Factorization of Heavy-to-Light Baryonic Transitions in SCET

Abstract

In the framework of the soft-collinear effective theory, we demonstrate that the leading-power heavy-to-light baryonic form factors at large recoil obey the heavy quark and large energy symmetries. Symmetry breaking effects are suppressed by $\Lambda /m_b$ or $\Lambda /E$, where $\Lambda$ is the hadronic scale, $m_b$ is the $b$ quark mass and $E\sim m_b$ is the energy of light baryon in the final state. At leading order, the leading power baryonic form factor ${\xi }_{\Lambda ,p}(E)$, in which two hard-collinear gluons are exchanged in the baryon constituents, can factorize into the soft and collinear matrix elements convoluted with a hard-kernel of order ${\alpha }_s^2$. Including the energy release dependence, we derive the scaling law ${\xi }_{\Lambda ,p}(E)\sim {\Lambda }^2/E^2$. We also find that this form factor ${\xi }_{\Lambda }(E)$ is numerically smaller than the form factor governed by soft processes, although the latter is formally power-suppressed.

Comments: 18 pages, 2 figures, references and more discussions added; journal version