Strings,bags, and baryoniums

We show that (i) a certain type of qq$\text{qq}$ states (M-diquoniums) have suppressed decays not only into mesons and B$\text{B}$, but also in cascade modes, (ii) the naive string picture can be misleading for multiquark systems in general.     

On quark molecules

The nonrelativistic quark model with three triplets and an octet of coloured gluons is examined. The interaction energy corresponding to certain quark molecules is calculated. It is shown that systems of $\text{qq}\text{qq}$ and $\text{qqqq}\text{q}$ are more strongly bound than $\text{q}\text{q}$ and qqq. Thus in order for the model to be valid there must exist exotic particles.     

Baryonium states in multiquark spectroscopy

The spectrum of qq$\text{qq}$ states, examined in a quark-gluon model combined with dual unitarization, yields two types of baryoniums both of which have narrow widths into mesons. One type has normal hadronic widths ～ 100 MeV into B$\text{B}$. The other is narrow, ～ 10 MeV, and goes into B$\text{B}$ only reluctantly, preferring, if possible, to decay by cascade, and, being a consequence only of hidden colour, is an important object to verify experimentally.     

Baryonium and the four-body problem

A stochastic variational method is used to solve the Schrödinger equation for the non-relativistic $\text{qq}\text{q}\text{q}$ system. The quarks are considered as interacting with the two-body one-gluon exchange potential and a linear four-body confining potential. The mass spectrum for the non-strange baryonium states is predicted, and a preliminary estimate made for the strength of the coupling of M-baryonium states to T-baryonium. The stability of baryonium states with respect to decay into mesons is investigated.     

O(18) revived: Splitting the spinor

We propose an O(18) theory which is perturbatively unifiable and which accounts for the absence of right-handed families in the low-energy world. The theory predicts a fourth left-handed family as well as four right-handed families at energies near the weak scale. It also implies the existence of eight light neutrinos, all of which contribute to the width of the Z⁰. Cosmological arguments suggest that four of these neutrinos should have masses between 2 and 35 GeV, and that the other four should be much lighter. They also suggest the existence of a doubly charged scalar φ⁺⁺ and a singly charged scalar φ⁺. Dramatic signatures include the production of four right-handed charged leptons and eight right-handed quarks, $\text{Z}{}^0\text{→ v′}{}_{\mathrm{<mtext>R</mtext>}}\text{+}\text{v}\text{′}{}_{\mathrm{<mtext>R</mtext>}}\text{→ v}{}_{\mathrm{<mtext>R</mtext>}}\text{γ +\_}\text{v}{}_{\mathrm{<mtext>R</mtext>}}\text{γ}$, and e⁺e^? → φ⁺⁺ + φ^??. The lightest right-handed charged quark should be surprinsingly long-lived $\text{(τ?10}{}^{\mathrm{?2}}\text{sec}\text{)}$ for a particle of mass ? 100 GeV.     

A calculation of Z0 → 2 gluinos

We report the results of a one-loop calculation of $\text{Z}{}^0\text{→}\text{gg}$, where $\text{g}$ is a gluino, the proposed supersymmetric partner of a gluon. Depending on the masses of the scalar quarks and of the top quark, the branching ratio for the decay is in the 10^?5 to 10^?4 range for gluino mass below about 40 GeV. The signature for gluinos should allow detection in this range.     

A search for massive photinos at petra

We have searched for the supersymmetric partner of the photon, the photino, by investigating two-photon and single photon final states in e⁺e^? collisions. No significant signals were observed, which excludes the existence of the photino in the mass range 0.08–18 GeV/c² at the 95% confidence level, subject to the assumptions d=(100 GeV)² and $\text{m}{}_{\mathrm{<mtext>e</mtext><mtext>?</mtext>}}\text{=40}\text{GeV}\text{/c}{}^2$, where d is the supersymmetry breaking scale parameter and $\text{m}{}_{\mathrm{<mtext>e</mtext><mtext>?</mtext>}}$ is the scalar electron mass.     

Scalar mesons and the iota: A paradox explained

We show that the “δ(980) dominance” of the decay ι(1440)→ K$\text{K}$π, apparently contradicting the failure to observe the decay ι→ ηππ, can be explained in the K$\text{K}$ molecule interpretation of the S¹ and δ scalar mesons as an effect of K$\text{K}$ final state interactions.     

A relativistic quark model for mesons based on numerical solutions of the Bethe-Salpeter equation

