Baryon wave functions and nucleon decay

Pramana, 1996

The decay widths for the radiative decays of heavy baryons are calculated in the heavy quark effective theory. Introducing the interpolating fields for heavy baryons we obtain the transition matrix elements and the corresponding decay widths. Considering the SU(6) flavor-spin wave functions for heavy baryons, the coupling constants are calculated in the nonrelativistic quark model. Since the masses of the heavy baryons are not available, we have taken the predicted bag model masses. We find our results are quite different from that of the heavy quark bag model calculations.

We discuss various topics in the theory of heavy baryon decays. Among these are recent applications of the Relativistic Three Quark Model to semileptonic, non-leptonic, one-pion and one-photon transitions among heavy baryons, new higher order perturbative results on the correlator of two heavy baryon currents and on the semi-inclusive decay Λ b → X c + D

1991

Weak electric and magnetic form factors for semileptonic baryon decays are calculated in a relativistic quark model based on the Dirac equation with the independentquark confining potential of the form V¢(r)= ½(1 + y°)(aer + Vo). The values obtained for (gz/01) are not very much different from the nonrelativistic results of Donoghue and Holstein. The values of (gl/fl)extracted from our model calculations of (f2/fl) in the Cabibbo limit compare well with the experimental values. The values of (f2/ft) for various semileptonic transitions are also estimated incorporating phenomenologically the effect of nonzero 02 in the ratio (g~/fl). It is found that the SU (3)-symmetry breaking does not generate significant departui'es in (fzffl) values from the corresponding Cabibbo predictions.

Progress of Theoretical Physics, 1977

Non-leptonic weak decays of hyperons and of charmed baryons are investigated within the framework of SU(S) and SU(S)w on the assumption that weak interaction is of the current® current form (the currents being of the GIM type) and is CP invariant. We find that SU(S) conveys more information about pv decays than SU(4). Several relations in addition to the ones obtained in SU(4) are obtained. The assumption of 20"-dominance at the SU(4) level is no longer required for the pv decays of the hyperons. Unlike in SU(6)w we are able to get the Lee-Sugawara sum rule for pc decays in SU (8) w without being forced to take ~!=0. § I. Introduction Non-leptonic weak decays of Hyperons!) and of charmed particles 2 > have been discussed on the basis of SU(4) symmetry. On the basis of the idea of spin-unitary

A new analysis of hyperon semi-leptonic decay data is presented, based on simple and general arguments for an SU(3)-breaking structure of the couplings involved. The results obtained are compatible with those of earlier investigations and highlight the uncertainties inherent in extraction of the V us Cabibbo-Kobayashi-Maskawa matrix element from such data, and the need for complete analyses. For F and D, the results can be summarised by the ratio: F/D = 0.57 ± 0.01; while as far as the value of V us is concerned, the only conclusion to be drawn is that, insofar as SU(3) breaking is still not totally under control, the value obtained is compatible but not competitive with that obtained from kaon semileptonic decays.

Phys Rev D, 1999

QCD sum rules for the determination of form factors of $\Lambda_b$ and $\Lambda_c$ semileptonic decays are investigated. With a form for the baryonic current appropriate for the limits of the heavy quark symmetries, the different tensor structures occurring in the two- and three-point functions are separately studied, and in each case general relations are written for the form factors. Particular attention is given to the treatment of the kinematical region ascribed to the continuum. The $t$-dependence of the form factors and the decay rates are numerically evaluated and compared to experimental information.

