The charge form factor of three-nucleon systems and the polarization of the bound nucleon

Ernest Henley and the shape of baryons

“…During my stay in Seattle in 1999, Ernest and I discussed how to extract from the measured N → ∆ transition quadrupole moment the proton's intrinsic quadrupole moment, which contains the relevant information on the proton shape. We had noticed that most work that addressed the issue of nucleon deformation [23][24][25][26][27] did not clearly distinguish between intrinsic (bodyfixed frame) and the measured spectroscopic (laboratory) quadrupole moment as qualitatively shown in Fig. 3.…”

Intrinsic quadrupole moment of the nucleon

“…Even with respect to the sign of the intrinsic nucleon deformation there is no consensus. For example, references [8,9,10] conclude that the nucleon is oblate, while references [11,12,13] find a pro-late nucleon deformation. Several authors speak only about 'deformation' without specifying the sign.…”

Quadrupole moments of low lying baryons with spin 1/2^+, spin 3/2^+, and spin 3/2^+ \to 1/2^+ transitions

“…( 19) and ( 20) for each quark in Eqs. ( 10) and (11). The quadrupole moment of ∆ + and Ξ * − in χCQM can be expressed as…”

“…However, there is little consensus between the results even with respect to the sign of the nucleon deformation. Some of the models predict the deformation in nucleon as oblate [11], some predict a prolate nucleon deformation [12,13] whereas others speak about "deformation" without specifying the sign. It is important to mention here that the deformation of the octet baryons is an intrinsic phenomena and has to be coupled with the orbital angular momentum to compare with the spectroscopic value.…”