Conference Registration

Sinead Farrington - Highlights from Experiment and where next for precision

• Sinead Farrington

Alexander Penin - Higgs boson production at the next-to-next-to-leading power

• Alexander Penin (University of Alberta)

We study the amplitudes of the light quark mediated Higgs boson production via gluon fusion in the high-energy limit. A complete analytic result is obtained for the three-loop $O(m_q^3)$ double-logarithmic term while and the all-order analysis is performed in the large-$N_c$ limit of QCD and in the abelian approximation.

Gudrun Heinrich - Two Higgs bosons, two loops, x+2 operators

• Gudrun Heinrich (Karlsruhe Institute of Technology)

In the first part of the talk, methods for the calculation of two-loop amplitudes with several mass scales, such as HH, HJ or HZ production in gluon fusion, will be discussed. The second part will focus on Higgs boson pair production, in particular the combination of NLO QCD corrections with anomalous couplings in an Effective Field Theory framework. Predictions for the Higgs boson pair invariant mass spectrum, including leading operators as well as loop-suppressed operators such as 4-top-quark-operators, will be presented.

Bernhard Mistlberger - Approximations for LHC Cross Sections using Collinear Expansions

• Bernhard Mistlberger (SLAC)

Kinematic expansions of scattering cross sections provide powerful methods of approximating key LHC observables to a high degree of precision at reduced degree of complexity in comparison to a full computation. I will show several recent advancements and examples in the development and application of collinear expansion techniques.

Stefano Forte - Can we trust machine learning? PDFs as a case study

• Stefano Forte (Universita' di Milano)

I critically examine issues that arise when applying modern machine learning techniques in the context of precision collider physics, by specifically considering the case of PDF determinations. Questions that I address include: Can we trust the machine learning model to correctly generalize from known examples? How can we validate results, specifically for uncertainties? Can we detect over- and under-learning? Can a machine learning model detect inconsistencies in the data that it is being shown?

Kirill Melnikov - Power corrections to collider processes

• Kirill Melnikov (TTP KIT)

I will review novel developments related to an analytic understanding of power corrections to collider processes in the context of renormalon calculus.

Stefan Weinzierl - Feynman integrals, geometries and differential equations

• Stefan Weinzierl (University of Mainz)

We may associate a geometry to a Feynman integral. Understanding the geometry helps in computing the Feynman integral. In this talk I will discuss how Feynman integrals related to non-trivial geometries like Calabi-Yau manifolds can be computed with the help of the method of differential equations. In particular I will discuss an ansatz, which casts the differential equation into an epsilon-factorised form.

Lorenzo Magnea - Differential equations for parametrised Feynman integrals

• Lorenzo Magnea (University of Torino)

Following up on some distant and little-known papers by Tullio Regge and collaborators, I will present an approach to integration-by-parts identities and differential equations for Feynman integrals, based on the Feynman parameter representation, and relying upon the projective nature of parameter integrands. A very general identity connecting projective forms allows to move across families of Feynman integrals, unifying IBP identities and dimensional shifts, and feeding into systems of differential equations, similar but not identical to the conventional ones. I will illustrate the results with simple examples at one and two loops.

Sebastian Mizera - Landau Singularities Revisited

• Sebastian Mizera (Perimeter Institute for Theoretical Physics)

Landau analysis aims to predict the singularity structure of Feynman integrals without their explicit evaluation. We point out a number of errors in its textbook formulation that prevented applications to the Standard Model processes in the past. After resolving these issues, we use a combination of tropical analysis and numerical algebraic geometry to implement an algorithm that classifies and consistently finds all possible singularities of multi-loop Feynman integrals.

Thomas Gehrmann - Precision QCD calculations for vector boson observables

• Thomas Gehrmann (University of Zurich)

HuaXing Zhu - Power corrections to energy flow distribution meets conformal bootstrap

• HuaXing Zhu (Zhejiang University)

Dynamics of high energy scattering in QCD are primarily probed through detector energy flow correlations. One important IRC safe energy-flow observable is the Energy-Energy Correlator (EEC). At leading power approximation in the back-to-back limit, EEC enjoys a factorization formula similar to the Drell-Yan production at small transverse momentum. Therefor studying the power corrections to EEC provides valuable insight to power corrections to Drell-Yan production. In this talk I will introduce a novel method to calculate power corrections to EEC by exploiting the power of conformal symmetry. I will show that there is a close correspondence between power corrections on one side, and twist and large spin perturbation in the operator product expansion of local correlator on the other side. I will demonstrate the method by computing the first NLP resummation for EEC.

