arXiv subjects

R. V. Harlander

Publications and source records attributed to R. V. Harlander.

15 recordsLinked to original sources

arXiv2025

Two-loop gradient-flow renormalization of scalar QCD

The gradient-flow formalism is applied to a non-Abelian gauge theory with scalar and fermionic particles, dubbed "scalar QCD". It is shown that the flowed scalar quark requires a field renormalization, albeit only beyond the one-loop level. A pseudo-physical, t-dependent renormalization scheme is defined, and the corresponding renormalization constant is evaluated at the two-loop level. We also calculate the gluon action density as well as the condensate of the scalar and the fermionic quark at three-loop level in this theory. The results validate the consistency of the gradient-flow formalism in this theory and provide a further step towards applying the gradient-flow formalism to the full Standard Model.

hep-ph↗

arXiv2025

FeynGame 3.0

A major update of the program FeynGame is introduced. One of its main new functionalities is to visualize Feynman graphs generated by QGRAF. The QGRAF output can be either pasted into the FeynGame canvas for individual graphs, or the whole QGRAF output file can be processed. In addition, a number of new features and improvements have been implemented into FeynGame-3.0 in order to further facilitate the efficient drawing of Feynman diagrams in publication quality. FeynGame is freely available as jar or MacOS app file from https://web.physik.rwth-aachen.de/user/harlander/software/feyngame, and as source code from https://gitlab.com/feyngame/FeynGame.

hep-ph↗

arXiv2023

Standard Model Effective Field Theory up to Mass Dimension 12

We present a complete and non-redundant basis of effective operators for the Standard Model Effective Field Theory up to mass dimension 12 with three generations of fermions. We also include operators coupling to gravity via the Weyl tensor. The results are obtained by implementing the algorithm of Li et al., and provided in the form of ancillary files.

hep-ph↗

arXiv2023

Exact top-quark mass dependence in hadronic Higgs production

The impact of the finite top-quark mass on the inclusive Higgs production cross section at higher perturbative orders has been an open question for almost three decades. In this paper, we report on the computation of this effect at NNLO QCD. For the purely gluonic channel, it amounts to $+0.62\%$ relative to the result obtained in the HEFT approximation. The formally sub-leading partonic channels over-compensate this shift, leading to an overall effect of $-0.32\%$ at a $pp$ collider energy of $13\,\mathrm{TeV}$, and $-0.16\%$ at $8\,\mathrm{TeV}$. This result eliminates one of the main theoretical uncertainties to inclusive Higgs production cross section at the LHC.

hep-ph↗

arXiv2020

The light CP-even MSSM Higgs mass including N$^3$LO+N$^3$LL QCD corrections

We present a calculation of the light neutral CP-even Higgs boson pole mass in the real MSSM which combines state-of-the-art EFT and fixed-order results, including the three-loop fixed-order QCD corrections as well as the resummation of logarithmic terms in the ratio of the weak to the SUSY scale up to fourth logarithmic order. This hybrid calculation should be valid for arbitrary SUSY scales above the weak scale. Comparison to the pure fixed-order and EFT results provides an estimate of their individual validity range.

hep-ph↗

arXiv2020

FeynGame

A java-based graphical tool for drawing Feynman diagrams is presented. It differs from similar existing tools in various respects. For example, it is based on models, consisting of particles (lines) and (optionally) vertices, each of which can be given their individual properties (line style, color, arrows, label, etc.). The diagrams can be exported in any standard image format, or as PDF. Aside from its plain graphical aspect, the goal of FeynGame is also educative, as it can check a Feynman diagrams validity. This provides the basis to play games with diagrams, for example. Here we describe on such game where a given set of initial and final states must be connected through a Feynman diagram within a given interaction model.

physics.ed-ph↗

arXiv2019

The light CP-even MSSM Higgs mass resummed to fourth logarithmic order

We present the calculation of the light neutral CP-even Higgs mass in the MSSM for a heavy SUSY spectrum by resumming enhanced terms through fourth logarithmic order (N$^3$LL), keeping terms of leading order in the top Yukawa coupling $α_t$, and NNLO in the strong coupling $α_s$. To this goal, the three-loop matching coefficient for the quartic Higgs coupling of the SM to the MSSM is derived to order $α_t^2α_s^2$ by comparing the perturbative EFT to the fixed-order expression for the Higgs mass. The new matching coefficient is made available through an updated version of the program Himalaya. Numerical effects of the higher-order resummation are studied using specific examples, and sources of theoretical uncertainty on this result are discussed.

