SU(3) breaking in the two-body decays of the Ψ(3100)

Motivated by the experimental fact that the ψ(3100) does not appear to behave like an SU(3) singlet when it decays into a vector pseudoscalar final state, we propose a model for SU(3) breaking in ψ decays. In the model we envision the ψ decay as a two-stage'process. In the first stage the quark-antiquark pair which comprises the ψ annihilate via a Zweig rule violating interaction to create a pair of “ordinary” quarks. We allow this interaction to violate SU(3) invariance so that all quarks may not be created equally. In stage two the quark pair turns itself into hadrons via a Zweig-allowed, SU(3)-invariant interaction. The data for the vector-pseudoscalar decays seem to indicate that the intermediate quark pair behaves like a heavy ω. We then use this “fact”. to make predictions for the baryon-antibaryon and the tensor-vector decays.     

The meson electromagnetic decays from SU(4)W and generalized vector dominance

Using SU(4)_W and generalized vector dominance (GVD) we express the electromagnetic meson decays in terms of the pion form factor. Ordinary VMD seems adequate for one photon processes. Data indicate that U(3) is better in the constituent than in the current quark frame.     

Quark loop model of radiative meson decays

Radiative meson decays are computed from quark loop anomalies, taking into account the SU(3) splitting of the quark masses. Predicted rates for ?→ηγ,K ^*→Kγ, and η→ππγ are brought into satisfactory agreement with experiment. Formulas are given for the radiative decay rates of charmed las are given for the radiative decay rates of charmed mesons, and a mechanism suggested for suppression of the radiative decays of mesons containing a charmed quark.     

Four-fermion quark decays

Four-fermion weak decays of free quarks are considered in the case of broken SU(4) symmetry. Beta-type decays of quarks into leptons are investigated, and _c - 8.38·10^–15 sec is obtained for the charmed quark. Weak decays of quarks into baryons in the case of SU(4) symmetry are also investigated.Translated from Ivestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 18–23, August, 1980.     

Proton and neutron decay rates in conventional and supersymmetric guts

We present a general calculation of the two-body decay rates of the nucleon, for the most general form of four-fermion ΔB = ΔL operators, in the framework of the SU(6) non-relativistic quark model. We have applied our general formulas to Higgs mediated decays in conventional and in supersymmetric SU(5) models. Lower bounds upon the exchanged particles masses are given. We point out that the hierarchies of branching ratios in decays mediated by Higgs bosons are different from those of gauge boson decay modes (in the former case, neutrinos modes are dominant). We give, in conclusion, an experimental way to distinguish non-supersymmetric GUTs from supersymmetric ones, if the nucleon decays via Higgs bosons.     

Vector states in e+e− annihilation at 3.9–4.5 GeV

The structure observed at SPEAR in e⁺e^? annihilation in the energy range 3.9–4.5 GeV is explained in an SU(8) × SL(3, R) color quark model. The model can account for the mass differences, total hadronic and leptonic widths, as well as for the rise in, and the magnitude of, R. Main predictions are the SU(3) properties of these states, strong suppression of their decays into the ψ(3.1) and the existence of another vector meson around 6 GeV.     

Radiative decays,SU(4), and violations of the OZI rule

Radiative decays of old and new mesons are considered using SU(4) and vector dominance. Good agreement iis found for OZI-allowed decays, and a simple framework for studying OZI violations and their dependence on mass, angular momentum and quark type is established. A few assumptions about this dependence lead to quantitative and qualitative predictions which agree with existing experimental results. In addition, within the framework one can test the sufficiency both of mixing as a source of OZI violations and of the minimum number of gluons in $\text{q}\text{q}$ annihilations.     

Two body nonleptonic decays of Λb involving proton

We study some nonleptonic decays of Λ_b-baryon involving transition of a heavy to light quark, using nonrelativistic quark model for form factors. The decay rates for two such decays are consistent with the data available. Also these decays can give us information on the CKM matrix element |V_Ub|.     

The quark‐level linear σ model

This review of the quark‐level linear σ model (QLLσM) is based upon the dynamical realization of the pseudoscalar and scalar mesons as a linear representation of SU(2)× SU(2) chiral symmetry, with the symmetry weakly broken by current quark masses. In its simplest SU(2) incarnation, with two non‐strange quark flavors and three colors, this nonperturbative theory, which can be selfconsistently bootstrapped in loop order, is shown to accurately reproduce a host of low‐energy observables with only one parameter, namely the pion decay constant f_π. Extending the scheme to SU(3) by including the strange quark, equally good results are obtained for many strong, electromagnetic, and weak processes just with two extra constants, viz. f_K and <π |H_weak|K>. Links are made with the vector‐meson‐dominance model, the BCS theory of superconductivity, and chiral‐symmetry restoration at high temperature. Finally, these ideas are cautiously generalized to the electroweak sector, including the W, Z, and Higgs bosons, and also to CP violation.     

Charmless hadronic decays of B mesons to a pseudoscalar and a tensor meson

We study two-body charmless hadronic decays of B mesons to a pseudoscalar meson (P) and a tensor meson (T) in the frameworks of both flavor SU(3) symmetry and generalized factorization. Certain ways to test the validity of the generalized factorization are proposed, based on the flavor SU(3) analysis. We present a set of relations between a flavor SU(3) amplitude and the corresponding amplitude in the generalized factorization which bridge both approaches in decays. The branching ratios and CP asymmetries are calculated using the full effective Hamiltonian including all the penguin operators and the form factors obtained in the non-relativistic quark model of Isgur, Scora, Grinstein and Wise. We identify the decay modes in which the branching ratios and CP asymmetries are expected to be relatively large. Received: 6 July 2001 / Revised version: 8 October 2001 / Published online: 30 November 2001     

The existence of the t-quark and its relation to decays of the B mesons

We construct the general five quark model in SU(2) × U(1) and study its phenomenological consequences, in particular its predictions for B states. The model is consistent with experiments and we estimate semileptonic decays that distinguish it from the sequential model.     

