REVIEW
Three loop anomalous dimension of non-singlet quark currents in the RI' scheme
High Energy Physics - Phenomenology · Submitted 11 Apr 2003 · 37 references
Pith's verdict: A careful, well-checked three-loop RI' renormalization with a genuinely new tensor-current anomalous dimension; the only real soft spot is that the tensor finite parts have no external anchor.
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Referee report
The paper
The paper claims
Renormalizing QCD in the RI' scheme at three loops gives lattice practitioners the conversion factors that turn simulated tensor-current and quark-mass matrix elements into MS-bar numbers.
The reading
What carries the argument
The load-bearing construction is the RI' scheme definition itself: the renormalized quark two-point function is set equal to $p/$, the ghost two-point function to $1/p^2$, and the transverse and longitudinal parts of the gluon polarization to unity, all at $p^2 = mu^2$, with only the finite part absorbed; the coupling renormalization is deliberately kept MS-like, subtracting only poles and $ln(4 pi e^{-gamma})$, so that the Slavnov-Taylor identities survive. The anomalous dimensions of composite operators are then read off from $Z^{RI'}_{psi} Z^{RI'}_{O} langle psi(p) O(0) bar{psi}(-p) rangle = 1$ at $p^2 = mu^2$, with the Green's function decomposed into the two allowed Lorentz structures and projected out. Three-loop massless two-point integrals are evaluated with standard symbolic tools, and the scheme conversion functions $C_i = Z^{RI'}_i / Z^{MS}_i$, together with the derived relation between the RI' and MS-bar gauge parameters, convert MS-bar anomalous dimensions into RI' ones and provide the independent cross-check on every result.
Extended reading notes
Core claim
The paper establishes that QCD can be consistently renormalized at three loops in the RI' scheme in an arbitrary covariant gauge, with the coupling-constant renormalization coming out the same from the quark-gluon and ghost-gluon three-point functions, and that the resulting beta function agrees with the MS-bar one to the order where a difference could first appear, which pushes the agreement to four loops. On that foundation the author computes the RI' anomalous dimensions of the scalar, vector and tensor flavour non-singlet quark currents at three loops from the insertion of the operator at zero momentum in a massless quark two-point function. The scalar case reproduces the quark-mass anomalous dimension, confirming that the operator method matches the older massive-propagator route, and the tensor case, corresponding to the lowest moment of the transversity operator, gives a new gauge-dependent renormalization constant and anomalous dimension. Combining the two- and three-loop conversion functions with the known four-loop MS-bar mass anomalous dimension then yields the four-loop RI' mass anomalous dimension for arbitrary gauge parameter and any Lie group, and the vector current is shown to stay unrenormalized, as a conserved current should.
Load-bearing premise
The load-bearing premise is that the RI' scheme is the one fixed by this paper's own two-point-function conditions together with an MS-style coupling renormalization; the author states that a widely used earlier definition differs from it whenever the gauge parameter is non-zero and agrees only in Landau gauge, so away from Landau gauge these conversion factors belong to a different scheme than the earlier ones.
Editorial extensions
If this is right
- Lattice groups gain three-loop conversion factors for the tensor current, so transversity matrix elements can be matched to MS-bar with the same precision already available for quark masses.
- The four-loop RI' mass anomalous dimension, valid for any gauge parameter and any colour group, extends the earlier Landau-gauge-only conversion to non-zero gauge fixing.
- Because the three-loop RI' beta function equals the MS-bar one, the four-loop RI' beta function is also equal to the MS-bar result, so coupling-constant running needs no separate conversion.
- The same zero-momentum operator-insertion method can be applied directly to the twist-2 Wilson operators whose moments appear in the operator product expansion for deep inelastic scattering.
- The explicit three-loop relation between the RI' and MS-bar gauge parameters gives a reusable dictionary for any future RI' calculation performed away from Landau gauge.
Reading between the lines
- The paper's insistence that the RI' coupling be renormalized MS-like, rather than by absorbing finite vertex pieces, is a design choice that keeps Slavnov-Taylor identities intact; a reader could reasonably expect that choice to become the standard, since otherwise the scheme cannot be defined consistently beyond two-point functions.
- Because the vector current is protected, its finite Green's function doubles as a free consistency check on any future RI' operator calculation, and the author effectively uses it that way.
- The gauge-parameter conversion relation is itself a substantial by-product: any RI' result quoted at non-zero $alpha$ can be translated, so non-Landau-gauge lattice simulations become usable for matching rather than being discarded.
- Extending the method to operators with gluonic content would require the gluon and ghost field renormalizations computed here, which the author explicitly prepares for but does not use.
