792 research outputs found
Higher-order hadronic and heavy-lepton contributions to the anomalous magnetic moment
We report about recent results obtained for the muon anomalous magnetic
moment. Three-loop kernel functions have been computed to obtain the
next-to-next-to-leading-order hadronic vacuum polarization contributions. The
numerical result, , is of
the same order of magnitude as the current uncertainty from the hadronic
contributions. For heavy-lepton corrections, analytical results are obtained at
four-loop order and compared with the known results.Comment: Contribution to the proceedings of Loops and Legs in Quantum Field
Theory, 27 April - 2 May 2014, Weimar, German
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,
, has the same order of
magnitude as the current uncertainty of the leading order hadronic contribution
and should thus be included in future analyses.Comment: 9 pages,v2: note on NLO hadronic light-by-light contribution added,
matches published version, Physics Letters B 734 (2014) 144-14
Massive three loop form factors in the planar limit
We present the color planar and complete light quark QCD contributions to the
three loop heavy quark form factors in the case of vector, axial-vector, scalar
and pseudo-scalar currents. We evaluate the master integrals applying a new
method based on differential equations for general bases, which is applicable
for any first order factorizing systems. The analytic results are expressed in
terms of harmonic polylogarithms and real-valued cyclotomic harmonic
polylogarithms.Comment: 10 pages; Proceedings of the Loops and Legs in Quantum Field Theory,
29th April 2018 - 4th May 2018, St. Goar, Germany; Report number modifie
The three-loop cusp anomalous dimension in QCD
We present the full analytic result for the three-loop angle-dependent cusp
anomalous dimension in QCD. With this result, infrared divergences of planar
scattering processes with massive particles can be predicted to that order.
Moreover, we define a closely related quantity in terms of an effective
coupling defined by the light-like cusp anomalous dimension. We find evidence
that this quantity is universal for any gauge theory, and use this observation
to predict the non-planar -dependent terms of the four-loop cusp
anomalous dimension.Comment: 5 pages, 2 figure
Hyperfine splitting in positronium to : one-photon annihilation contribution
We present the complete result for the one-photon
annihilation contribution to the hyperfine splitting of the ground state energy
levels in positronium. Numerically it increases the prediction of quantum
electrodynamics by kHz.Comment: 5 pages, 2 figure
Four-loop relation between the and on-shell quark mass
In this contribution we discuss the four-loop relation between the on-shell
and definition of heavy quark masses which is applied to the
top, bottom and charm case. We also present relations between the quark mass and various threshold mass definitions and discuss the
uncertainty at next-to-next-to-next-to-leading order.Comment: 9 pages, 2 figures, to appear in the proceedings of the 12th
International Symposium on Radiative Corrections (Radcor 2015) and LoopFest
XIV (Radiative Corrections for the LHC and Future Colliders
Quark mass relations to four-loop order
We present results for the relation between a heavy quark mass defined in the
on-shell and scheme to four-loop order. The method to compute
the four-loop on-shell integral is briefly described and the new results are
used to establish relations between various short-distance masses and the
quark mass to next-to-next-to-next-to-leading order accuracy.
These relations play an important role in the accurate determination of the
heavy quark masses.Comment: 6 pages, v2: references added, typos in eq.(16) fixed, matches
published versio
The terms of the three-loop cusp anomalous dimension in QCD
In this talk we present the result for the dependent piece of the
three-loop cusp anomalous dimension in QCD. Remarkably, it is parametrized by
the same simple functions appearing in analogous anomalous dimensions in
SYM at one and two loops. We also compute all required master
integrals using a recently proposed refinement of the differential equation
method. The analytic results are expressed in terms of harmonic polylogarithms
of uniform weight.Comment: 8 pages, 2 figures; v2: typo in eq. (4.4) fixed, 'three-loop' added
to titl
at four loops in QED
We review the four-loop QED corrections to the anomalous magnetic moment of
the muon. The fermionic contributions with closed electron and tau
contributions are discussed. Furthermore, we report on a new independent
calculation of the universal four-loop contribution and compare with existing
results.Comment: 6 pages, Contribution to the proceedings of the International
workshop on e+e- collisions from Phi to Psi 2017, v2: references adde
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