YOUNGST@RS - EFTs and Beyond

3 Dec 2024, 10:00 → 5 Dec 2024, 17:30 Europe/Berlin

Mainz Institute for Theoretical Physics, Johannes Gutenberg University

Effective field theories (EFTs) have been the main driving force in our increased understanding of Quantum Field Theory in the last few decades, both from the conceptual and computational perspectives.

"EFTs and Beyond" is a fully online workshop, co-organized by MITP, that will focus on recent developments and applications of Effective Field Theories. It will take place from December 3rd to 5th, 2024.

We are particularly interested in showcasing the work of early-career researchers. We plan to have approximately 6-10 talks per day, presented by PhD students and postdocs, covering three main topics:

• Standard Model as an Effective Field Theory
• Computational Tools and Methods in EFTs
• EFTs in the Standard Model and Beyond

Each day will begin with an introduction given by an expert and senior scientist, setting the stage for the day's discussions and talks. In addition, a virtual roundtable will encourage discussions and foster the exchange of ideas on various aspects of EFTs.

Feel free to reach out to us if you have any questions!

Lukas Born, Marta Fuentes Zamoro, Ajdin Palavrić and Marko Pešut, organizing committee

Tuesday 3 December

10:00 → 10:10 Welcome Greeting by MITP Directors

10:10 → 11:40 Talk (COMP): Computational Tools and Methods in EFTs

Convener: Marko Pesut (University of Zürich)

10:10 TBD

Speaker: Anders Eller Thomsen (University of Bern)

11:10 Constraining the SMEFT from electroweak, Higgs-boson, and top-quark observables

We present results from a global fit of dimension-six SMEFT operators that includes electroweak, Higgs-boson, and top-quark observables. The leading-order scale dependence of the SMEFT Wilson coefficients is consistently included in the evolution from the UV scale to the scale of the observables. In defining the SMEFT set of active operators we consider both the $U(3)^5$ and the $U(2)^5$-symmetric limits. The global fit is obtained within the HEPfit framework and is based on the state-of-the-art of both experimental results and theoretical predictions for all the observables considered.

Speaker: Victor Miralles (University of Manchester)

11:40 → 11:45 Coffee break

11:45 → 12:45 Talk (COMP): Computational Tools and Methods in EFTs

Convener: Marko Pesut (University of Zürich)

11:45 Renormalization group equations via on-shell methods

We elaborate on the application of on shell and unitarity-based methods for evaluating renormalization group coefficients, and generalize this framework to account for the mixing of operators with different dimensions and leading mass effects. We derive a master formula for anomalous dimensions stemming from the general structure of operator mixings, up to two-loop order, and show how the Higgs low-energy theorem can be exploited to include leading mass effects. A few applications on the renormalization properties of popular effective field theories showcase the strength of the proposed approach, which drastically reduces the complexity of standard loop calculations. Our results provide a powerful tool to interpret experimental measurements of low-energy observables, such as flavor violating processes or electric and magnetic dipole moments, as induced by new physics emerging above the electroweak scale.

Speaker: Luigi Carlo Bresciani (University of Padova & INFN-PD)

12:15 Interplay of SMEFT and PDFs in global fits

The interpretation of hadron collider, such as the LHC, data, and the assessment of possible hints of new physics, require the precise knowledge of the proton structure in terms of parton distribution functions (PDFs). In this talk, I present a systematic methodology designed to determine whether and how global PDF fits might inadvertently 'fit away' signs of new physics in the high-energy tails of the distributions. I showcase a scenario for the High- Luminosity LHC, in which the PDFs may completely absorb such signs of new physics, thus biasing theoretical predictions and interpretations. I discuss strategies to single out the effects in this scenario and disentangle the inconsistencies that stem from them. A first solution I discuss is the exploration of the synergy between the high luminosity programme at the LHC and present and future low-energy measurements of large-sea quark distributions. A second one, is to fit simultaneously the PDFs and the new physics signals, which can be done using our publicly released open-source tool SIMUnet.

