Publications

Order by: publication date number of citations

• The Soft Anomalous Dimension at four loops in the Regge Limit

  Niamh Maher, Giulio Falcioni, Einan Gardi, Calum Milloy, Leonardo Vernazza

  SciPost Phys. Proc. 7, 013 (2022) · published 20 June 2022 | Toggle abstract · pdf

  The soft anomalous dimension governs the infrared divergences of scattering amplitudes in general kinematics to all orders in perturbation theory. By comparing the recent Regge-limit results for $2\to2$ scattering (through Next-to-Next-to-Leading Logarithms) in full colour to a general form for the soft anomalous dimension at four loops we derive powerful constraints on its kinematic dependence, opening the way for a bootstrap-based determination.

• On the modeling of $t\bar{t}W^\pm$ signatures at the LHC

  Manfred Kraus

  SciPost Phys. Proc. 7, 010 (2022) · published 20 June 2022 | Toggle abstract · pdf

  We discuss our recent progress on improving the theoretical description of the $pp\to t\bar{t}W^\pm$ process with particular focus on fiducial signatures that include top-quark decays. We employ a wide range of techniques from parton shower matching, narrow width approximation to full off-shell computations to assess the importance of the different modeling approaches.

• A pitfall in applying non-anticommuting $γ_5$ in $q\overline{q} \rightarrow ZH$ amplitudes

  Taushif Ahmed

  SciPost Phys. Proc. 7, 008 (2022) · published 20 June 2022 | Toggle abstract · pdf

  In computing the two-loop QCD corrections to a class of Feynman diagrams for the process $q\overline{q} \rightarrow ZH$ in Higgs effective field theory, we discover a striking phenomenon. We find the need for an additional local composite operator in the renormalised Lagrangian while employing a non-anticommuting $\gamma_5$ in dimensional regularisation. The computation using anticommuting $\gamma_5$, however, does not require any such amendment.

• NLO QCD corrections for off-shell $t\bar{t}b\bar{b}$

  Michele Lupattelli

  SciPost Phys. Proc. 7, 006 (2022) · published 20 June 2022 | Toggle abstract · pdf

  We present a full off-shell NLO QCD calculation of $pp \rightarrow e^+ \nu_e b \mu^- \bar{\nu}_\mu \bar{b} b \bar{b} + X$. Results are obtained using the \textsc{Helac-Nlo} Monte Carlo framework. We discuss a comparison to previous results and to experimental measurements. We also investigate the contribution of the initial states involving $b$-quarks and we introduce two $b$-jet tagging schemes.

• Mixed QCD-electroweak corrections to $Z$ and $W$ boson production and their impact on the $W$ mass measurements at the LHC

  Arnd Behring

  SciPost Phys. Proc. 7, 003 (2022) · published 20 June 2022 | Toggle abstract · pdf

  We report on recently computed mixed QCD-electroweak corrections to on-shell $W$ and $Z$ boson production. We use these differential predictions to estimate their impact on the $W$ boson mass determination at the LHC.

• New determination of the production cross section for secondary positrons and electrons in the Galaxy

  Luca Orusa, Mattia Di Mauro, Fiorenza Donato, Michael Korsmeier

  SciPost Phys. Proc. 13, 006 (2023) · published 28 September 2023 | Toggle abstract · pdf

  The cosmic-ray fluxes of electrons and positrons ($e^{±}$) are measured with high precision by the space-borne particle spectrometer AMS-02. To infer a precise interpretation of the production processes for $e^{±}$ in our Galaxy, it is necessary to have an accurate description of the secondary component, produced by the interaction of cosmic-ray proton and helium with the interstellar medium atoms. We determine new analytical functions of the Lorentz invariant cross section for the production of $e^±$ by fitting data from collider experiments. The total differential cross section $d\sigma/dT_{e^±}(p+p→ e^±+X)$ is predicted with an uncertainty of about 5-7% in the energies relevant for AMS-02 positron flux. For further information about this work refer to [Phys. Rev. D 105, 123021 (2022)].

