Proceedings Series

Vol. 17 (2024), No. 2, 22 Articles

The XLV International Conference of Theoretical Physics Matter to the Deepest

Ustroń, Poland; 17–22 September, 2023

Front Matter


Conference Programme

List of Participants

Status of the Superweak Extension of the Standard Model and Muon \(g-2\)


The super-weak force is a minimal, anomaly-free U(1) extension of the Standard Model, designed to explain the origin of (i) neutrino masses and mixing matrix elements, (ii) dark matter, (iii) cosmic inflation, (iv) stabilization of the electroweak vacuum, and (v) leptogenesis. In this paper, we discuss the phenomenological status of the model and provide viable scenarios for the physics of the items in this list.

all authors

R. Bonciani, V. Del Duca, H. Frellesvig, M. Hidding, V. Hirschi, F. Moriello, G. Salvatori, G. Somogyi, F. Tramontano

Exact Quark Mass Corrections to Higgs \(+\) Jet Production at the LHC


We present the computation of the next-to-leading order QCD corrections to the production of a Higgs boson in association with a jet at the LHC, including the exact dependence on the masses of quarks circulating in heavy-quark loops. The NLO corrections are computed including the top-quark mass as well as the bottom-quark mass. We show results in the on-shell and \(\overline {\mathrm {MS}}\) renormalisation schemes.

Entanglement Entropy and Proton’s Structure


We report on a study of a maximally entangled proton wave function in Deep Inelastic Scattering at low \(x\) and the proposed relation between parton number and final-state hadron multiplicity. We determine partonic entropy from the sum of the gluon function at low \(x\), which we obtain from an unintegrated gluon distribution subject to next-to-leading order Balitsky–Fadin–Kuraev–Lipatov evolution. We find for this framework very good agreement with H1 data.

How Well Could We Calculate Luminosity at FCCee?


In this note, we discuss the precision possible for the calculation of the small-angle Bhabha process that can serve as a luminosity monitor at the future FCCee collider. We present a refined, more aggressive version of the analysis done in the previous study. We conclude that the forecasted earlier precision of \(1\times 10^{-4}\) can be reduced to \(0.76\times 10^{-4}\) with the same calculational tools. We also analyse possibilities of a further reduction of the error to the close to \(10^{-5}\) precision regime. We discuss conditions necessary for such an ambitious goal.

Lightcone Expansion Beyond Leading Power


We discuss recent developments in descriptions of processes using power expansion around the lightcone within the Soft-Collinear Effective Theory. First, we present an overview of the systematically improvable framework that enables factorization of high-energy scattering processes beyond leading power in the expansion in ratios of energy scales. As an illustration of the relevant concepts, we describe the recently derived factorization theorem for the off-diagonal channel of the Drell–Yan production process at threshold. This example exposes endpoint divergences appearing in convolution integrals in factorization formulas. Lastly, we discuss the solution to these complications developed in the context of “gluon thrust” in \(e^+e^-\) collisions.

KrkNLO Parton Shower Matching


The consistent combination of Next-to-Leading-Order (NLO) perturbative QCD with the logarithmic resummation of parton shower algorithms (‘NLO matching’) is a workhorse of precision QCD in the LHC era. Two methods for achieving this have been widely adopted: Mc@Nlo and Powheg. The differences between them are formally Next-to-Next-to-Leading-Order (NNLO) and therefore irrelevant for NLO accuracy, but are nevertheless numerically significant for certain processes and observables. We summarise a third method, KrkNLO, and present preliminary phenomenological results from its implementation in Herwig 7.

Compatibility Between Theory Predictions at NNLO QCD Accuracy and Experimental Data for Top–Antitop Hadroproduction


We extract the top-quark mass value in the on-shell renormalization scheme from the comparison of theoretical predictions for \(pp \rightarrow t\bar {t} + X\) at next-to-next-to-leading order QCD accuracy with the experimental data collected by the ATLAS and CMS collaborations for absolute total, normalized single- and double-differential cross sections. For the theory computations, we use the MATRIX framework, interfaced to PineAPPL for the generation of grids of predictions, which are efficiently used a posteriori during the fit, performed within xFitter. We take several state-of-the-art parton distribution functions (PDFs). The results of the fit using as input different PDF sets agree with each other within 1\(\,\sigma \) uncertainty, whereas some datasets related to \(t\bar {t}\) decay in different channels point towards top-quark mass values in slight tension among each other, although still compatible within \(2.5\sigma \) accuracy. Our results are compatible with the PDG 2022 top-quark pole-mass value.