Speaker: Elie Hammou (University of Cambridge)

12:45 → 14:00 Lunch

14:00 → 15:00 Talk (COMP): Computational Tools and Methods in EFTs

Convener: Marko Pesut (University of Zürich)

14:00 Functional Multi-loops Matching

Functional Methods have emerge as a crucial tool for the automation of computations in quantum field theory, particularly in the renormalization and running of theories. On top of that, these techniques can be applied to the world of EFTs through the process of matching. So far this idea has been applied up to one loop. I present a systematic procedure for going beyond, considering both fermionic and bosonic degrees of freedom. I will demonstrate how the inclusion of gauge bosons requires a new approach to the problem that was not necessary in the one-loop case. It will rely on the introduction of the Wilson line to obtain a covariant expansion.

Speaker: Adrián Moreno Sánchez (Universidad de Granada)

14:30 An efficient tool for on-shell matching for effective field theories

We propose an efficient method to perform on-shell matching calculations in effective field theories. The standard off-shell approach to matching requires the use of a Green's basis that includes redundant and evanescent operators. However, on-shell matching allows to perform the matching directly to the physical basis. Our proposal is based on a numerical solution of the corresponding on-shell matching equations. The use of rational on-shell kinematics ensures an exact analytic solution despite the numerical procedure. We present the algorithm and some further applications, such as the automation of the Green’s basis reduction or the obtaining of evanescent contributions.

Speaker: Fuensanta Vilches Bravo (Departamento de Física Teórica y del Cosmos, Universidad de Granada)

15:00 → 15:15 Coffee break

15:15 → 16:15 Talk (COMP): Computational Tools and Methods in EFTs

Convener: Marko Pesut (University of Zürich)

15:15 Fixing the dynamical evolution of self-interacting vector fields

Numerical simulations of the Cauchy problem for self-interacting massive vector fields often face instabilities and apparent pathologies. We explicitly demonstrate that these issues, previously reported in the literature, are actually due to the breakdown of the well-posedness of the initial-value problem. This is akin to shortcomings observed in scalar-tensor theories when derivative self-interactions are included. Building on previous work done for k-essence, we characterize the well-posedness breakdowns, differentiating between Tricomi and Keldysh-like behaviors. We show that these issues can be avoided by ``fixing the equations'', enabling stable numerical evolutions in spherical symmetry. Additionally, we show that for a class of vector self-interactions, no Tricomi-type breakdown takes place. Finally, we investigate initial configurations for the massive vector field which lead to gravitational collapse and the formation of black holes.

Speaker: Marcelo Rubio (Gran Sasso Science Institute (GSSI, L'Aquila, Italy))

15:45 TBD

TBD

Speaker: Jason Aebischer (CERN)

Wednesday 4 December

10:00 → 11:30 Talk (SMEFT): Standard Model as an Effective Field Theory

Convener: Marko Pesut (University of Zürich)

10:00 TBD

TBD

Speaker: Ilaria Brivio (University & INFN Bologna)

11:00 Probing new physics at colliders via HEFT

Due to the lack of direct evidence in the search for new physics (NP), the Effective Field Theory (EFT) framework offers an indirect and model-independent approach to parameterize NP effects. In this talk, I will focus on the non-linear EFT framework, also known as Higgs Effective Field Theory (HEFT), and include next-to-leading order (NLO) bosonic operators to study Higgs-related processes at current and future colliders. First, using the Higgs propagator corrections, I will revisit the measurement of off-shell Higgs boson contribution in massive gauge boson pair production. Then, by including radiative corrections within HEFT, I will discuss the sensitivity of single-Higgs data to quartic Higgs-gauge interactions. Finally, I will highlight the impact of one-loop HEFT modifications to the Higgs-self couplings and their effects on multi-Higgs production.

