On photoexcitation of baryon antidecuplet

We show that the photoexcitation of the baryon antidecuplet, suggested by the soliton classification of low-lying baryons, is strongly suppressed on the proton target. The process occurs mostly on the neutron target. This qualitative prediction can be useful in identifying the non-exotic members of the antidecuplet in the known baryon spectrum. We also analyze the interrelation between photocouplings of various baryon multiplets in the soliton picture and in the nonrelativistic quark model. 1. The soliton picture of baryons suggests a certain classification scheme for the lowlying baryons. In this scheme various baryons appear as rotational excitations of the same classical object – soliton. In the case of three light flavours, the first two low-lying SUfl(3) multiplets are the octet and the decuplet, just the same as in the quark model and in reality. The third rotational excitation is an antidecuplet with spin 1/2. Probably the existence of the antidecuplet as the next SUfl(3) rotational excitation has been first pointed out at the ITEP Winter School (February, 1984), see Ref. [1]. Other early references for the antidecuplet include Refs. [2, 3, 4]. In Fig. 1 we draw the SUfl(3) diagram (from Ref. [5]) for the suggested antidecuplet in the (T3, Y ) axes, indicating its naive quark content as well as the (octet baryon + octet meson) content. In addition to the lightest Z, there is an exotic quadruplet of S = −2 baryons (we call them Ξ3/2). In Ref. [5] the following mass formula for the members of the antidecuplet was obtained: