arXiv subjects

Sven-Olaf Moch

Publications and source records attributed to Sven-Olaf Moch.

At least 37 records · Page 2Linked to original sources

arXiv2025

NNLO QCD$\otimes$QED corrections to unpolarized and polarized SIDIS

We present the first computation of next-to-next-to-leading order (NNLO) pure QED and mixed QCD$\otimes$QED corrections to unpolarized and polarized semi-inclusive deep-inelastic scattering (SIDIS). Building on our previous NNLO QCD results, these corrections are crucial for improving the theoretical precision. The coefficient functions are derived within the QCD factorization framework using dimensional regularization, with consistent renormalization and mass factorization. A detailed phenomenological analysis shows that the NNLO QED and QCD$\otimes$QED terms enhance perturbative stability and reduce scale uncertainties. These results are essential for high-precision SIDIS predictions at future facilities such as the Electron-Ion Collider.

hep-ph↗

arXiv2025

Soft and virtual corrections to semi-inclusive DIS up to four loops in QCD

We apply the threshold resummation formalism for semi-inclusive deep-inelastic scattering (SIDIS) to derive the soft and virtual corrections for the SIDIS cross section up to four loops in QCD. Using the recently computed next-to-next-to-leading order QCD corrections for the SIDIS cross section together with known results for the form factor and splitting functions in QCD up to four loops, we derive the complete soft and collinear contributions to the SIDIS coefficient functions at four-loop order. We also include systematically the next-to-leading power corrections, which are suppressed near threshold. The numerical analysis of the new four-loop corrections shows a small effect on the cross section underpinning the very good perturbative stability of the SIDIS process at that order in perturbation theory, including the reduced dependence on the renormalization and factorization scales $μ_R$ and $μ_F$.

hep-ph↗

arXiv2025

NNLO phase-space integrals for semi-inclusive deep-inelastic scattering

We evaluate the phase-space integrals that arise in double real emission diagrams for semi-inclusive deep-inelastic scattering at next-to-next-to-leading order (NNLO) in QCD. Utilizing the reverse unitarity technique, we convert these integrals into loop integrals, allowing us to employ integration-by-parts identities and reduce them to a set of master integrals. The master integrals are then solved using the method of differential equations and expressed in terms of Goncharov polylogarithms. By examining the series expansion in the dimensional regulator, we discover additional relations among some of the master integrals. As an alternative approach, we solve the master integrals by decomposing them into angular and radial components. The angular parts are evaluated using Mellin-Barnes representation, while special attention is given to the singular structures of the radial integrals to handle them accurately. Here the results are provided in terms of one-fold integrals over classical polylogarithms. This approach provides a clearer understanding of the origin of soft and collinear singularities.

hep-ph↗

arXiv2024

Exploring SMEFT Couplings Using the Forward-Backward Asymmetry in Neutral Current Drell-Yan Production at the LHC

Neutral current Drell-Yan (DY) lepton-pair production is considered in the framework of the Standard Model Effective Field Theory (SMEFT). Using the open-source fit platform xFitter, we investigate the impact of high-statistics measurements of the neutral current DY (NCDY) forward-backward asymmetry $A_{\rm{FB}}$ near the weak boson mass scale in the present and forthcoming stages of the Large Hadron Collider (LHC). Besides recovering earlier results on the $A_{\rm{FB}}$ sensitivity to parton distribution functions, we analyze the precision determination of $Z$-boson couplings to left-handed and right-handed $u$-quarks and $d$-quarks, and explore Beyond-Standard-Model contributions using the SMEFT framework. We perform a sensitivity study and comment on the role of the $A_{\rm{FB}}$ asymmetry for the electroweak SMEFT fit and precision $Z$-boson physics at the LHC and high-luminosity HL-LHC.

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arXiv2024

LASS, the numerics

We summarize our efforts to create a numerical implementation of the Local Analytical Subtraction Scheme (LASS) for obtaining NNLO QCD predictions in electron-positron collisions. We focus on the regularization of double-real radiation contributions, which are typically the most computationally intensive part of NNLO calculations. We describe the structure of the subtraction terms in LASS and our approach to numerically validate them. Using arbitrary precision arithmetic, we demonstrate the proper convergence of individual subtraction terms, overlap removal terms, and spurious singularity cancellations in various singular limits. We show results for the specific case of three-jet production in $e^+e^-$ collisions. Our results validate the correctness of both the LASS formalism and our numerical implementation, setting the stage for full NNLO calculations using this method.

hep-ph↗

arXiv2024

Analysis of $(n+1)$ and $n$-parton contributions for computing QCD jet cross sections in the local analytic subtraction scheme

We analyze and implement the Local Analytic Sector Subtraction (LASS) scheme for handling infrared singularities in next-to-next-to-leading order (NNLO) calculations in perturbative QCD. We examine the key aspects of the scheme including sector function construction, singular limit parametrization, subtraction counterterm derivation, and integration techniques. As a proof-of-concept, we numerically implement LASS for the process $e^+e^- \rightarrow 3$ jets. In this study we examine the limiting behavior of subtraction terms for real-virtual contribution and explicitly demonstrate the pole cancellation of the double-virtual contribution. Differential cross sections are computed for several event shape observables, showing the stability and efficiency of LASS scheme. This work lays the foundation for developing an automated tool for NNLO QCD calculations using this promising scheme.

