New Universality of Baryon Isgur--Wise Form Factor in the Large $N_c$ limit

Abstract

New universality appears for the baryon Isgur--Wise form factor in the large $N_c$ limit. It is found that the semileptonic ${\Lambda }_b\to {\Lambda }_c$ and ${\Sigma }_b^{(\ast )}\to {\Sigma }_c^{(\ast )}$ decays are described by the same form factor, which can be calculated analytically. In the exact chiral $SU(3)$ limit, the same form factor is applicable to semileptonic ${\Omega }_b^{(\ast )}\to {\Omega }_c^{(\ast )}$ decays.

Comments: 5 pages in REVTEX galley style, CALT-68-1946