Speaker: Anisha Anisha (Karlsruhe Institute of Technology)

11:30 → 11:45 Coffee break

11:45 → 12:45 Talk (SMEFT): Standard Model as an Effective Field Theory

Convener: Marko Pesut (University of Zürich)

11:45 SMEFT Global Analyses: NLO contributions, RGE effects and Flavour physics

The Standard Model Effective Field Theory (SMEFT) is an essential tool for probing physics beyond the Standard Model. With New Physics signals remaining elusive, deriving constraints on SMEFT Wilson coefficients is increasingly important in order to pinpoint its low-energy effects. This talk presents comprehensive global fits of SMEFT under the Minimal Flavour Violation (MFV) hypothesis. We establish global limits on Wilson coefficients using both leading and next-to-leading order SMEFT predictions for various observables. Our findings highlight significant interactions among different observables, emphasizing the necessity of integrating diverse data from multiple energy scales in global SMEFT analyses. Even within this flavour-symmetric framework, where Flavour Changing Neutral Currents (FCNC) cannot be generated at tree-level, they significantly contribute via Renormalization Group Evolution (RGE) effects. More in general a consistent treatment of the RGE in global analyses is an often-overlooked aspect which proves to be crucial for analysing properly datasets spanning various energy scales.

Speaker: Riccardo Bartocci (JGU Mainz)

12:15 Two-Loop Dimension-Six Effective Action: Integrating Out Heavy Scalar(s)

We have, for the first time, computed a model-independent two-loop dimension-six effective action by integrating out heavy scalars. As an example, we applied this to the electroweak complex triplet scalar and the 2HDM model. In this talk, I will discuss our approach to computing the two-loop effective action using the Heat-Kernel method, which simplifies the process by avoiding extensive Feynman diagrams and complex momentum integrals. Our approach applies to any theory with a second-order elliptic operator, enabling us to compute quantum corrections from Heat Kernel Coefficients (HKCs). This method yields universal results for models with scalar and fermion fields, making it a powerful tool for applications such as the Standard Model Effective Field Theory (SMEFT).

Speaker: Debmalya Dey (Indian Institute of Technology Kanpur)

12:45 → 14:00 Lunch

14:00 → 15:00 Talk (SMEFT): Standard Model as an Effective Field Theory

Convener: Marko Pesut (University of Zürich)

14:00 (Flavour) Constraints on Down-Type Diquarks

Scalar Diquarks which only couple to right-handed down-type quarks are difficult to resolve at colliders due to being able to hide amongst jet backgrounds. Using Standard Model Effective Field Theory we can also find indirect constraints on these diquarks from observables in flavour physics such as neutral meson oscillations and meson decays. Comparing current measurements from colliders and flavour physics we can show that while each test different regions in the diquark parameter space, both combined can rule out down-type diquarks below multi-TeV scales.

Speaker: Christiane Mayer (University of Zürich)

14:30 Using flavour to simplify running in the LEFT

The plethora of new precision measurements below the electroweak scale holds substantial significance for models of heavy new physics. To fully utilise these measurements, we must understand the running of the many operators of the Low Energy Effective Field Theory (LEFT). In this talk, I outline how decomposing operators according to their flavour and parity symmetries can simplify the running, making the map from electroweak scale to b-mass scale semi-analytically solvable. I will also discuss the applications of this work to flavour phenomenology.

Speaker: Ben Smith (University of Glasgow)

15:00 → 15:15 Coffee break

15:15 → 16:45 Talk (SMEFT): Standard Model as an Effective Field Theory

Convener: Marko Pesut (University of Zürich)

15:15 SMEFT analysis of charged lepton flavor violating B-meson decays

Charged lepton flavor violation (cLFV) processes, potentially important for various beyond the Standard Model physics scenarios are analyzed in the Standard Model effective field theory framework. We consider the most relevant two-quark–two-lepton (2q2ℓ) operators for the leptonic and semileptonic LFV B-decay (LFVBD) processes Bs→μ+e-,B+→K+μ+e-,B0→K0μ+e-, and Bs→ϕμ-e+. We analyze the interplay among the Wilson coefficients responsible for these LFVBDs and other cLFV processes, like CR(μ→e), ℓi→ℓjγ, ℓi→ℓjℓkℓm, and Z→ℓiℓj, to find the maximal possible LFV effects in B-meson decays. We probe the scale of new physics in relation to the constraints imposed by both classes of the LFV decays while considering both the present bounds and future expectations. In view of proposed experiments at LHCb-II and Belle II to study charged LFV processes, we have also provided the upper limits on the indirect constraints on such LFVBDs. For the processes where the B meson is decaying to μ± and e∓, we show that new physics can be constrained by an enhancement of 2–4 orders of magnitude on the current sensitivities of the branching ratios of B+→K+μ+e-,B0→K0μ+e-, and Bs→ϕμ±e∓.