hep-ph↗

arXiv2018

Exploiting the WH/ZH symmetry in the search for New Physics

We suggest to isolate the loop-induced gluon-initiated component ($gg\to ZH$) for associated $ZH$ production by using the similarity of the Drell-Yan-like component for $ZH$ production to the $WH$ process. We argue that the cross-section ratio of the latter two processes can be predicted with high theoretical accuracy. Comparing it to the experimental $ZH/WH$ cross-section ratio should allow to probe for New Physics in the $gg\to ZH$ component at the HL-LHC. We consider typical BSM scenarios in order to exemplify the effect they would have on the proposed observable.

hep-ph↗

arXiv2014

Towards precise predictions for Higgs-boson production in the MSSM

We study the production of scalar and pseudoscalar Higgs bosons via gluon fusion and bottom-quark annihilation in the MSSM. Relying on the NNLO-QCD calculation implemented in the public code SusHi, we provide precise predictions for the Higgs-production cross section in six benchmark scenarios compatible with the LHC searches. We also provide a detailed discussion of the sources of theoretical uncertainty in our calculation. We examine the dependence of the cross section on the renormalization and factorization scales, on the precise definition of the Higgs-bottom coupling and on the choice of PDFs, as well as the uncertainties associated to our incomplete knowledge of the SUSY contributions through NNLO. In particular, a potentially large uncertainty originates from uncomputed higher-order QCD corrections to the bottom-quark contributions to gluon fusion.

hep-ph↗

arXiv2010

Light MSSM Higgs boson mass to three-loop accuracy

The light CP even Higgs boson mass, Mh, is calculated to three-loop accuracy within the Minimal Supersymmetric Standard Model (MSSM). The result is expressed in terms of DRbar parameters and implemented in the computer program H3m. The calculation is based on the proper approximations and their combination in various regions of the parameter space. The three-loop effects to Mh are typically of the order of a few hundred MeV and opposite in sign to the two-loop corrections. The remaining theory uncertainty due to higher order perturbative corrections is estimated to be less than 1 GeV.

hep-ph↗

arXiv2008

Higgs boson mass in supersymmetry to three loops

Within the minimal supersymmetric extension of the Standard Model, the mass of the light CP-even Higgs boson is computed to three-loop accuracy, taking into account the next-to-next-to-leading order effects from supersymmetric Quantum Chromodynamics. We consider two different scenarios for the mass hierarchies of the supersymmetric spectrum. Our numerical results amount to corrections of about 500 MeV which is of the same order as the experimental accuracy expected at the CERN Large Hadron Collider (LHC).

hep-ph↗

arXiv2007

Running of $α_s$ and $m_b$ in the MSSM

A consistent evolution of the strong coupling constant $α_s$ from $M_Z$ to the GUT scale is presented, involving three-loop running and two-loop decoupling. The two-loop transition from the MS- to the DR-scheme is properly taken into account. In the second part of the paper, the bottom quark mass in the DR-scheme at the electroweak/SUSY scale is evaluated with four-loop accuracy. We find that the three-loop effects are comparable to the experimental uncertainty both for $α_s$ and $m_b$.

hep-ph↗

arXiv2007

Four-loop beta function and mass anomalous dimension in Dimensional Reduction

Within the framework of QCD we compute renormalization constants for the strong coupling and the quark masses to four-loop order. We apply the DR-bar scheme and put special emphasis on the additional couplings which have to be taken into account. This concerns the epsilon-scalar--quark Yukawa coupling as well as the vertex containing four epsilon-scalars. For a supersymmetric Yang Mills theory, we find, in contrast to a previous claim, that the evanescent Yukawa coupling equals the strong coupling constant through three loops as required by supersymmetry.

hep-ph↗

arXiv2002

Quartic mass corrections to R_had at order α_s^3

The total cross section for the production of massive quarks in electron positron annihilation can be predicted in perturbative QCD. After expansion in m^2/s the quartic terms, i.e. those proportional to m^4/s^2, are calculated up to order α_s^3 for vector and axial current induced rates. Predictions relevant for charm, bottom and top quarks production are presented. The α_s^3 corrections are shown to be comparable to terms of order α_s and α_s^2. As a consequence, the predictions exhibit a sizeable dependence on the renormalization scale. The stability of the prediction is improved and, at the same time, the relative size of the large order terms decreases by replacing the running mass \bar{m}(μ) with the scheme independent invariant one \hat{m}. By combining these results with the prediction for massless case and the quadratic mass terms the cross section for massive quark production at electron positron colliders is put under control in order α_s^3 from the high energy region down to fairly low energies.

hep-ph↗

arXiv2002

Summary: Working Group on QCD and Strong Interactions

In this summary of the considerations of the QCD working group at Snowmass 2001, the roles of quantum chromodynamics in the Standard Model and in the search for new physics are reviewed, with empahsis on frontier areas in the field. We discuss the importance of, and prospects for, precision QCD in perturbative and lattice calculations. We describe new ideas in the analysis of parton distribution functions and jet structure, and review progress in small-$x$ and in polarization.

hep-ph↗