https://doi.org/10.1140/epjc/s10052-017-5248-0
Regular Article - Theoretical Physics
Comparison of two Minkowski-space approaches to heavy quarkonia
1
CFTP, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001, Lisbon, Portugal
2
Department of Physics and Astronomy, Iowa State University, Ames, IA, 50011, USA
3
Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001, Lisbon, Portugal
4
Departamento de Física, Universidade de Évora, 7000-671, Évora, Portugal
5
Department of Physics, College of William & Mary, Williamsburg, VA, 23185, USA
* e-mail: sofia.leitao@tecnico.ulisboa.pt
Received:
17
May
2017
Accepted:
22
September
2017
Published online:
23
October
2017
In this work we compare mass spectra and decay constants obtained from two recent, independent, and fully relativistic approaches to the quarkonium bound-state problem: the Basis Light-Front Quantization approach, where light-front wave functions are naturally formulated; and, the Covariant Spectator Theory (CST), based on a reorganization of the Bethe–Salpeter equation. Even though conceptually different, both solutions are obtained in Minkowski space. Comparisons of decay constants for more than ten states of charmonium and bottomonium show favorable agreement between the two approaches as well as with experiment where available. We also apply the Brodsky–Huang–Lepage prescription to convert the CST amplitudes into functions of light-front variables. This provides an ideal opportunity to investigate the similarities and differences at the level of the wave functions. Several qualitative features are observed in remarkable agreement between the two approaches even for the rarely addressed excited states. Leading-twist distribution amplitudes as well as parton distribution functions of heavy quarkonia are also analyzed.
© The Author(s), 2017
