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.

• The diagrammatic coaction and cuts of the double box

  Einan Gardi, Aris Ioannou

  SciPost Phys. Proc. 7, 012 (2022) · published 20 June 2022 | Toggle abstract · pdf

  The diagrammatic coaction encodes the analytic structure of Feynman integrals by mapping any given Feynman diagram into a tensor product of diagrams defined by contractions and cuts of the original diagram. Feynman integrals evaluate to generalized hypergeometric functions in dimensional regularization. Establishing the coaction on this type of functions has helped formulating and checking the diagrammatic coaction of certain two-loop integrals. In this talk we study its application on the fully massless double box diagram. We make use of differential equation techniques, which, together with the properties of homology and cohomology theory of the resulting hypergeometric functions, allow us to formulate the coaction on a range of cuts of the double box in closed form.

• A new Wilson line-based classical action for gluodynamics

  Hiren Kakkad, Piotr Kotko, Anna Stasto

  SciPost Phys. Proc. 7, 011 (2022) · published 20 June 2022 | Toggle abstract · pdf

  We develop a new classical action that in addition to $\mathrm{MHV}$ vertices contains also $\mathrm{N^kMHV}$ vertices, where $1\leq k \leq n-4$ with $n$ the number of external legs. The lowest order vertex is the four-point MHV vertex -- there is no three point vertex and thus the amplitude calculation involves fewer vertices than in the CSW method. The action is obtained by a canonical transformation of the Yang-Mills action in the light-cone gauge, where the field transformations are based on Wilson line functionals.

  1 citation

• 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.

• Proving the dimension-shift conjecture

  Ruth Britto, Guy R. Jehu, Andrea Orta

  SciPost Phys. Proc. 7, 009 (2022) · published 20 June 2022 | Toggle abstract · pdf

  We prove the conjecture made by Bern, Dixon, Dunbar, and Kosower that describes a simple dimension shifting relationship between the one-loop structure of N = 4 MHV amplitudes and all-plus helicity amplitudes in pure Yang-Mills theory. The proof captures all orders in dimensional regularisation using unitarity cuts, by combining massive spinor-helicity with Coulomb-branch supersymmetry. The form of these amplitudes can be given in terms of pentagon and box integrals using a generalised D-dimensional

• 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.

• Two-parton scattering in the high-energy limit: climbing two- and three-Reggeon ladders

  G. Falcioni, E. Gardi, N. Maher, C. Milloy, L. Vernazza

  SciPost Phys. Proc. 7, 007 (2022) · published 20 June 2022 | Toggle abstract · pdf

  We review recent progress on the calculation of scattering amplitudes in the high-energy limit. We start by illustrating the shockwave formalism, which allows one to calculate amplitudes as iterated solutions of rapidity evolution equations. We then focus on our recent results regarding 2 -> 2 parton scattering. We present the calculation of the imaginary part of the amplitude, at next-to-leading logarithmic accuracy in the high-energy logarithms, formally to all orders, and in practice to 13 loops. We then discuss the computation of the real part of the amplitude at next-to-next-to-leading logarithmic accuracy and through four loops. Both computations are carried in full colour, and provide new insight into the analytic structure of scattering amplitudes and their infrared singularity structure.

  4 citations

• 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.

• On the discrepancy between the FOPT and CIPT approaches for hadronic tau spectral function moments

  Andre H. Hoang, Christoph Regner

  SciPost Phys. Proc. 7, 005 (2022) · published 20 June 2022 | Toggle abstract · pdf

  The discrepancy between the FOPT and CIPT approaches for hadronic tau spectral function moments constitutes the major theoretical uncertainty for strong coupling determinations from tau decay data. We show that the discrepancy can be analytically understood since the Borel representations -- which have been assumed to be identical for both approaches previously -- differ in the presence of IR renormalons. This implies that the OPE condensate corrections are different for both approaches and that the discrepancy may eventually be reconciled. In the talk we explain the difference and some mathematical aspects of the FOPT and CIPT Borel representations and show numerical results.

  2 citations

• NNLO EW⊗QCD corrections to on-shell Z production

  Narayan Rana

  SciPost Phys. Proc. 7, 004 (2022) · published 20 June 2022 | Toggle abstract · pdf

  In this proceeding, we outline the computational details and present the results for NNLO mixed EW⊗QCD corrections to on-shell production of Z boson at the LHC. We use the method of differential equation to obtain all the master integrals analytically, appearing in virtual and real-emission contributions. These results increase the accuracy of the predictions and contribute to reduce the theoretical uncertainties.

  1 citation