1,747 research outputs found
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
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
-on-shell quark mass relation up to four loops in QCD and a general SU gauge group
In this paper we compute the relation between heavy quark masses defined in
the modified minimal subtraction and on-shell scheme. Detailed results are
presented for all coefficients of the SU colour factors. The reduction
of the four-loop on-shell integrals is performed for a general QCD gauge
parameter. Some of the about 380 master integrals are computed analytically,
others with high numerical precision based on Mellin-Barnes representations,
and the rest numerically with the help of {\tt FIESTA}. We discuss in detail
the precise numerical evaluation of the four-loop master integrals. Updated
relations between various short-distance masses and the
quark mass to next-to-next-to-next-to-leading order accuracy are provided for
the charm, bottom and top quark. We discuss the dependence on the
renormalization and factorization scale.Comment: 53 pages, 11 figures, v2: minor changes, references added,
corresponds to published versio
Matching the heavy-quark fields in QCD and HQET at four loops
The QCD/HQET matching coefficient for the heavy-quark field is calculated up
to four loops. It must be finite; this requirement produces analytical results
for some terms in the four-loop on-shell heavy-quark field renormalization
constant which were previously only known numerically. The effect of a non-zero
lighter-flavor mass is calculated up to three loops. A class of on-shell
integrals with two masses is analyzed in detail. By specifying our result to
QED, we obtain the relation between the electron field and the Bloch--Nordsieck
field with four-loop accuracy.Comment: 20 pages. v2: ref. [48] added, small changes in the text, corresponds
to the journal versio
Light-by-light-type corrections to the muon anomalous magnetic moment at four-loop order
The numerically dominant QED contributions to the anomalous magnetic moment
of the muon stem from Feynman diagrams with internal electron loops. We
consider such corrections and present a calculation of the four-loop
light-by-light-type corrections where the external photon couples to a closed
electron or muon loop. We perform an asymptotic expansion in the ratio of
electron and muon mass and reduce the resulting integrals to master integrals
which we evaluate using analytical and numerical methods. We confirm the
results present in the literature which are based on different computational
methods.Comment: 16 page
Four-loop wave function renormalization in QCD and QED
We compute the on-shell wave function renormalization constant to four-loop order in QCD and present numerical results for all coefficients of the SU(Nc) color factors. We extract the four-loop Heavy Quark Effective Theory anomalous dimension of the heavy-quark field and also discuss the application of our result to QED
Four-loop wave function renormalization in QCD and QED
We compute the on-shell wave function renormalization constant to four-loop
order in QCD and present numerical results for all coefficients of the
SU colour factors. We extract the four-loop HQET anomalous dimension of
the heavy quark field and also discuss the application of our result to QED.Comment: 24 page
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