• Combining QED and approximate ${\rm N}^3$LO QCD corrections in a global PDF fit: MSHT20qed_an3lo PDFs

  T. Cridge, L. A. Harland-Lang, R. S. Thorne

  SciPost Phys. 17, 026 (2024) · published 30 July 2024 | Toggle abstract · pdf

  We present the MSHT20qed_an3lo parton distribution functions (PDFs). These result from the first global PDF analysis to combine QED and approximate $N^3$LO (a$N^3$LO) QCD corrections in the theoretical calculation of the PDF evolution and cross sections entering the fit. We examine the PDF impact, and find that the effect of QED is relatively mild in comparison to the a$N^3$LO corrections, although it should still be accounted for at the level of precision now required. These QED corrections are in addition found to roughly factorise from the QCD corrections; that is, their relative impact on the PDFs is roughly the same at NNLO and a$N^3$LO. The fit quality exhibits a very small deterioration at a$N^3$LO upon the inclusion of QED corrections, which is rather smaller than the deterioration observed at NNLO in QCD. The impact on several cross-sections at $N^3$LO is also examined, including the Higgs cross sections at $N^3$LO. Finally, a LO in QCD fit that includes QED corrections is also presented: the MSHT20qed_an3lo set.

• Studying mass generation for gluons

  Gernot Eichmann, Jan M. Pawlowski

  SciPost Phys. Proc. 6, 018 (2022) · published 31 May 2022 | Toggle abstract · pdf

  In covariant gauges, the gluonic mass gap in Yang-Mills theory manifests itself in the basic observation that the massless pole in the perturbative gluon propagator disappears in nonperturbative calculations, but the origin of this behavior is not yet fully understood. We summarize a recent study of the respective dynamics with Dyson-Schwinger equations in Landau-gauge Yang-Mills theory. We identify the parameter that distinguishes the massive Yang-Mills regime from the massless decoupling solutions, whose endpoint is the scaling solution. Similar to the PT-BFM scheme, we find evidence that mass generation in the transverse sector is triggered by longitudinal massless poles.

• Inclusive decays of heavy quark hybrids

  Abhishek Mohapatra

  SciPost Phys. Proc. 6, 008 (2022) · published 31 May 2022 | Toggle abstract · pdf

  In order to understand the nature of the XYZ particles, theoretical predictions of the various XYZ decay modes are essential. In this work, we focus on the semi-inclusive decays of heavy quarkonium hybrids into traditional quarkonium in the EFT framework. We begin with weakly coupled potential NRQCD effective theory that describes systems with two heavy quarks and incorporates multipole expansions and use it to develop a Born-Oppenheimer effective theory (BOEFT) to describe the hybrids and compute the semi-inclusive decay rates. We compute both the spin-conserving and spin-flipping decay rates and find that our numerical results of the decay rates are different from the previous studies. We also develop a systematic framework in which the theoretical uncertainty can be systematically improved.

• The NFLikelihood: An unsupervised DNNLikelihood from normalizing flows

  Humberto Reyes-González, Riccardo Torre

  SciPost Phys. Core 7, 048 (2024) · published 31 July 2024 | Toggle abstract · pdf

  We propose the NFLikelihood, an unsupervised version, based on Normalizing Flows, of the DNNLikelihood proposed in [Eur. Phys. J. C 80, 664 (2020)]. We show, through realistic examples, how Autoregressive Flows, based on affine and rational quadratic spline bijectors, are able to learn complicated high-dimensional Likelihoods arising in High Energy Physics (HEP) analyses. We focus on a toy LHC analysis example already considered in the literature and on two Effective Field Theory fits of flavor and electroweak observables, whose samples have been obtained through the HEPFit code. We discuss advantages and disadvantages of the unsupervised approach with respect to the supervised one and discuss a possible interplay between the two.