arXiv subjects

Marco Niggetiedt

Publications and source records attributed to Marco Niggetiedt.

12 recordsLinked to original sources

arXiv2026

Three-loop QCD+QED corrections to on-shell quark renormalization

We present the three-loop QCD+QED mixed corrections to the on-shell quark mass and wave-function renormalization constants through orders $\mathcal{O}(α_s^mα^n)$ with $m+n=3$. We further derive the three-loop relation between the pole mass and the $\overline{\text{MS}}$ mass of a heavy quark, including the complete mixed QCD+QED contributions. The corresponding quark-mass anomalous dimension in the presence of both interactions is also extracted. Moreover, we provide the explicit conversion formulae, up to the same perturbative order, between the pole mass and the trace-anomaly subtracted $σ$-mass of heavy quark.

hep-ph↗

arXiv2025

Three-loop QCD Mass Relation between the $\overline{\mathrm{MS}}$ and Symmetric-momentum Subtraction Scheme Away from the Chiral Limit

The perturbative result for the quark-mass conversion factor between the $\overline{\mathrm{MS}}$ and regularization-independent symmetric-momentum subtraction scheme (RI/SMOM) away from the chiral limit, i.e. at non-zero quark masses (RI/mSMOM), is derived up to three loops in QCD, extending the existing result by two additional orders. We further explore an illuminating possibility that in Dimensional Regularization, the original RI/(m)SMOM renormalization conditions may be interpreted merely in a weaker sense, namely as equations holding just in the 4-dimensional limit rather than exactly in $d$ dimensions: they result in different, albeit simpler, renormalization constants but still the same finite conversion factor. This novel observation has the added benefit of reducing computational effort, particularly at high orders. Our high-order results for the conversion factor exhibit rich behaviors, and in particular a window is observed in the subtraction scale and mass where it receives less perturbative corrections than the RI/SMOM counterpart up to three loops; this finding may help to further improve the accuracy of $\overline{\mathrm{MS}}$ quark-mass determinations with Lattice QCD.

hep-ph↗

arXiv2025

On-shell Matrix Elements of the EMT Trace in Gauge Theories and Heavy Quark Masses

We present a novel diagrammatic proof of the identity between the forward matrix element of the energy-momentum-tensor (EMT) trace operator over a single particle's on-shell state and its perturbative pole mass to any loop orders in perturbative gauge theories (with gauge bosons and fermions), without appealing to any pre-laid operator renormalization conditions or Ward identities. The proof is based on the equation of mass-dimensional analysis in dimensional regularization, the topological properties of contributing Feynman diagrams and the on-shell renormalization condition. Considering for definiteness perturbative QED and QCD with at most one fermion kept massive, we have verified the aforementioned identity, up to three loops, for all elementary particles through direct computation of dimensionally-regularized matrix elements of the relevant bare operators. We observe interestingly that the trace-anomaly contribution seemingly contains all leading-renormalon effects (explicitly verified up to three loops), and we propose accordingly a new scheme- and scale-independent trace-anomaly-subtracted mass definition for heavy $t$-,$\,b$-,$\,c$-quarks and electrons. A list of amusing numbers is subsequently presented for the composition of their perturbative pole masses.

hep-ph↗

arXiv2025

Precision tests of third-generation four-quark operators: $gg \to h$ and $h \to γγ$

We compute the two-loop contributions to Higgs production via gluon-gluon fusion ($gg \to h$) and Higgs decay into two photons ($h \to γγ$), arising from third-generation four-quark operators in the Standard Model effective field theory (SMEFT). Our analysis is performed in the broken phase of the theory, retaining the full dependence on the Higgs and heavy-quark masses. This includes both finite matching corrections and logarithmic effects stemming from the renormalization group evolution within the SMEFT. As a byproduct, new two-loop anomalous dimensions in the SMEFT are obtained. We also briefly discuss the phenomenological implications of our two-loop calculations.

hep-ph↗

arXiv2024

Renormalization of the pseudoscalar operator at four loops in QCD

We present the renormalization constant of the pseudoscalar operator defined with a non-anticommuting $γ_5$ in dimensional regularization up to four-loop order in perturbative Quantum Chromodynamics (QCD). Furthermore, by virtue of renormalization-group invariance of the relation between the scalar and the pseudoscalar operator, we predict the $\overline{\mathrm{MS}}$ factor of the renormalization constant for the latter at five-loop order in QCD.

hep-ph↗

arXiv2024

Quark Mass Effects in Higgs Production

We examine the effect of finite top- and bottom-quark masses on the Higgs production cross section in the gluon-gluon fusion channel. We employ both $\overline{\text{MS}}$ and on-shell renormalisation for the quark masses and provide a thorough comparison. Furthermore, we explore alternative treatments of quark masses, in particular in the four-flavour scheme, and investigate their impact on the cross section. Our work also presents novel predictions for differential cross sections in the Higgs rapidity. The results lead to a significant reduction of scale uncertainties, and our analysis enables us to offer well-grounded recommendations for future research in this area.

