Search of hybrids in multi-meson final states with the GlueX experiment at the Thomas Jefferson National Accelerator Facility (JLab)
Final Report Abstract
The topic of this fellowship was the search for states which contain a gluonic degree of freedom like hybrids or glueballs. For this, I joined the GlueX collaboration and started to work on final states containing two neutral mesons. Two different reactions γp → π 0 π 0 and pηη could successfully be extracted. Detailed investigation of the Dalitz plots revealed the occurrence of baryon and meson resonances. The usability of a van Hove selection, which could distinguish between these two different reaction types, was tested in detail and also simulated. It could be shown that a van Hove selection alone is not useful since it will also remove states with higher masses, which are of most interest in the search of glueballs and hybrids. The beam asymmetry Σ could be extracted in quasi two-body kinematics for both final states and for the different reaction topologies. In addition, observables in full threebody kinematics were extracted for the first time, however, their interpretation is still unclear. In close collaboration with the JPAC group, a moment analysis was performed for the first time, which is the first step towards the extraction of the full partial waves. From these moments, the beam asymmetry could also be extracted, which confirmed the previous measurements and verified the procedure of the moment analysis. During this fellowship, several contacts to researcher from GlueX experiment were build up and especially a close collaboration with members of the JPAC analysis team was initiated. A detailed investigation on the background contributions has started and first ideas about the modelling of the background were developed. This topic will become for major importance for the extraction of meson resonances at high energies and will most likely be also of importance for other new experiments, like the PANDA experiment, which is currently built up at FAIR at GSI.
Publications
- “Beam Asymmetry Σ for the Photoproduction of η and η Mesons at Eγ = 8.8GeV,” Phys. Rev. C 100, no. 5, 052201 (2019)
S. Adhikari et al. [GlueX Collaboration]
(See online at https://doi.org/10.1103/PhysRevC.100.052201) - “First Measurement of Near-Threshold J/ψ Exclusive Photoproduction off the Proton,” Phys. Rev. Lett. 123, no. 7, 072001 (2019)
A. Ali et al. [GlueX Collaboration]
(See online at https://doi.org/10.1103/PhysRevLett.123.072001)