hep-ph↗

arXiv2024

On evolution kernels of twist-two operators

The evolution kernels that govern the scale dependence of the generalized parton distributions are invariant under transformations of the $\mathrm{SL}(2,\mathrm R)$ collinear subgroup of the conformal group. Beyond one loop the symmetry generators, due to quantum effects, differ from the canonical ones. We construct the transformation which brings the {\it full} symmetry generators back to their canonical form and show that the eigenvalues (anomalous dimensions) of the new, canonically invariant, evolution kernel coincide with the so-called parity respecting anomalous dimensions. We develop an efficient method that allows one to restore an invariant kernel from the corresponding anomalous dimensions. As an example, the explicit expressions for NNLO invariant kernels for the twist two flavor-nonsinglet operators in QCD and for the planar part of the universal anomalous dimension in $ N=4$ SYM are presented.

hep-ph↗

arXiv2024

NNLO QCD corrections to semi-inclusive DIS

We present the first results for the next-to-next-to leading order (NNLO) corrections to the semi-inclusive deep-inelastic scattering process in perturbative quantum chromodynamics. We consider the quark initiated flavor non-singlet process and obtain the complete contributions analytically at leading color. All relevant virtual and real emission Feynman diagrams have been computed using integration-by-parts reduction to master integrals and two approaches for their subsequent evaluation (parametric phase-space integration and method of differential equations). The numerical analysis demonstrates the significance of the NNLO corrections and their great impact on the reduction of the residual scale dependence.

hep-ph↗

arXiv2023

Compatibility between theoretical predictions and experimental data for top-antitop hadroproduction at NNLO QCD accuracy

We compare double-differential normalized production cross sections for top-antitop $+ X$ hadroproduction at NNLO QCD accuracy, as obtained through a customized version of the MATRIX framework interfaced to PineAPPL, with recent data by the ATLAS and CMS collaborations. We take into account theory uncertainties due to scale variation and we see how predictions vary as a function of parton distribution function (PDF) choice and top-quark pole mass value, considering different state-of-the-art PDF fits with their uncertainties. Notwithstanding the overall reasonable good agreement, we observe discrepancies at the level of a few $σ$'s between data and theoretical predictions in some kinematical regions, which can be alleviated by refitting the top-quark mass value, and/or the PDFs and/or $α_s(M_Z)$, considering the correlations between these three quantities. In a fit of top-quark mass standalone, we notice that, for all considered PDF + $α_s(M_Z)$ sets used as input, some datasets point towards top-quark pole mass values lower by about $2\,σ$'s than those emerging from fitting other datasets, suggesting a possible tension between experimental measurements using different decay channels, and/or the need of better estimating uncertainties on the latter.

hep-ph↗

arXiv2023

Investigation of the scale dependence in the MSR and $\overline{\textrm{MS}}$ top quark mass schemes for the $\mathrm{t}\overline{\mathrm{t}}$ invariant mass differential cross section using LHC data

The computation of the single-differential top quark-antiquark pair ($\mathrm{t}\overline{\mathrm{t}}$) production cross section at NLO in the fixed-order expansion is examined consistently using the MSR and $\overline{\textrm{MS}}$ short-distance top quark mass schemes. A thorough investigation of the dependence of different regions of the $\mathrm{t}\overline{\mathrm{t}}$ invariant mass spectrum on the renormalization scales $R$ and $μ_m$ of the MSR mass $m_\mathrm{t}^{\textrm{MSR}}(R)$ and $\overline{\textrm{MS}}$ mass $\overline{m}_\mathrm{t}(μ_m)$, respectively, is carried out. We demonstrate that a scale choice of $R\sim 80$~GeV is important for the stability of the cross-section predictions for the low $\mathrm{t}\overline{\mathrm{t}}$ invariant mass range, which is important for a reliable extraction of the top quark mass. Furthermore, a choice of semi-dynamical renormalization and factorization scales is preferred. These findings are expected to remain valid once non-relativistic quasi-bound state effects are included in the low invariant mass region.

hep-ph↗

arXiv2023

Particle physics facing a pandemic

Our ordinary life changed quite a bit in March of 2020 due to the global Covid-19 pandemic. While spring time in general well awaited and regarded as a synonym for rejuvenation the spring of 2020 brought lock-down, curfew, home office and digital education to the lives of many. The particle physics community was not an exception: research institutes and universities introduced home office and digital lecturing and all workshops, conferences and summer schools were canceled, got postponed or took place online. Using publicly available data from the INSPIRE and arXiv databases we investigate the effects of this dramatic change of life to the publishing trends of the high-energy physics community with an emphasis on particle phenomenology and theory. To get insights we gather information about publishing trends in the last 20 years, and analyse it in detail.