Speaker: Rajeev Rajeev (PRL, Ahmedabad (India))

15:45 Two-loop running effects in Higgs physics in Standard Model Effective Field Theory

We consider the renormalization group equations within the Standard Model Effective Field Theory and compute two-loop contributions proportional to the top quark Yukawa coupling for the operator generating an effective Higgs-gluon coupling, focusing on the Yukawa-like operator. These two-loop running effects are relevant for processes where the effective Higgs-gluon coupling contributes at a lower loop order compared to the Standard Model contribution and where a dynamical scale choice is adopted. Such a situation arises, for instance, in the Higgs transverse momentum distribution and Higgs pair production. We investigate the phenomenological impact of our computations on these two processes and find that the two-loop contributions are significant and can lead to deviations of up to 20% in the scenarios we consider.

Speaker: Stefano Di Noi (KIT (ITP))

16:15 CP violation in SMEFT loop-induced diboson production

We study CP violation within the Standard Model Effective Field Theory framework, focusing on the impact of CP-odd dimension-6 operators entering gluon-induced double Higgs and double Z and W production. After extending the SMEFTatNLO model to include the relevant operators, we study differential distributions for these processes and compare their features to those obtained from CP-conserving interactions. For electroweak gauge boson production, we explore the impact of the new interactions on the angular distributions of the leptonic decay products and the associated gauge boson polarisation fractions both at the inclusive and differential level. This abstract is based primarily on the work done in arXiv: 2411.00959.

Speaker: Marion Thomas (University of Manchester)

Thursday 5 December

10:00 → 11:30 Talk (EFTs and Beyond): EFTs in the Standard Model and Beyond

Convener: Marko Pesut (University of Zürich)

10:00 TBD

TBD

Speaker: Claudia Cornella (CERN)

11:00 Mapping New Physics to Observables within the SMEFT Paradigm

The limitations of the Standard Model (SM) continue to drive the search for new physics. In the absence of direct evidence, performing a comparative analysis of various 'well-motivated' Beyond Standard Model (BSM) models under a common framework is valuable. Effective Field Theories (EFTs) offer a robust approach for such analyses, providing essential tools for systematic exploration, at distinct energy scales. This talk has two main objectives: first, to discuss the computation of the universal effective action up to dimension-eight using the Heat-Kernel method, advancing precision beyond dimension-six results; and second, to examine cases where dimension-eight contributions become more significant than dimension-six terms. Finally, we will explore two UV models containing heavy scalars - a complex scalar triplet and a doublet - as examples to show how integrating out heavy scalars and matching to UV parameters can effectively distinguish between these models.

Speaker: Tisa Biswas (Indian Institute of Technology, Kanpur)

11:30 → 11:45 Coffee break

11:45 → 12:45 Talk (EFTs and Beyond): EFTs in the Standard Model and Beyond

Convener: Marko Pesut (University of Zürich)

11:45 Fermionic UV models for neutral triple gauge boson couplings

Searches for anomalous neutral triple gauge boson couplings (NTGCs) can provide important tests for the gauge structure of the Standard Model (SM). The leading SMEFT contribution to NTGCs appears at dimension-8 and four different CP-conserving operators are required to describe correctly all possible NTGC form factors. We study a variety of extensions of the SM with heavy vector-like fermions and calculated their matching to SMEFT dimension-8 NTCG operators. Despite stringent experimental constraints on NTGCs the limits on the scale of these UV models are relatively weak because their contributions, arising at dimension-8 and 1-loop, are doubly suppressed. I will present benchmark UV scenarios that are suited for interpreting searches for NTGCs in the upcoming LHC runs, their current limits and estimates for the expected sensitivity of the high-luminosity LHC.