Martin Beneke - Gradient flow renormalon subtraction and the hadronic tau decay series

• Martin Beneke (Technische Universität München)

We subtract the gluon-condensate renormalon singularity in the Adler function, which causes the discrepancy between fixed-order (FOPT) and contour-improved perturbation theory (CIPT), employing the gradient flow action density. The scheme leads to automatic subtraction, does not require knowledge of the Stokes constant (renormalon residue), and relates to a non-perturbatively defined cut-off gluon condensate. Unlike unsubtracted perturbation theory, FOPT and CIPT give consistent results for the inclusive hadronic tau decay width, removing a major uncertainty in the determination of the strong coupling from tau decay.

Robert Szafron - Towards N3LL jet veto

• Robert Szafron (Brookhaven National Laboratory)

In my talk, I will present the calculation of the two-loop soft and beam functions for the transverse-momentum distribution of the leading jet in the production of a colour-singlet system such as a Higgs or Z boson. This calculation constitutes a vital component for the resummation of the transverse-momentum distribution and the jet-vetoed cross-section at next-to-next-to-next-to-leading logarithmic order (N3LL).

Michał Czakon - Jet and Photon Physics at high perturbative orders in QCD

• Michał Czakon (RWTH Aachen University)

I will present recently published as well as yet unpublished results on multi-photon and multi-jet cross sections obtained with next-to-next-to-leading and possibly higher order in perturbative QCD.

Organised excursions

Johannes Henn - Four-dimensional integration methods for Feynman integrals

• Johannes Henn (Max Planck Institute for Physics, Munich)

Peter Marquard - Three-loop massive form factors

• Peter Marquard (DESY)

Matthias Steinhauser - Analytic approximations of $2\to 2$ processes with massive internal particles

• Matthias Steinhauser (KIT)

We consider two-loop corrections to $2\to 2$ scattering processes with massive particles in the final state and massive particles in the loop. We discuss the combination of analytic expansions in the high-energy limit and for small Mandelstam variable~$t$. For the example of double Higgs boson production we show that the whole phase space can be covered and time-consuming numerical integrations can be avoided.

Ekta Chaubey - Two-loop QCD and QED corrections to light-by-light scattering

• Ekta Chaubey (ekta@lpthe.jussieu.fr)

In this talk we present the analytic results for two-loop QCD as well as QED corrections to light-by-light scattering including contributions due to massive internal fermions.

David Kosower - Universal Decomposition of Phase-Space Integrands

• David A Kosower (IPhT, CEA-Saclay)

One-loop integrands can be written in terms of a simple, process-independent basis. A similar basis exists for integrands of phase-space integrals for the real-emission contribution at next-to-leading order. The demonstration deploys techniques from computational algebraic geometry in order to partial-fraction integrands in a systematic way. This provides the first step towards a decomposition of phase-space integrals in a basis of master integrals.

Silvia Ferrario Ravasio - Pushing the accuracy of parton showers for hadron colliders

• Silvia Ferrario Ravasio (CERN)

Shower Monte Carlo generators simulate fully realistic collider events, and reproduce much of the data from the LHC and its predecessors. Their core is represented by Parton Shower~(PS) algorithms, which provide the inclusion of soft radiation and enable us to mimic a realistic high-multiplicity collider event. The flexibility of these tools comes at a cost of a lower accuracy, which can lead to large systematic uncertainties and compromise the physics potential of the LHC and future colliders. In this talk I will discuss the criteria introduced by the PanScales collaboration to assess the logarithmic accuracy of PS's. I will also show new results for the PanScales dipole showers, which represent the first family of dipole showers with demonstrated NLL accuracy for Drell-Yan and gluon-fusion production at hadron colliders.

Keith Ellis - Resummation Studies for LHC

• Keith Ellis (IPPP, Durham)