Progress of Theoretical and Experimental Physics, 1977

We study the weak radiative decays of uncharmed and charmed baryons in the SU(4) and SU(S) symmetry framework. \Ve find that the GIM model of weak interactions gives unsatisfactory results for the weak radiative decays of uncharmed baryons, at SU(4) leveL An admixture of 15-dimensional representation of SU(4) in the GIM weak Hamiltonian is indicated. We propose measurement of the decay z->.s-r in order to elucidate the structure of the weak Hamiltonian. § 1. Introduction Weak radiative decays of hyperons have been discussed by several authors 11 in the domain of SU(3) symmetry. The available experimental information about these decays is meagre. Definite numbers have been reported for the process 2+-'>Pt only. We have 21 T(2~-'>Pt)_ = (1.43±0.26) X 10-3 r (2+->all) and the asymmetry parameter a for this decay is (-1.03:':UD. Even this small information about the weak radiative decays has been a source of considerable difficulty for the weak interaction phenomenology. In the current ~ current model of weak interactions, if one assumes the same behaviour under C (charge conjugation) for the parity violating (pv) and parity conserving (pc) parts of the weak Hamiltonian the asymmetry parameter for 2+ decay turns out to be zero. 11 A small negative value for a can be obtained in pole models by making certain assumptions about the intermediate states. 31 " 11 But a large value of a (2+->Pr) remains unexplained. A simple way out is to assume that the pv and pc parts of the weak Hamiltonian have opposite behaviour under C. This means that at the SU(3) level one assumes the pv Hamiltonian to transform as }., component of the octet and the pc Hamiltonian to transform as J.6 • This choice for the weak Hamiltonian has already been proposed in the context of quark-density model, 51 and has the attractive feature that K,->27r is not zero in the SU(3) limit. This SU(3) structure for the weak Hamiltonian is also obtained in recent models with right-handed currents. 61 With this assumption, both pv and pc parts of the weak Hamiltonian transform similarly under CP and the amplitude for S"-'>Pt is non-zero in both

Reviews of Modern Physics, 2012

A comprehensive overview of kaon decays is presented. The Standard Model predictions are discussed in detail, covering both the underlying short-distance electroweak dynamics and the important interplay of QCD at long distances. Chiral perturbation theory provides a universal framework for treating leptonic, semileptonic and nonleptonic decays including rare and radiative modes. All allowed decay modes with branching ratios of at least 10 −11 are analyzed. Some decays with even smaller rates are also included. Decays that are strictly forbidden in the Standard Model are not considered in this review. The present experimental status and the prospects for future improvements are reviewed.

Physical review D: Particles and fields, 1994

We study nonleptonic decays of the orbitally excited, SU(6) 70-plet baryons in order to test the hypothesis that the successes of the nonrelativistic quark model have a natural explanation in the large-N c limit of QCD. By working in a Hartree approximation, we isolate a specific set of operators that contribute to the observed s-and d-wave decays in leading order in 1/N c . We fit our results to the current experimental decay data, and make predictions for a number of allowed but unobserved modes.

Physical Review C, 2006

The semileptonic decays of Ωc and Ω b are treated in the framework of a constituent quark model developed in a previous paper on the semileptonic decays of heavy Λ baryons. Analytic results for the form factors for the decays to ground states and a number of excited states are evaluated. For Ω b to Ωc the form factors obtained are shown to satisfy the relations predicted at leading order in the heavy-quark effective theory at the non-recoil point. A modified fit of nonrelativistic and semirelativistic Hamiltonians generates configuration-mixed baryon wave functions from the known masses and the measured Λ + c → Λe + ν rate, with wave functions expanded in both harmonic oscillator and Sturmian bases. Decay rates of Ω b to pairs of ground and excited Ωc states related by heavy-quark symmetry calculated using these configuration-mixed wave functions are in the ratios expected from heavy-quark effective theory, to a good approximation. Our predictions for the semileptonic elastic branching fraction of ΩQ vary minimally within the models we use. We obtain an average value of (84± 2%) for the fraction of Ωc → Ξ (*) decays to ground states, and 91% for the fraction of Ωc → Ω (*) decays to the ground state Ω. The elastic fraction of Ω b → Ωc ranges from about 50% calculated with the two harmonic-oscillator models, to about 67% calculated with the two Sturmian models.