Hadron Physics Seminar

Baryons at BESIII

by Dr. Beijiang Liu (Institute for High Energy Physics (IHEP)(IHEPPeking))

Wednesday, June 7, 2017 from to (Europe/Berlin)
at GSI ( Main auditorium (SB) )
Baryons are the basic building blocks of our world. Since baryons represent the simplest system in which the three colors of QCD neutralize into colorless objects and the essential non-Abelian character of QCD is
manifest, understanding the baryon structure is absolutely necessary before we claim that we really understand QCD. Given many recent processes, our present baryon spectroscopy is still in its infancy. Many fundamental issues in baryon spectroscopy are still not well understood. The possibility of new, as yet unappreciated, symmetries could be addressed with accumulation of more data. In addition to baryons made of u and d quarks, the search for hyperon resonances remains an important challenge. Some of the lowest excitation resonances are even missing, which are necessary to establish the spectral pattern of hyperon resonances.

Charmonium decays provide an excellent place for studying excited nucleons and hyperons -- $N^*$, $\Lambda^*$, $\Sigma^*$ and $\Xi^*$ resonances. Complementary to other facilities, the baryon program at BES3 has several advantages~\cite{Zou:2001uc}. For instance, $\pi N$ and $\pi\pi N$ systems from $J/\psi\to\bar NN\pi$ and $\bar NN\pi\pi$ processes have an isospin of 1/2 due to isospin conservation; $\psi$ mesons decay to baryon-antibaryon pairs through three or more gluons, where is a favorable place for producing hybrid (qqqg) baryons, and for searching some "missing" $N^*$ resonances which have weak coupling to both $\pi N$ and $\gamma N$, but stronger coupling to $g^3N$. Recent results in baryon spectroscopy at BESIII will be presented. Physics Synergies between BESIII and PANDA will be also discussed. The cross section of charmonium(-like) states production $p\bar{p}\to X_{c\bar{c}} + Meson(s)$ at PANDA can be inferred from high precision studies of $ X_{c\bar{c}} \to p\bar{p} M$ at BESIII. There're further potentials for cooperation in the studies of hyperons and the development of PWA tools.