably weaker sensitivity to the matching scale $μ_0$, as compared to previous calculations.

hep-ph↗