Flavor symmetry,EMC results and the spin content of the proton

The analysis of the EMC result on the quark contribution to the spin of the proton has caused considerable confusion and is unnecessarily complicated because of the completely unjustified and incorrect use of SU(3) flavor symmetry to provide input on the proton wave function from hyperon decays. There is no reliable method for obtaining information on the proton spin structure from data on the couplings of currents to hyperons. Interesting peculiar results obtained without use of SU(3) and hyperon data show the crucial point to be the apparent contradiction between the contribution of valence u quarks to the proton spin observed in the axial vector contribution to nucleon beta decay and the failure of this contribution to appear in the conventional quark-parton interpretation of the EMC results. When input from hyperon data is not used this paradox can be resolved without requiring the quark contribution to the proton spin to be near zero, but it can be large only if it is due to the strange quarks, with the nonstrange quark contribution opposite to the spin of the proton.     

Higgs bosons in supersymmetric models (III). Decays into neutralinos and charginos

We give explicit formulae for the decays of the Higgs bosons of the minimal supersymmetric model to neutralinos and charginos. The important features of these decays are illustrated and their phenomenological implications discussed. Particular attention is given to the decays of heavy Higgs bosons (with masses larger than m_Z) which can only be observed at a future supercollider. When phase-space allowed, Higgs decays into neutralinos and charginos are at least as important as, and often dominate, other types of Higgs decay modes, such as WW, ZZ, and heavy quark (or lepton) pairs.     

Prospects for superstring models with two vacuum expectation values for standard model singlets

The spontaneous breaking of rank-six intermediate groups to the standard model in superstring phenomenology is examined. It requires the existence of two vacuum expectation values, one for each standard model singlet in the 27 chiral representation of E₆. We use a simplified model based on the group SU(3)_c×SU(2)_L×SU(2)_R×U(1)_L×U(1)_R. It is found that the well-known phenomenological constraints such as proton decay, vanishing neutrino masses and flavour-changing neutral currents allow for the possibility of sizeable Yukawa couplings for the two standard model singlets which can originate low energy negative masses. The proof of this radiative breaking relies, however, on several parameters whose magnitude is unpredicted, but is facilitated if the mass of the exotic quark is large (∼300 GeV).     

Semileptonic decays of heavy quarks in quantum chromodynamics

We investigate the semileptonic decays of heavy quarks in the leading non-trivial order in quantum chromodynamics. Effects of gluon corrections and the initial quark Fermi motion on the semileptonic rates and decay distributions are calculated. The resulting lepton energy spectrum for the charm semileptonic decay is compared with data to extract the mass of the charm quark. This is combined with the semileptonic branching ratio to predict the charm-quark lifetime. We find the lepton energy spectrum very stable with respect to gluon corrections. Expected spectra from the semileptonic decays of bottom and top quarks are presented. We also study the semileptonic decay process Q → q?v_? + G, involving the emission of a single hard non-collinear gluon. This process should be observable with a branching ratio of a few percent in the decays of top (and heavier) quarks.     

HYPERON DECAYS IN THE CNIRAL BAG MODEL

In terms of the chiral bag model and SD(3) Skyrme wave-functions of baruons, we investigate Δ⁺ →Pγ (SU(2)) and Σp⁺ → Pπ⁰ (SU(3) case) hyperon decays. We have found that for Δ⁺ →Pγ the Skyrme contribution is more important whereas in Σp⁺ → Pπ⁰ the quark content transition dominates.     

Representation mixing and the ideal description of mesons

Representation mixing of meson states is considered with particular reference to the 1 ←→ 15 mixing in SU(4). The 16 meson states are assigned to the representation (4*, 4) of a non-chiral group SU(4) ? SU(4), whose factors are related by charge-conjugation. Mass formula, mixing angles and electromagnetic mass shifts are rigorously derived. Connection of the present formalism with conventional quark model is pointed out and generalisations to higher groups SU(n) ? SU(n) as well as to higher representations, are indicated.     

VMD, the WZW Lagrangian and ChPT: The third mixing angle

We show that the Hidden Local Symmetry Model, supplemented with well-known procedures for breaking flavor SU(3) and nonet symmetry, provides all the information contained in the standard Chiral Perturbation Theory (ChPT) Lagrangian . This allows to rely on radiative decays of light mesons ( and ) in order to extract some numerical information of relevance to ChPT: a value for , a quark mass ratio of , and a negligible departure from the Gell-Mann–Okubo mass formula. The mixing angles are and . We also give the values of all decay constants. It is shown that the common mixing pattern with one mixing angle is actually quite appropriate and algebraically related to the mixing pattern presently preferred by the ChPT community. For instance the traditional is functionally related to the ChPT and fulfills . The vanishing of , supported by all data on radiative decays, gives a novel relation between mixing angles and the violation of nonet symmetry in the pseudoscalar sector. Finally, it is shown that the interplay of nonet symmetry breaking through U(3) SU(3) U(1) satisfies all requirements of the physics of radiative decays without any need for additional glueballs. Received: 20 June 2000 / Published online: 23 October 2000     

Implications of a natural fermion mass hierarchy

The hierarchical struture of the fundamental fermion mass spectra is required to arise in a non-accidental way from a unified model G_family with a horizontal symmetry factor group G_generation. A quark or lepton must then not be in the same representation of G_family as its anti-particle. Models for G_family of the type SU(4)_C × SU(2)_L × SU(2)_R are favoured over SU(5) or SO(10).