Light-Cone Distribution Amplitudes of Bottom Baryons

Abstract

The B-meson factories at SLAC and KEK, after approximately a decade of their operation, have made a great impact on a clarification of CP -violation origin in the quark sector of the Standard Model (SM). Study of heavy-light hadrons, in particular mesons and baryons containing the b-quark, at the LHC can serve as an additional test of the Kobayashi-Maskawa mechanism. Specific processes with bottom baryons, such as rare decays involving flavor-changing neutral currents (FCNC) transitions, are potential sources of new physics beyond the SM. In a difference to B-mesons, a non-zero spin of baryons allows also an experimental study of spin correlations. The spectrum of heavy bottom baryons have been enlarged substantially thanks to the effort done by the CDF and D0 Collaborations at the Tevatron collider and is presented in Table 1. During the LHC Run I, the majority of the bottom-baryon states has been confirmed and several new ones were observed. Unlike these progress, study of the FCNC motivated decays of bottom baryons remains to be statistically limited. A grater effort is expected during the next LHC run where heavy baryons will be copiously produced, and their weak decays may be measured precisely enough to provide important clues on physics beyond the Standard Model. The theory of bottom baryon decays into light hadrons is more complicated compared to the B-meson decays and, hence, was receiving less attention. Calculations of heavy-baryon decays into light particles based on the heavy quark expansion, see e. g. [1], or using sum rules of the type proposed in [2, 3, 4] require the primary non-perturbative objects — the distribution amplitudes of heavy baryons. For a long period, the only existed models of heavybaryon distribution amplitudes [5, 6] have been motivated by quark models and not consistent with QCD constraints. In the paper [7], the complete classification of three-quark light-cone distribution amplitudes (LCDAs) of the Λb-baryon in QCD in the heavy quark limit was given and the scale-dependence of the leading-twist LCDA is discussed. In addition, simple models of the LCDAs were suggested and their parameters were fixed based on estimates of the first few moments by the QCD sum rules method. The analysis of [7] has been extended on all the ground state b-baryons with the spin-parity both J = 1/2 and J = 3/2. The basic steps and main results of such an analysis are summarized in this lecture and all the details are presented in our papers [8, 9].