b-baryon semi-tauonic decays in the Standard Model

Abstract

Within the framework of HQET, ${\Lambda }_b\to {\Lambda }_c\tau {\bar{\nu }}_{\tau }$ and ${\Omega }_b\to {\Omega }_c^{(\ast )}\tau {\bar{\nu }}_{\tau }$ weak decays are studied to the order of $1/m_c$ and $1/m_b$. Helicity amplitudes are written down. Relevant Isgur-Wise functions given by QCD sum rule and large $N_c$ methods are applied in the numerical analysis. The baryonic R-ratios $R({\Lambda }_c)$ and $R({\Omega }_c^{(\ast )})$ are obtained.

Comments: 20 pages, 7 figures and 1 table; v2: reference added