Electromagnetic Form Factors of Σ Hyperons

Electromagnetic form factors (EMFFs) are fundamental observable of baryons that intimately related to their internal structure and dynamics, where the EMFFs of hyperons provide valuable insight into the behavior of the strangeness. The EMFFs of hyperons can also help to understand those of nucleons as they are connected with the flavor SU(3) symmetry. The EMFFs of nucleons can be measured in both spacelike and timelike regions. However, it is difficult to probe the EMFFs of hyperons in spacelike region due to the unstable nature of hyperons. By means of electron-positron annihilation, the EMFFs of hyperons in timelike region is accessible via the production of hyperon-antihyperon pair. The timelike EMFFs of the isospin triplet Σ hyperons measured at Babar, CLEO-c and BESIII experiments are reviewed in this paper. Besides, the relevant theoretical discussion based on the experimental results are also presented.

HIGH SPIN ISOBARIC ANALOGUE STATES

The energy difference between members of the Pairing Triplet could be understood in the framework of charge independence. In the case of two-nucleon analogue stretched states, an estimation more refined than the addition rule is suggested to calculate the energy of pn or 2p states when the energy of 2n states is known. εc, defined as the difference between the residual energies of 2n and 2p states, could be interpreted as the Coulomb interaction between the two protons of the pair. The mean distances between the two nucleons, coupled to their minimum spin value and to their maximum spin value, could then be deduced illustrating the Pauli principle. Mirror members of an isospin triplet have similar lifetime and branching ratios, while the Tz=0 member has quite different properties due to the nonconservation of isospin in electromagnetic interaction. The [Formula: see text] state of the Tz=0 nuclei should decay through M1 transition of about 3 MeV to the [Formula: see text] state, and should have a short lifetime of about 1 fs. Charge independence could be tested by populating high-spin two-nucleon stretched states with 36Ar as the projectile. Proton-rich beam would be of interest to form mirror compound nucleus. Both compound nucleus and mirror compound nucleus would preferentially evaporate protons.