
Physics Letters B 762 (2016) 151–156
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Four-loop strong coupling beta-function in the Standard Model
A.V. Bednyakov
a
, A.F. Pikelner
b,∗,1
a
Joint Institute for Nuclear Research, 141980 Dubna, Russia
b
II. Institut für Theoretische Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
a r t i c l e i n f o a b s t r a c t
Article history:
Received
11 July 2016
Received
in revised form 1 September 2016
Accepted
6 September 2016
Available
online 13 September 2016
Editor:
A. Ringwald
Keywords:
Standard
Model
High-order
corrections
Renormalization
group
In this letter we present our results for the four-loop beta-function of the strong coupling in the Standard
Model of fundamental interactions. The expression is obtained from gluon self-energy diagrams in the
background field gauge without application of special infra-red rearrangement tricks. We take top-Yukawa
and self-Higgs interactions into account, but neglect electroweak gauge couplings. Ambiguities due to γ
5
treatment are discussed and a particular “reading” prescription for odd Dirac traces is advocated.
© 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP
3
.
Most of viable models describing Nature at high energies are
based on gauge symmetries. Quantum chromodynamics (QCD) is a
gauge theory of strong interactions and it is important to study its
strength described by the coupling α
s
both in the low- and high-
energy
limit. At low energies the QCD interactions play a dominant
role in binding quarks and gluons together into nucleons. At larger
scales the coupling α
s
decreases [1,2] due to non-Abelian nature of
the underlying gauge theory. Nevertheless, the precise value of α
s
is of paramount importance both for modern and future colliders
and for theoretical studies of physics going beyond the Standard
Model (SM) of fundamental interactions.
The
renormalization group equations (RGE) relate couplings at
different scales. By solving them one can not only confront mea-
surements
carried out at different energies with theory but also
study asymptotic behavior of the latter at scales inaccessible in
current and even future experiments.
The progress in calculation of beta-functions — key RGE quanti-
ties
— is tightly connected to the introduction of dimensional regu-
larization
[3] and (modified) minimal subtraction (or MS) scheme.
The former does not break gauge symmetry in d = 4 − 2 dimen-
sions
and the advantage of the latter lies in the fact that beta-
functions
are extracted only from ultraviolet (UV) asymptotics of
Feynman integrals. This fact allows one to drastically simplify a
*
Corresponding author.
E-mail
addresses: bednya@theor.jinr.ru (A.V. Bednyakov), pikelner@theor.jinr.ru
(A.F. Pikelner).
1
On leave of absence from Joint Institute for Nuclear Research, 141980 Dubna,
Russia.
calculation by modifying the infra-red (IR) structure of the consid-
ered
integrals by means of the so-called infra-red rearrangement
(IRR) procedure [4].
Pure
QCD results for the strong coupling beta-function are
known for quite a long time up to four loops [1,2,5–11]. The
four-loop results are obtained with the help of IRR procedure
leading to four-loop vacuum diagrams with all lines having the
same mass. The beta-function is extracted from the quark–gluon
[10] and ghost-gluon [11] vertex renormalization constants and
the corresponding wave function renormalization constants. Inde-
pendently,
the ghost field renormalization constant and the ghost-
gluon
vertex renormalization constant were calculated in Ref. [12].
The quark field renormalization constant [13] was found by a dif-
ferent
method bringing the problem to the calculation of three-
loop
massless propagator-type diagrams.
It
is obvious that in a precise study of QCD processes at high
energies one should consider other SM interactions and their effect
on the running of α
s
. Recently, the full set of three-loop beta-
functions
for all SM parameters, including the strong coupling, was
found in a series of papers [14–20].
In
this letter we present our result for the dominant four-loop
contribution to the beta-function of the strong coupling in the SM.
In our calculation we neglect the electroweak gauge interactions,
but keep top-Yukawa and Higgs self-interactions along with the
well-known QCD corrections. The calculation is carried out in the
background-field gauge (BFG) [21,22]. The advantage of BFG lies in
the QED-like relation between the gauge coupling renormalization
constant Z
a
s
and that of the background gluon field Z
ˆ
V
3
:
http://dx.doi.org/10.1016/j.physletb.2016.09.007
0370-2693/
© 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by
SCOAP
3
.