Speaker: Fabian Esser (Charles University Prague)

12:15 Radiative corrections to $\mathcal{B}\rightarrow \ell \nu$

In this talk I will focus on the study of the leptonic $\mathcal{B}\rightarrow \ell \nu$ at next-to-leading order in QED. The future improvements of experimental measurements of this channel require a reliable theory prediction, hence a careful theoretical estimate of QED corrections. The multi-scale character of this process requires an appropriate effective theory (EFT) construction to factorize the different contributions. In the first part of this talk, I will discuss the EFT description of the process at the partonic level, which is based on Heavy Quark Effective Theory and Soft Collinear Effective Theory. I will show how the inclusion of QED corrections demands a generalisation of the hadronic decay constant . In the second part of the talk, I will discuss the EFT description below the confinement scale using a point-like description for the B-meson. I will show that depending on the cut on final state radiation and on the lepton flavor the contribution from excited states of the B meson can become important.

Speaker: Max Ferré (JGU (Mainz))

12:45 → 14:00 Lunch

14:00 → 15:00 Talk (EFTs and Beyond): EFTs in the Standard Model and Beyond

Convener: Marko Pesut (University of Zürich)

14:00 EFTs for low-energy probes of high-energy physics (preliminary)

TBD

Speaker: Fiona Kirk (PTB Braunschweig & Leibniz University Hannover)

14:30 The "Deformed" Type-2 Seesaw Mechanism

The juxtaposition of the precision of lepton flavour measurements and the limited energy range of the Large Hadron Collider (LHC) to discover dynamical degrees of freedom linked to the generation of the observed lepton mass patterns naively suggests only a limited relevance of the LHC’s high luminosity phase. This, potentially, extends to future colliders. Using the concrete example of the type-II seesaw model and its effective field theory extension, we show that blind directions create a rich phenomenological interplay of muon precision measurements and electroweak resonance searches at present and future colliders, with testable implications for the HL-LHC phase.

Speaker: Wrishik Naskar (University of Glasgow)

15:00 → 15:15 Coffee break

15:15 → 16:15 Talk (EFTs and Beyond): EFTs in the Standard Model and Beyond

Convener: Marko Pesut (University of Zürich)

15:15 Gravitational Waves from Amplitudes and EFT

Recent years have seen significant advancements in employing tools from Quantum Field Theory, specifically techniques from the modern Amplitudes program, to inform theoretical predictions for gravitational waveforms generated by binary systems. In this talk I will review this effort, emphasizing especially two aspects: 1. Modeling the spin of astrophysical objects will become increasingly important for signal identification as the sensitivity of gravitational-wave detectors will continue to improve. I will discuss how using Amplitudes methods we have obtained new results pertaining to the gravitational interaction of spinning objects and identified novel physical phenomena that may manifest in the gravitational waveform. 2. Extreme-mass-ratio binary systems will be a significant source of gravitational-wave signals for the Laser Interferometer Space Antenna (LISA). I will introduce a Quantum Field Theoretic framework for modeling such systems, which leverages exact solutions to Einstein’s equations to compute classes of contributions to all orders in the gravitational coupling G but as an expansion in the mass ratio. I will conclude by discussing the next steps towards meeting the precision goals of the future gravitational-wave observatories.

Speaker: Dimitrios Kosmopoulos (University of Geneva)

15:45 Effect of NLO QCD corrections on anglular observables sensitive to anomalous $HZZ$ coupling at electron-proton collider

Properties of the Higgs boson ($H$) at current and future particle colliders are crucial to explore new physics beyond the standard model. In particular, experimental and theoretical outlooks at future colliders drive interest in Higgs to gauge boson couplings. Single Higgs production via vector-boson fusion allows probing Higgs couplings with massive vector bosons ($V = W, Z$). We consider electron-proton (eP) collider to study these couplings due to the low background. In a recent study, we considered the most general anomalous Higgs-vector boson ($HZZ$) couplings and explored the potential of eP collider in constraining the parameters of $HZZ$ couplings. Our results were based on leading order predictions in perturbation theory. We include further Next to Leading Order (NLO) corrections of Quantum Chromodynamic (QCD) in Standard Model signal to make precise predictions. In this talk, I will present the effect of NLO QCD corrections on the standard model and anomalous $HZZ$ couplings.

Speaker: Pramod Sharma (IISER Mohali. India)