Project Details
Projekt
The confined gluon: precision spectroscopy with charm quarks
Applicants
Professor Dr. Francesco Knechtli; Dr. Tomasz Korzec
Subject Area
Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 451886959
Flavor-singlet hadrons with masses in the range between 1 GeV and 3 GeV are extremely interesting to study both experimentally and theoretically. At the start of the millennium a number of entirely unexpected narrow resonances, called X, Y and Zs were discovered by the Belle and BaBar experiments and much more effort has been put into these systems in the following years. Many of these exotic states contain a charm anti-charm quark pair. Nevertheless the internal mechanics of these resonances remain largely obscured. Lattice QCD is a perfect theoretical tool to shed light onto these systems and that is one of the main goals of this research unit. With the tools and techniques developed in the first funding period we are now in the position to map out the quark-mass dependence of the finite volume energy spectra of QCD in several flavour-singlet symmetry channels, including all charm-annihilation effects. The latter often neglected contributions are particularly difficult to compute precisely, but at the same time are crucial to understand the mixing between charmonia, glueballs and lighter mesons like e.g. f0(500) and f0(980), and the decay into two or more mesons. That their precise calculation now became possible is due to our advances in simulation techniques, linear solvers, and operator construction methods, based on improved distillation, as well as utilization of modern GPU architectures. At high quark masses the spectra will clarify what happens to the glueballs of pure Yang-Mills theory, once quarks are added to the system. Their fate is then closely tracked when the quark masses are lowered and decay channels open. A scattering analysis a la Lüscher becomes necessary and will yield insight on resonance parameters of glueballs and other resonances like the f0(980). Similar methods will be applied to the study of the scattering of D-meson with D*-anti-meson and the X(3872) resonance. A complementary approach to understanding exotic quarkonia is by effective theories. Important inputs to theories like the Born-Oppenheimer effective theory are static potentials, which are being computed in lattice QCD. The ordinary static potential and "hybrid potentials", i.e. systems with intrinsic gluons are being investigated. In the second funding period the focus will lie on the phenomenon of string-breaking of such hybrid potentials together with measurements of the spectrum of QCD with an ajoint color source.
DFG Programme
Research Units
International Connection
Ireland
Co-Investigators
Professorin Dr. Nora Brambilla; Professor Dr. Jochen Heitger
Cooperation Partners
Professor Dr. Michael Peardon; Dr. Juan Andres Urrea-Nino
