Session Y12: Photo-Production of Hadrons III

Live

I'll present the latest results from the JPAC collaboration concerning photo- and hadro-production of two mesons in the high mass region. In this regime, the mesons are produced by double Regge exchanges. The application of double Regge phenomenology to the recent GlueX and COMPASS data will be presented.   

Live

A long-standing goal of hadron physics has been to understand how the quark and gluon degrees of freedom that are present in the fundamental QCD Lagrangian manifest themselves in the spectrum of hadrons. The GlueX experiment at Jefferson lab contributes to the global spectroscopy program using 8-9~GeV linearly polarized photons. This experiment focuses on the exploration of the light-quark domain, potentially accessing hybrid mesons with exotic $J^{PC}$ quantum numbers in photoproduction reactions. \par The decay of several exotic mesons (e.g.\ $\pi_1(1600)$, etc.)\ to $b_1 \pi$ can be accessed through the dominant decay $b_1 \rightarrow \omega \pi$. In this talk we discuss the channel $\gamma p \rightarrow p b_{1} \pi^{0} $, where the axial-vector meson $b_1$(1235)-neutral decays to $\omega \pi^{0}$. Understanding this channel is important, particularly in the context of Partial Wave Analysis and being able to extract the D/S wave ratio, which is of interest to validate predicted couplings to this axial-vector resonance from Lattice QCD calculations.   

Live

Signals for mesons with exotic $J^{PC}$ quantum numbers, which are not allowed for a quark-antiquark pair, have been experimentally observed, but their exact nature is still unknown. A candidate for these exotics is the hybrid meson, which consists of a quark, an antiquark, and an excited gluonic field configuration. GlueX, which is a large acceptance photoproduction experiment in Jefferson Lab's Hall D, aims to map the spectrum of light-quark mesons by studying a multitude of final states. The lightest expected exotic hybrid meson with $J^{PC} = 1^{-+}$ has been predicted to decay predominantly to $b_{1} \pi$, in a recent calculation by the HadSpec Collaboration. Thus, understanding the decay of the axial-vector $b_1$ meson is an important step in the search for exotics. In this talk, studies of the reaction $\gamma p \rightarrow \Delta^{++} \omega \pi^{-}$ at GlueX will be presented, with an emphasis on the amplitude analysis of the $\omega \pi^{-}$ final state, which is the dominant decay mode of the $b_{1}^{-}$.   

Live

Radiative decays of hyperons are sensitive to their internal structure and a clean probe of their underlying SU(3) wave function. So far only a few measurements of radiative decays of excited hyperons have been published. In this study we focus on the radiative decay of $\Sigma^{0}(1385)\to\Lambda\gamma$, where the excited hyperon is produced in photoproduction. The branching ratio of this particular decay has previously been measured in [1]. The GlueX experiment at Jefferson Lab provides excellent opportunities to study excited state hyperons in general and the reaction above in particular in photoproduction with a photon beam of $6.0 - 11.6~$GeV incident on a liquid hydrogen target with high statistics. This data sample is expected to have up to an order of magnitude more statistics than previously available. In this talk, we will discuss the ongoing analysis effort for the reaction $\gamma p\to K^+\Sigma^0(1385)\to K^+\Lambda\gamma$, emphasizing the reduction of the dominant background $\Sigma^{0}(1385)\to\Lambda\pi^0$. \begin{thebibliography}{xxx} \bibitem[1]{KELLER} Electromagnetic Decay of $\Sigma^{0}(1385)$ to $\Lambda\gamma$, D. Keller et. al (The CLAS collaboration), Phys. Rev. D 83, 072004, 2011 \end{thebibliography}   

Live

The GlueX experiment at Jefferson Lab aims to study the light meson spectrum with an emphasis on the search for hybrid mesons. A tagged photon beam, with energies in the range 3—11.6 GeV is incident on a hydrogen target inside a detector with near-complete neutral and charged particle coverage. The experiment completed its first phase of data taking in 2018, producing orders of magnitude more data than previous photoproduction experiments in this energy regime. A good theoretical description of the production mechanisms will be needed to interpret any potential signals for exotic mesons. Photoproduction data on conventional mesons is very useful for this purpose, where the energy and t-dependence of production cross sections are complementary to polarization observables. We present new, high-statistics measurements of the cross section for exclusive photoproduction of $\omega(782)$ mesons.   

Live

In this talk, we will present our revisited approach to the $\omega \to 3 \pi$ decay, in view of recent new measurements by BESIII collaboration. We will also discuss our progress on the $\phi \to 3\pi$ decays. Both decays are studied within the framework of Khuri-Treiman equations, for which we will also present other applications.   

Live

\normalsize \indent The search for exotic hybrid mesons is the primary goal of the GlueX experiment at Jefferson Lab. Possible decays of the $\eta_{1}$ and $b_{2}$ exotic hybrid mesons could occur through the $a^{\pm}_2(1320)\pi^{\mp}$, $f_2(1270)\eta$, and $\rho\eta$ intermediate states, where all of these can be detected in the $\eta\pi^{+}\pi^{-}$ final state. We will report on the reaction $\gamma p\to p\eta\pi^{+}\pi^{-}$ using $9$~GeV linearly polarized photons in GlueX. Evidence for the $a_{2}\pi$, $f_{2}\eta$ and $\rho\eta$ intermediate states will be presented. We will also discuss other contributions to this final state and the path forward to the full analysis of this final state in GlueX.