${\Lambda }_b\to p$ transition form factors in perturbative QCD

Abstract

We reanalyze the ${\Lambda }_b\to p$ transition form factors in the perturbative QCD (PQCD) approach by including higher-twist light-cone distribution amplitudes (LCDAs) of a ${\Lambda }_b$ baryon and a proton. The previous PQCD evaluation performed decades ago with only the leading-twist ${\Lambda }_b$ baryon and proton LCDAs gave the form factors, which are two orders of magnitude smaller than indicated by experimental data. We find that the twist-4 ${\Lambda }_b$ baryon LCDAs and the twist-4 and -5 proton LCDAs contribute dominantly, and the enhanced form factors become consistent with those from lattice QCD and other nonperturbative methods. The estimated branching ratios of the semileptonic decays ${\Lambda }_b\to p\ell {\bar{\nu }}_{\ell }$ and the hadronic decay ${\Lambda }_b\to p\pi$ are also close to the data. It implies that the $b$ quark mass is not really heavy enough, and higher-power contributions play a crucial role, similar to the observation made in analyses of $B$ meson transition form factors. With the formalism established in this work, we are ready to study various exclusive heavy baryon decays systematically in the PQCD approach.

37 pages, 7 figures, version to be published in Eur.Phys.J.C

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• CP Violation of Baryon Decays with $N\pi$ Scatterings
• Estimates of exchange topological contributions and $CP$-violating observables in ${\Lambda }_b\to \Lambda \varphi$ decay
• Baryons in the light-front approach: The three-quark picture
• Observation of $D^{+}\to K_S^0{a}_0(980{)}^{+}$ in the amplitude analysis of $D^{+}\to K_S^0{\pi }^{+}\eta$
• Light Cone Distribution Amplitude for the $\Lambda$ Baryon from Lattice QCD
• Charmonium decays of beauty baryons in the perturbative QCD approach
• Higher twist corrections to doubly-charmed baryonic $B$ decays
• Final-state rescattering mechanism in bottom-baryon decays
• Mixing effects of $\eta -{\eta }^{\prime }$ in ${\Lambda }_b\to \Lambda {\eta }^{{(}^{\prime })}$ decays
• Form factors of ${\Lambda }_b^0\to {\Lambda }_c(2595{)}^{+}$ within light-cone QCD sum rules
• Estimates of the isospin-violating ${\Lambda }_b\to {\Sigma }^0\varphi ,{\Sigma }^{0}J/\psi$ decays and the $\Sigma -\Lambda$ mixing
• $U$-spin sum rules for two-body decays of bottom baryons