Original abstract
We renormalize QCD at three loops in the modified regularization invariant, RI', scheme in arbitrary covariant gauge and deduce that the four loop beta-function is equivalent to the MSbar result. The anomalous dimensions of the scalar, vector and tensor currents are then determined in the RI' scheme at three loops by considering the insertion of the operator in a quark two-point function. The expression for the scalar current agrees with the quark mass anomalous dimension and we deduce an expression for the four loop RI' mass anomalous dimension in arbitrary covariant gauge and for any Lie group.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We renormalize QCD at three loops in the modified regularization invariant, RI', scheme in arbitrary covariant gauge and deduce that the four loop beta-function is equivalent to the MSbar result. The anomalous dimensions of the scalar, vector and tensor currents are then determined in the RI' scheme at three loops by considering the insertion of the operator in a quark two-point function. The expression for the scalar current agrees with the quark mass anomalous dimension and we deduce an expression for the four loop RI' mass anomalous dimension in arbitrary covariant gauge and for any Lie group.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We renormalize QCD at three loops in the modified regularization invariant, RI', scheme in arbitrary covariant gauge and deduce that the four loop beta-function is equivalent to the MSbar result. | contribution 0.59 | 0.94 | 0.37 | asserted 1.00 |
| s1 | The anomalous dimensions of the scalar, vector and tensor currents are then determined in the RI' scheme at three loops by considering the insertion of the operator in a quark two-point function. | contribution 0.48 | 0.93 | 0.20 | asserted 1.00 |
| s2 | The expression for the scalar current agrees with the quark mass anomalous dimension and we deduce an expression for the four loop RI' mass anomalous dimension in arbitrary covariant gauge and for any Lie group. | result 0.97 | 0.94 | 0.25 | asserted 1.00 |
What was examined, and what was not
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References
How the literature uses it
49 arXiv papers cite this in 77 sentences
Papers citing it · 45 sentences without a confident label
Contests it 1 paper
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We agree with the moments given in [ref] and note a typo in the 15$^th$ moment of [ref] .
The 3-Loop Non-Singlet Heavy Flavor Contributions and Anomalous Dimensions for the Structure Function $F_2(x,Q^2)$ and Transversity · Transversity · contest 0.88
Uses its method or tool 9 papers
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This is then converted to the $MS$ scheme using continuum perturbation theory [ref] and evolved to a scale of 2 GeV that allows comparison with phenomenological estimates.
The nucleon isovector tensor charge from lattice QCD using chiral fermions · Renormalization · 0.94
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For the exceptional kinematic configuration we use the projectors of [ref] and the perturbative running and matching calculated in [ref] for mass and [ref] for the tensor current.
Step Scaling with off-shell renormalisation · Vertex functions with twisted boundary conditions at a single lattice spacing · 0.93
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Since lattice perturbation theory is slowly convergent and high-loop results are unavailable, we first match the local lattice QCD operators of interest non-perturbatively to the regulator independent RI'-MOM scheme [ref] and subsequently translate the result at three-loop order [ref] to the $MS$ scheme.
Magnetic susceptibility of QCD matter and its decomposition from the lattice · Multiplicative QCD renormalization · 1.00
Uses its data or values 7 papers
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In deriving the conversion factors via Eqs.([ref], [ref]), we take NLO coefficients of $C_q^→MS$ and $C_q^γ_μ→MS$ from [ref] and the NNLO coefficients from [ref] (setting $C_A=N_c$, $T_F=1/2$), [ref] (setting $w=1$, $r=1$) and [ref] .
RI-(S)MOM to $\overline{\rm MS}$ conversion for $B_K$ at two-loop order · $C_B_K^(S)MOM→MS$ up to NNLO · 0.98
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Restricting ourselves in these proceedings to two-loop order in Landau gauge and to quenched approximation (compare e.g. [ref] ), we have [equation] The coefficient $z^RI'_1,0=13.8257$ has been calculated in [ref] , a first rough estimate of $z^RI'_2,0$ has been presented by us at Lattice08 [ref] .
The lattice ghost propagator in Landau gauge up to three loops using Numerical Stochastic Perturbation Theory · The ghost propagator in standard LPT · 0.88
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From Ref. [ref] we get for $^S$ and $^P$ [equation] With the help of Ref. [ref] we find for $^T_μν$ [equation] For the vector and axial-vector currents $^V_μ$ and $^A_μ$ one finds from Ref. [ref] [equation] with $R = p_μ^2/p^2$.
Perturbative and Nonperturbative Renormalization in Lattice QCD · Results from continuum perturbation theory · 0.99
Compares with it 7 papers
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They are compared to the results in Refs. [ref] and are obtained in a first independent calculation for $γ_qg(N)$, $γ_qq^PS(N)$, $γ_qq^NS,TR(N)$, in Section [ref].
The O(\alpha_s^3) Massive Operator Matrix Elements of O(n_f) for the Structure Function F_2(x,Q^2) and Transversity · Introduction · 1.00
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All results agree with the foregoing literature [ref] .
Higher Order Heavy Quark Corrections to Deep-Inelastic Scattering · 3-Loop anomalous dimensions · 1.00
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We agree with the results given in [ref] and confirm the $T_F$-contributions for the moments $N=1$ to 8 given in Refs. [ref] .
2- and 3-Loop Heavy Flavor Corrections to Transversity · Anomalous Dimensions · 1.00
Cites it as background 3 papers
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It was also shown that the former is equivalent to the $$ scheme and is thus known to three-loop order [ref] , whereas the latter is known to two-loop order [ref] .
Matching factors for Delta S=1 four-quark operators in RI/SMOM schemes · Introduction · 0.83
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The corresponding perturbative calculation is relatively simple and those for the quark bilinear currents with all 16 gamma matrices have been obtained at 3 loops or more [ref] .
RI/MOM and RI/SMOM renormalization of quark bilinear operators using overlap fermions · Introduction · 0.96
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The anomalous dimensions for transversity are known to NLO [ref] and for a series of moments to 3–loop order [ref] .
The O(\alpha_s^3) Massive Operator Matrix Elements of O(n_f) for the Structure Function F_2(x,Q^2) and Transversity · The Operator Matrix Elements for Transversity · 0.94
Discussion
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