hep-ph↗

arXiv2024

Exact two-loop amplitudes for Higgs plus jet production with a cubic Higgs self-coupling

We compute the corrections to the two-loop amplitudes for $gg \to h$, $gg \to hg$, $qg \to hq$, and $q \bar q \to hg$ due to a modified cubic Higgs self-coupling. The exact dependence on the Higgs and top-quark masses across the entire $2 \to 2$ phase space is determined by numerically solving a system of differential equations for the relevant master integrals. The calculated amplitudes are crucial for evaluating the impact of the considered corrections on exclusive $pp \to hj$ production at the hadronic event level. As an application, we calculate the non-universal, kinematic-dependent cubic Higgs self-coupling corrections to the Higgs-boson transverse momentum distribution in gluon-gluon fusion Higgs production for arbitrary values of the transverse momentum.

hep-ph↗

arXiv2024

Higgs-boson production in the full theory at NNLO+PS

We consider the production of a Standard-Model (SM) Higgs boson in gluon fusion in hadronic collisions and compute the QCD corrections up to next-to-next-to-leading order (NNLO) and match them to parton showers (NNLO+PS). The complete dependence on the top-quark mass is taken into account without making any approximations to the top quark loops mediating the coupling between the gluons and the Higgs boson. To this end, we have included the $gg\to H$ amplitudes up to three loops and the $pp\to H$+jet amplitudes up to two loops in the full SM theory. This is the first fully differential calculation of the top-quark mass effects up to NNLO in QCD, and we study their impact on relevant observables for the LHC.

hep-ph↗

arXiv2024

Top-Bottom Interference Contribution to Fully-Inclusive Higgs Production

We evaluate the top-bottom interference contribution to the fully-inclusive Higgs production cross section at next-to-next-to-leading order in QCD. Although bottom-quark-mass effects are power-suppressed, the accuracy of state-of-the-art theory predictions makes an exact determination of this effect indispensable. The total effect of the interference at 13 TeV is $-1.99(1)^{+0.30}_{-0.15}$ pb, while the pure $\mathcal{O}(α_s^4)$ correction is 0.43 pb. With this result, we address one of the leading theory uncertainties of the cross section.

hep-ph↗

arXiv2024

The Higgs-gluon form factor at three loops in QCD with three mass scales

We report on the complete three-loop corrections to the Higgs-gluon form factor in QCD. While previous calculations are based on QCD with a single heavy quark of arbitrary mass, we extend the study to QCD involving two different massive quark flavors. Thereby, the full set of possible Feynman diagrams at three-loop order is taken into account. Employing differential equations for the relevant master integrals, we determine the form factor in terms of analytic expansions. Outside the radii of convergence, we compute high-precision numerical samples over the two-dimensional physical parameter space. Our new findings will enter as virtual corrections the computation of the top-bottom interference in hadronic Higgs-boson production at next-to-next-to-leading order (NNLO) in QCD.

hep-ph↗

arXiv2021

The complete singlet contribution to the massless quark form factor at three loops in QCD

It is well known that the effect of top quark loop corrections in the axial part of quark form factors (FF) does not decouple in the large top mass or low energy limit due to the presence of the axial-anomaly type diagrams. The top-loop induced singlet-type contribution should be included in addition to the purely massless result for quark FFs when applied to physics in the low energy region, both for the non-decoupling mass logarithms and for an appropriate renormalization scale dependence. In this work, we have numerically computed the so-called singlet contribution to quark FFs with the exact top quark mass dependence over the full kinematic range. We discuss in detail the renormalization formulae of the individual subsets of the singlet contribution to an axial quark FF with a particular flavor, as well as the renormalization group equations that govern their individual scale dependence. Finally we have extracted the 3-loop Wilson coefficient in the low energy effective Lagrangian, renormalized in a non-$\overline{\mathrm{MS}}$ scheme and constructed to encode the leading large mass approximation of our exact results for singlet quark FFs. We have also examined the accuracy of the approximation in the low energy region.

hep-ph↗

arXiv2021

Exact quark-mass dependence of the Higgs-photon form factor at three loops in QCD

We follow up on our discussion of the exact quark-mass dependence of the Higgs-gluon form factor at three loops in QCD (arXiv:2001.03008) and turn our attention to the closely related Higgs-photon form factor. Similarly to our previous work, we intend to examine the form factor for the decay of a Higgs-boson with variable mass into two photons at the three-loop level in QCD. The set of master integrals is known numerically due to prior work on the Higgs-gluon form factor and is exploited to obtain expansions around the threshold as well as in the high-energy limit. Our results may be utilised to derive the photonic decay rate of the Higgs-boson through next-to-next-to-leading order.

hep-ph↗