physics.soc-ph↗

arXiv2022

Single-differential top quark pair production cross sections with running mass schemes at NLO

Single-differential cross section predictions for top quark pair production are presented at next-to-leading order, using running top quark mass renormalization schemes. The evolution of the mass of the top quark is performed in the MSR scheme $m_{\mathrm{t}}^{\textrm{MSR}}(μ)$ for renormalization scales $μ$ below the $\overline{\textrm{MS}}$ top quark mass $\overline{m}_{\mathrm{t}}(\overline{m}_{\mathrm{t}})$, and in the $\overline{\textrm{MS}}$ scheme $\overline{m}_{\mathrm{t}}(μ)$ for scales above. In particular, the implementation of a mass renormalization scale independent of the strong coupling renormalization scale and factorization scale in quantum chromodynamics allows investigating independent dynamical scale variations. Furthermore, the first theoretically consistent extraction of the top quark MSR mass from experimental data is presented.

hep-ph↗

arXiv2022

Anti-$k_T$ jet function at next-to-next-to-leading order

Jets constructed via clustering algorithms (e.g., anti-$k_T$, soft-drop) have been proposed for many precision measurements, such as the strong coupling $α_s$ and the nucleon intrinsic dynamics. However, the theoretical accuracy is affected by missing QCD corrections at higher orders for the jet functions in the associated factorization theorems. Their calculation is complicated by the jet clustering procedure. In this work, we propose a method to evaluate jet functions at higher orders in QCD. The calculation involves the phase space sector decomposition with suitable soft subtractions. As a concrete example, we present the quark-jet function using the anti-$k_T$ algorithm with E-scheme recombination at next-to-next-to-leading order.

hep-ph↗

arXiv2022

Report of the Topical Group on Top quark physics and heavy flavor production for Snowmass 2021

This report summarizes the work of the Energy Frontier Topical Group on EW Physics: Heavy flavor and top quark physics (EF03) of the 2021 Community Summer Study (Snowmass). It aims to highlight the physics potential of top-quark studies and heavy-flavor production processes (bottom and charm) at the HL-LHC and possible future hadron and lepton colliders and running scenarios.

hep-ph↗

arXiv2022

One-loop soft anomalous dimension matrices for $t\bar t j$ hadroproduction

We calculate the one-loop corrections to the soft anomalous dimension matrices for the production of a top-antitop quark pair in association with a jet at hadron colliders. This is a step forward towards implementing a procedure for the resummation of soft-gluon emission logarithms for the $t\bar{t}j + X$ hadroproduction process, that will enable the improvement of the accuracy of the $t\bar{t} j + X$ cross sections, beyond the current degree of knowledge. The latter, so far, has reached the next-to-leading order (NLO) level, complemented by the accuracy of the Shower Monte Carlo approaches used in matching the NLO computations to parton showers (PS) and by merging with matrix elements with a different number of light jets.

hep-ph↗

arXiv2022

Phenomenology of $t\bar{t}j + X$ production at the LHC

We present phenomenological results for $t\bar{t}j + X$ production at the Large Hadron Collider, of interest for designing forthcoming experimental analyses of this process. We focus on those cases where the $t\bar{t}j + X$ process is considered as a signal. We discuss present theoretical uncertainties and the dependence on relevant input parameters entering the computation. For the ${\cal R}$ distribution, which depends on the invariant mass of the $t\bar{t}j$-system, we present reference predictions in the on-shell, $\overline{\mbox{MS}}$ and MSR top-quark mass renormalization schemes, applying the latter scheme to this process for the first time. Our conclusions are particularly interesting for those analyses aiming at extracting the top-quark mass from cross-section measurements.

hep-ph↗

arXiv2022

Top-quark mass extraction from $t\bar{t}j +X$ events at the LHC: theory predictions

Past work has proven the possibility of extracting the top-quark mass, one of the fundamental parameters of the Standard Model, from the comparison of theory predictions and experimental measurements of differential cross-sections for $t\bar{t} j~+~X$ hadroproduction. Various experimental analyses in this respect have already been performed, and new ones are in preparation on the basis of the latest data from $pp$ collisions collected at the Large Hadron Collider. We have produced and made public a comprehensive set of theoretical predictions for the relevant differential distributions, ready to be used for presently ongoing and forthcoming experimental analyses. We investigate the role of different theoretical inputs, in particular the factorization and renormalization scales, PDFs and top-quark mass renormalization schemes, and we quantify the uncertainties related to different choices for these inputs, providing recommendations.

hep-ph↗

arXiv2022

Renormalization of non-singlet quark operator matrix elements for deep-inelastic scattering

We introduce a new method for calculating the mixing matrix for non-singlet quark operators including total derivatives, based solely on their renormalization structure in the chiral limit. As input, the method requires the well-known forward anomalous dimensions, which determine the evolution of parton distribution functions, and a calculation of the matrix elements of operators without total derivatives. Assuming a large number of quark flavors $n_f$, we are able to calculate the mixing matrix to fifth order in the strong coupling $α_s$ in the $\overline{\mbox{MS}}$-scheme.

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