Heavy quark symmetry in quark models

Abstract

We study the heavy quark symmetry with the homogeneous bag model (HBM) and lightfront quark model (LFQM) based on the decays of Λ 0 b → Λ + c ℓ − ν ℓ (ℓ = e, µ, τ ). In particular, we calculate various parameters in the heavy quark expansions, including the Isgur-Wise functions and their first order corrections. The parameters in the HBM are fitted from the mass spectra, while the ones in the LFQM are tightly constrained by the heavy quark symmetry, granting the predictive power of our results. We explicitly obtain that B(Λ 0 b → Λ + c e − ν e ) = (5.69 ± 0.58, 5.35 ± 0.50), B(Λ 0 b → Λ + c µ − ν µ ) = (5.67 ± 0.58, 5.33 ± 0.49), and3243 ± 0.0126, 0.3506 ± 0.0046) for the numerical values of (HBM, LFQM). Our results of the branching fractions in both models agree well with the experimental data and lattice QCD calculations. In addition, we find that the hard gluon corrections decrease the branching fractions around 10%.

Study of singly heavy baryon lifetimes

“…The readers who are interested in the interplay between mass corrections and matrix elements are referred to ref. [28]. On the other hand, by an explicit calculation, we find that the CMM will in general decrease λ 2 around 10% for a fixed α s .…”

“…[23,24] by substituting Λ QCD = 0.33 GeV for E q . 8 The choice of E u,d = 0.32 GeV was proved to be suitable in describing the exclusive semileptonic decays of heavy baryons [28,31].…”