The Emission of Soft-photons and the LBK Theorem, Revisited


Predictions for processes involving soft photons, up to next-to-leading power (NLP) in the photon energy, can be obtained using the Low–Burnett–Kroll (LBK) theorem. The consistency of the theorem has been a recent topic of investigation since it is traditionally formulated in terms of a non-radiative amplitude, which is evaluated with unphysical momenta. We address such questions and propose a formulation of the LBK theorem which relies on the evaluation of the non-radiative amplitude with on-shell, physical momenta. We use this form to numerically study the impact of NLP contributions to cross sections for \(pp\) and \(e^-e^+\) processes involving soft-photon emission.

New Approach to Measuring Quark–Gluon Jets at the LHC


This paper describes a novel method for measuring quark/gluon jet properties at the Large Hadron Collider (LHC) at CERN. The advantage of this method is the use of data collected at different energies during LHC operation, allowing these data sets to be combined to obtain distributions of jet properties categorized into quark- and gluon-jet samples on a statistical basis. The method is presented with various angularity observables, and the search for the most useful observables is performed.

Tuning Herwig 7 with Lund String Model


We present selected results of a systematic study of non-perturbative effects of the Lund string hadronization model from Pythia 8 on top of the angular ordered parton shower in the Herwig 7 Monte Carlo Event Generator. We adopt the Professor approach to tune a set of model parameters to lepton- and hadron-collision data and compare obtained results to the default Herwig 7 tune, the Autotunes tune as well as the Pythia 8 tune.

all authors

R. Marzucca, A.J. McLeod, B. Page, S. Pögel, X. Wang, S. Weinzierl

Recent Developments from Feynman Integrals


This paper reviews recent developments in the field of analytical Feynman integral calculations. The central theme is the geometry associated to a given Feynman integral. In the simplest case, this is a complex curve of genus zero (aka the Riemann sphere). In this article, we discuss Feynman integrals related to more complicated geometries such as curves of higher genus or manifolds of higher dimensions. In the latter case, we encounter Calabi–Yau manifolds. We also discuss how to compute these Feynman integrals.

Geometrical Methods for the Analytic Evaluation of Multiple Mellin–Barnes Integrals


Two recently developed techniques of analytic evaluation of multifold Mellin–Barnes (MB) integrals are presented. Both approaches rest on the definition of geometrical objects conveniently associated with the MB integrands, which can then be used along with multivariate residues analysis to derive series representations of the MB integrals. The first method is based on introducing conic hulls and considering specific intersections of the latter, while the second one rests on point configurations and their regular triangulations. After a brief description of both methods, which have been automatized in the MBConicHulls.wl Mathematica package, we review some of their applications. In particular, we show how the conic hulls method was used to obtain the first analytic calculation of complicated Feynman integrals, such as the massless off-shell conformal hexagon and double-box. We then show that the triangulation method is even more efficient, as it allows one to compute these nontrivial objects and harder ones in a much faster way.

Series Expansion of Hypergeometric Functions About Their Parameters Using MultiHypExp


We describe our algorithm to find the series expansion of multivariate hypergeometric functions (MHFs) in \(\epsilon \) that lie in the Pochhammer parameters and its Mathematica implementation MultiHypExp.

Quantum Algorithms in Particle Physics


We motivate the use of quantum algorithms in particle physics and provide a brief overview of the most recent applications at high-energy colliders. In particular, we discuss in detail how a quantum approach reduces the complexity of jet clustering algorithms, such as anti-\(k_{\mathrm {T}}\), and show how quantum algorithms efficiently identify causal configurations of multiloop Feynman diagrams. We also present a quantum integration algorithm, called QFIAE, which is successfully applied to the evaluation of one-loop Feynman integrals in a quantum simulator or in a real quantum device.

