Charmed Baryon Strong Coupling Constants in a Light-Front Quark Model

Light-Front quark model spin wave functions are employed to calculate the three independent couplings gΣcΛcπ, fΛc1Σcπ and fΛc1Σcπ of S-wave to S-wave and P-wave to S-wave one-pion transitions. It is found that gΣcΛcπ = 6.81 MeV , fΛc1Σcπ = 1.16 and fΛc1Σcπ = 0.96 × 10−4 MeV. We also predict decay rates for specific strong transitions of charmed baryons. In the heavy quark limit, the spin and parity of the heavy quark and light degrees of freedom are separately conserved in the hadron. In addition, strong and electromagnetic transitions among heavy baryon states are transitions solely of the light quark system. Therefore, heavy quark symmetry when supplemented by light flavour symmetries, such as SU(2) or SU(3) symmetry, relate these decays. Explicit relations between the various decay couplings of heavy baryons were derived in the constituent quark model [1, 2]. S-wave to S-wave heavy baryon strong decays, for instance, are determined by a single coupling constant and two independent couplings are required to describe single pion transitions from P-wave to S-wave states. The coupling gΣcΛcπ determines strong decays among charmed baryon ground states. Furthermore, single pion transitions from the first excited states into ground state are described in terms of two couplings fΛc1Σcπ and fΛc1Σcπ. The Λc1 and Λ ∗ c1 represent the two excited states discovered recently [3] with masses 2593 MeV and 2625 MeV respectively. In a heavy baryon, a light diquark system with quantum numbers j couples with a heavy quark with J Q = 1/2 + to form a doublet with J = (j±1/2). Heavy quark symmetry allows us to write down a general form for the heavy baryon spin wave functions (s.w.f.) [1, 4] χαβγ = (φμ1···μj )αβψ μ1...μj γ (v) . (1) Here, vμ = Pμ M is the baryon four velocity, the spinor indices 1 α and β refer to the light quark system and the index γ refers to the heavy quark. The number of the Lorentz indices μj is determined by the light diquark system quantum number j and is equal to 0, 1 and 2 for S-wave and P-wave baryon states. In the heavy quark limit, the χαβγ satisfy the Bargmann-Wigner equation on the heavy quark index, (6v) ′ γ χαβγ′ = χαβγ . (2) We have ignored the isospin indices which will be included in the transition amplitudes later on.