A study is made to determine if the results of the nonrelativistic quark model can be reproduced by a fully relativistic model of deeply bound $\text{spin}\text{-}\text{1}\text{2}$ quarks. It is found that the relativistic model does not reproduce the nonrelativistic results, even when the quarks have nonrelativistic momenta. However, the model is rather successful in accounting for the known properties of mesons.Numerical solutions to the Bethe-Salpeter equation are obtained for pseudoscalar and vector bound states of equal mass quark-antiquark pairs, with either a scalar, pseudoscalar, or neutral vector exchange interaction. The interaction function corresponds to single particle exchange, with the addition of either one or two regulating terms. It is found that the second regulator allows the internal quark momentum to be nonrelativistic, but that the spinor structure of the wave function remains highly relativistic.Only the scalar interaction can account for the observed spectrum of states. The pseudoscalar interaction yields a vector state of lower mass than the pseudoscalar state, and the vector interaction leads to a vector state which lies approximately one quark mass above the pseudoscalar state. The λ quark is taken as slightly heavier than the p and n, and the perturbation treatment of the mass difference leads to a quadratic mass formula.The decay amplitudes for π, K → μν are calculated, and it is found, independent of parameters, that $\text{?}{}_{\mathrm{\pi }}\text{≈ ?}{}_{\mathrm{K}}$ for either a scalar or vector interaction, in agreement with experiment and in contrast with the nonrelativistic model. The amplitudes for ?^o, ω, φ → e⁺e^?, μ⁺μ^? are also calculated, but in this case the ratios (again parameter independent) are in minor discrepancy with experiment.The question of the additivity of quark amplitudes is examined by calculating (with significant restrictions) the magnetic moments of the vector mesons and the amplitudes for magnetic transitions such as ω → π^oγ. The magnetic moments of the vector mesons have the same (trivial) ratios to each other as in the nonrelativistic model, but they are strongly enhanced over the sum of the quark magnetic moments. The amplitude for magnetic transitions, however, is related to the quark magnetic moments in approximately the same ratio as in the nonrelativistic model.The model is also used to obtain parameter dependent predictions for the masses and decay amplitudes. These predictions are not experimentally correct, but are generally well within an order of magnitude for a wide range of the parameters.The most significant defect discovered of the model is the presence of ghost states (the daughters of the vector mesons, with J^PC = 0^+?) with masses of about 2 BeV.     

The charged scalar-graviton coupling to order α

The electrodynamical corrections of order α to the charged scalar-graviton vertex are calculated in quantum field theory using the improved energy-momentum tensor. It is found that the deviations from Newton's law are of the r^?2 type, exactly the same as for the spin-$\text{1}\text{2}$ case. Also, the trace of the energy-momentum tensor is found not to vanish, at the one-loop level, in the limit of zero-mass scalar particles.     

τ → δν decay induced by light quark mass difference

The decay constant of scalar δ^±(980) induced by up and down quark mass difference is determined to be $\text{?}{}_{\mathrm{\delta }}{}^{\mathrm{<mtext>I</mtext>}}\text{= 2.1}\text{MeV}$ and hence BR(τ → δν) = 1.6 × 10^?5. A detection of a significantly larger branching ratio would imply non-conser vation of the vector current.     

Is there evidence for gluonium states from the J/ψ radiative decays?

It is shown how perturbative QCD at lowest order can be successfully compared with the data for the inclusive J/ψ radiative decays. Our interpretation of the observed γ spectrum allows us to rule out the possibility of gluons having an effective mass and leads to the prediction that the observed E(1440) object has spin 0^?. In the 0⁺ sector, glueballs around 1 GeV may contribute, as well as ? and S¹ resonances. More accurate data on $\text{ππ,}\text{K}\text{K}\text{and}\text{ηη}$ channels would allow one to distinguish between these two possibilities for a 0⁺ signal which is definitely required by the model.     

A model for baryonium

The spectrum of $\text{qq}\text{q}\text{q}$ hadrons examined in a quark-gluon model yields two types of state both of which have small mesonic widths and may be associated with baryoniums. One type (T-diquonium) has normal hadronic widths into $\text{B}\text{B}$, while other (M-diquonium) is narrow and decays into $\text{B}\text{B}$ only reluctantly, preferring if possible to decay by cascade. The experience gained from ordinary hadron spectroscopy, plus some new phenomenological observations, allow one to predict the spectrum and properties of both types in considerable detail. The result bears close resemblance to present experiment.The existence of narrow M-diquonium states follows only from hidden colour, and if established would be a major triumph for the concept. It would be, however, only the first example of a quite general phenomenon which may well develop into a whole new branch of hadron spectroscopy.     

Two-loop renormalization group equations in a general quantum field theory: (III). Scalar quartic couplings

The two-loop β-functions for the scalar quartic couplings are computed in a general renormalizable quantum field theory with scalar, $\text{spin}\text{-}\text{1}\text{2}$, and (vector) gauge fields associated with a general gauge group G, using dimensional regularization and modified minimal subtraction (^?MS). A more explicit form is given for the two-loop β-function of the quartic coupling of the Higgs doublet in the minimal QCD electroweak theory based on SU(3) × SU(2) × U(1).     

Yang-Mills instantons and the S-matrix

We present a scheme for calculating gauge-invariant S-matrix elements in the presence of instantons. We exploit the conformal invariance of the zero-mass field equations. The asymptotic in and out states are defined by their values on null infinity $\text{J}$. We use this method to calculate to lowest-order S-matrix elements for scalar particles and fermions in a dilute gas of SU(2) instantons and anti-instantons. The scalar particles acquire an effective mass and an effective interaction of the form $\text{exp}\text{(?(?}{}^2\text{/16π) ?}\text{?}\text{)}$, where ? is the scale of the instanton, plus other interactions which cannot be presented by a local effective lagrangian. The fermions acquire the effective lagrangian obtained by 't Hooft. In the case of a single flavour of fermions, this corresponds to a mass term.