Low-energy Constraints on the Effective Left–Right Symmetric Model’s Parameters


We discuss the Minimal Left–Right Symmetric Model (MLRSM) with and without non-renormalizable operators of dimension 6. We update a fit for MLRSM based on low-energy electron–hadron, neutrino–hadron, and neutrino–electron processes and consider one-loop effects for the neutrino–hadron process with left-handed neutrino and up-quark interactions. For the same process, we examine dimension-6 operators of the \(\phi ^2 X^2\) class and show predictions for relevant Wilson coefficients.

Precise Prediction for the \(W\)-boson Mass in U(1) Extensions of the Standard Model


We present the one-loop correction to the \(W\)-boson mass in U(1)\(_z\)-type extensions of the Standard Model. We compare it to an approximation, often used in high-energy physics tools. We point out that if the \(Z'\) boson — predicted in U(1)\(_z\)-type extensions — is much heavier than the \(Z\) boson, then the use of the complete set of one-loop corrections is necessary.

Real Effective Potentials for Phase Transitions in Models with Extended Scalar Sectors


The effective potential is a widely used phenomenological tool for investigating phase transitions occurring in the early Universe at finite temperature. In the standard perturbative treatment, the potential becomes complex in some region of the background field values due to the non-convex nature of the classical potential in models with spontaneous symmetry breaking. The imaginary part renders the minimization of the potential impossible when at finite temperature the absolute minimum is in the complex region. In this contribution, we introduce a simple method to calculate an effective potential that is fully real based on the optimized perturbation theory scheme. We apply the method for models that extend the Standard Model with an additional singlet scalar.

Present Status and Future Prospects of Neutrino Oscillation Experiments


In this contribution, we discuss the status of the currently running experiments and the capability of the future proposed experiments to study neutrino oscillation. In particular, we discuss the current results of the accelerator-based long-baseline experiments in the standard three-flavour scenario and for a scenario where one assumes the existence of a light sterile neutrino at the eV scale in addition to the three active neutrinos. Further, we also discuss the capability of the future long-baseline experiments to study these scenarios.

T2K Latest Results


T2K is a long baseline neutrino experiment producing a beam of neutrinos at the Japan Particle Accelerator Research Centre (J-PARC) and measuring their oscillation by comparing the measured neutrino spectrum at a near detector complex and at the water Cherenkov detector Super Kamiokande (Super-K), located 295 km away. In recent years, significant updates were applied to the T2K oscillation analysis, including: improved flux predictions, updated neutrino interaction modelling, and new selection samples in both near detector and Super-K. Current oscillation analysis results are presented with CP conservation excluded at the 90% confidence level. Additionally, an overview of T2K cross-section studies is discussed.

Phenomenology of Flavour (and CP) Symmetries


Flavour (and CP) symmetries can be the key to understanding fermion masses and mixing. In theories beyond the Standard Model, they can also be crucial in order to understand, for example, the suppression of certain flavour-violating signals and the correlation among the generated amount of baryon asymmetry of the Universe and the size of CP violation, potentially observable in neutrino experiments. We present two models, an extension of the Standard Model with a leptoquark and a dihedral flavour group as well as a low-scale type I seesaw scenario with a flavour and a CP symmetry.

Baryon Asymmetry of the Universe from Dark Matter Decay


We propose the baryon asymmetry of the Universe (BAU) to arise from forbidden decay of dark matter (DM) in the vicinity of a first-order phase transition (FOPT). In order to illustrate the idea, we consider the example of the minimal scotogenic model where the Standard Model is extended by three right-handed neutrinos (RHN) and a scalar doublet, all odd under an unbroken \(Z_2\) symmetry. The lightest RHN is the DM candidate, which can decay in the early Universe during a first-order electroweak phase transition, leading to the origin of BAU via leptogenesis. The stochastic gravitational wave background originating from the FOPT can be probed at near-future experiments like LISA, while all new fields remain in the TeV corner offering complementary detection prospects.

Recent Developments in Testable Leptogenesis


Low-scale leptogenesis is an attractive explanation for the observed baryon asymmetry of our universe that can be tested at a variety of laboratory experiments. In these proceedings, we review some recent advances in this field. In particular, we find that the viable parameter space is strongly enhanced, compared to the minimal case with two right-handed neutrinos, when a third generation is considered and explore the impact of such enhancement on the testability of the scenario. Finally, we also look at the impact of specific flavour and CP symmetries on said parameter space.


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