time-like observables from multi-level lattice QCD

Projektinformationen

multiQCD

ID Finanzhilfevereinbarung: 843134

DOI

10.3030/843134

Projekt abgeschlossen

EK-Unterschriftsdatum 11 April 2019

Startdatum 1 November 2019

Enddatum 31 Oktober 2021

Finanziert unter

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Gesamtkosten

€ 191 149,44

EU-Beitrag

€ 191 149,44

Koordiniert durch

ORGANISATION EUROPEENNE POUR LA RECHERCHE NUCLEAIRE
Switzerland

Periodic Reporting for period 1 - multiQCD (time-like observables from multi-level lattice QCD)

Berichtszeitraum: 2019-11-01 bis 2021-10-31

Zusammenfassung vom Kontext und den Gesamtzielen des Projekts

The Standard Model (SM) of particle physics is the most successful theory of high-energy physics (HEP). It encompasses three of the four fundamental forces of nature, the electromagnetic, weak and strong forces, under the same mathematical framework of a gauge quantum field theory. With the discovery of the Higgs boson at CERN in 2012, which is responsible for giving to the masses of the elementary particle, the SM is now complete.
However, the SM does not explain all known phenomena in HEP. Among other things, it does not account for neutrino masses and oscillations, and it does not include dark matter, dark energy, and a quantum theory of gravitation.
To be able to understand if any experimental signature is a further indication of physics beyond the SM, one needs to be able to make precise predictions within the SM. My research focuses specifically on Quantum Chromodynamics (QCD), the sector of the SM responsible for the strong force that binds quarks into nucleons and nucleons into atomic nuclei. Because of their very nature of being strong interactions, the best methods to make predictions in the regime in which nucleons and nuclei form require expensive numerical simulations of the theory discretized on a four-dimensional lattice.
The ultimate goal of my research is to improve the understanding of these nuclear forces. Specifically, I am targeting the so-called time-like quantities that have so far eluded precise estimations due to the specific time-like kinematic regime, which renders them intrinsically hard and particularly expensive for standard numerical simulations of QCD on the lattice.

Arbeit, die ab Beginn des Projekts bis zum Ende des durch den Bericht erfassten Berichtszeitraums geleistet wurde, und die wichtigsten bis dahin erzielten Ergebnisse

During the two-year period of the programme I worked on pushing the frontier of the size, or volume, of the QCD lattices that can be simulated.
Having access to a very large volume meant much more information. However, not all this information is readily accessible. New techniques to compute time-like quantities have been developed. These include the so-called position-space methods, which make use of the correlation functions on a large volume as a function of the four-dimensional distance, instead of projecting to a sector with definite momentum.
In parallel, work has been carried out on the study of the spectral function of the electromagnetic current correlator in QCD at non-zero temperatures, which has a number interesting applications to observables such as the thermal production rate of photons by the quark-gluon plasma (QGP), deep-inelastic scattering on the QGP, and the hadronic vacuum polarization and its contribution to the anomalous magnetic moment of the muon.
The results have been published in peer-reviewed journal articles, and they have been presented at various workshops and at the main conference of the field, the 2021 instalment in the “International Symposium on Lattice Field Theory” series, both by me and by my collaborators.

Fortschritte, die über den aktuellen Stand der Technik hinausgehen und voraussichtliche potenzielle Auswirkungen (einschließlich der bis dato erzielten sozioökonomischen Auswirkungen und weiter gefassten gesellschaftlichen Auswirkungen des Projekts)

The configuration of the lattice gauge field of QCD that I contributed generation, with more than a billion lattice points, are among the biggest ever simulated, setting a new state-of-the-art standard for simulations in a large volume.
This has a direct impact on the precision to which we can extract hadronic quantities, which is a crucial step in performing the hard task of reconstructing time-like information.
In particular, we showed that the so-called position space methods are effective to compute simple hadronic quantities like the masses for pseudoscalar mesons and nucleons.
Further work is already ongoing to exploit the new techniques and the available gauge field configurations with the aim of pushing the precision frontier for time-like quantities.
Like all fundamental research in particle physics, my research has a large indirect impact on society. It has been estimated that for every Swiss franc spent by the taxpayer in research at CERN pays back approximately 1.8 Swiss francs in societal benefits.
A large fraction of the applications are in medical and biomedical technology. For example, understanding QCD is fundamental for hadron therapy, in which a beam of accelerated strongly-interacting particles is used for cancer treatment.

effective mass of the pion computed using position-space methods

slice of the gradient-flowed topological charge density on a large-volume gauge field configuration