Broken SU Research Articles

Composite Higgs scalars

We construct models in which the Higgs doublet whose vacuum expectation breaks SU(2) × U(10 is a bound state of massive strongly interacting fermions. The couplings of the composite Higgs to ordinary fermions are induced by heavy gauge boson exchange in the manner of extended technicolor. Other heavy gauge bosons generate a negative mass term for the Higgs.

The quantum field theories associated with a “staggered” ice-type model

The Hubbard model, the massive Thirring model and the broken SU(2) massive fermion model of Bukhvostov and Lipatov are show to be the scaling limit and two cases of continuum limit of a non-trivial integrable “staggered” ice-type vertex model, recently solved by Bariev.

Baryon magnetic moments

We discuss the baryon magnetic moments using the chiral bag model. The pion cloud contributes significantly to the moments and we point out that pion-pion interactions which enhances this contribution together with an isoscalar part is sufficient to explain the deviation of the baryon magnetic moments from their broken SU(6) values.

Meson exchanges in the harmonic-oscillator quark model

Meson exchanges are introduced into the harmonic oscillator quark model along with a lower quark wave function. The mechanism is based on quark correlations that derive from quark exchange scattering via gluon exchange at short distances. This method allows avoiding spurious van der Waals forces at long range. Meson-baryon coupling constants and vertex form factors are calculated. They are found to be in agreement with those obtained from other quark models, phenomenological potentials, and the broken SU(3) flavor symmetry. The resulting $S$-wave NN phase shifts are compared with those from quark-molecular models.NUCLEAR REACTIONS Meson exchanges, ${E}_{\mathrm{lab}}\ensuremath{\le}300$ MeV. Coupling constants, vertex form factors calculated from harmonic-oscillator quark interchange model. Comparison of NN $S$-wave phase shifts with those of potential models.

Light singlet, gauge hierarchy and supergravity

The existence of light singlets to help the breaking of SU (2) × U (1) in supersymmetric grand unified theories destroys the gauge hierarchy. The phenomenon exists for both global and local SUSY-GUT models.

Chiral symmetry breaking and condensates in the rishon model

The rishon model is studied in the limit g c → 0, α → 0 when its global flavour symmetry is SU(6) × SU(6) × U(1) analogous to six massless flavour QCD. Recently it was shown that the ad hoc breaking SU(6) × SU(6) → SU(3) × SU(3) allows the anomaly constraint to be satisfied. In this paper this is shown to be but one of several successful patterns of chiral symmetry breaking. The condensates required to perform these breakings are fully discussed. A plausibility argument based on single gauge boson exchange is presented which determines the condensate uniquely to be 〈(v LV L) 3〉 corresponding to the original breaking above. The same argument applies to QCD, which is argued to differ in its chiral behaviour due to the large intrinsic masses of the quarks. The implications of the above condensate and pattern of chiral symmetry breaking for the rishon model include the prediction of integer charged colour octet fermions, a naive mass formula m e = 2 m u − m d, new insight into the parity-violating condensate 〈(v Lv L) 2(v Rv R)〉 and the prediction of 52 new pseudos whose masses are estimated.

Crossover from the strong-coupling to the weak-coupling regime in the SU(2)-symmetric Thirring model

Using the exact solution of the Thirring model with broken SU (2) symmetry we study a transition from the strong-coupling to the weak-coupling regime taking place on changing the anisotropy parameter.

Locally supersymmetric SU(5) grand unification

We consider the coupling of the SU(5) GUT to N = 1 supergravity. A general strategy to obtain a reasonable low-energy phenomenology is discussed. Very simple superpotentials naturally lead to large (∼ m p) vacuum expectation values for the Higgses breaking SU(5) but no large expectation values for the scalar quarks and leptons. Various schemes for obtaining naturally massless Higgs doublets are discussed. Local supersymmetry is broken at a scale ∼10 11 GeV and the weak interaction scale is generated from the soft terms breaking global supersymmetry which are left after the breakdown of supergravity. The 24-Higgs scalar potential is very flat and may have cosmological relevance.

Extrema of Higgs potentials and higher representations

The problem of symmetry breaking is studied. A method suitable for higher-rank tensors is suggested. This method is used to break SU(2n)..-->..SU(n) x SU(n) x U(1) via the traceless symmetric fourth-rank tensor T/sup opening-bracea/b)/sub opening-bracec/d).

Locally Supersymmetric Grand Unification

A locally supersymmetric grand unification program is proposed which couples the $N=1$ supergravity multiplet to an arbitrary grand unified gauge group with any number of left-handed chiral multiplets and a gauge vector multiplet. A specific model is discussed where it is shown that not only do the gravitational interactions eliminate the degeneracy of the vacuum state encountered in global supersymmetry, but simultaneously they can break both supersymmetry and SU(2) \ensuremath{\bigotimes} U(1) down to a residual $\mathrm{SU}{(3)}^{c}\ensuremath{\bigotimes}\mathrm{U}(1)$ symmetry at \ensuremath{\sim}300 GeV.

An SU(3)-based comparison between inclusive kaon and pion charge exchange scattering in the triple Regge region

We show that the SU(3) relation σ( K − p → K 0 X) = 0.5(σ(π − p → π 0 X) + 2.2σ (π − p → η X)) is approximately valid at high energy throughout the kinematic range, Feynman χ⩾0.7 and − t⩽1 (GeV/ c) 2, for the final stae particle. Our data are consistent with the usual SU(3) mixing of the η and η′. The breaking of SU(3) observed in our data corresponds in the Regge formalism to the ratio of the K K to ππ(η) couplings of the ϱ and A 2 trajectories being 14% larger than the SU(3) value.

Grand Unified Theories Based on Local Supersymmetry

General features are discussed of grand unified theories with local supersymmetry broken at high energies by the super-Higgs effect. The low-energy effective Lagrangian is a globally supersymmetric one with all the explicit soft breakings. It is argued that the energy splittings among the vacua due to gravitational effects must be small in order to be able to pick out the correct vacuum. Also discussed are the mechanisms of breaking SU(2) by the gravitational effects and of suppressing monopole production in the early universe.

A supersymmetric gut

We propose a grand unified supersymmetric theory based on SU(5) with spontaneously broken supersymmetry. The theory (really a class of theories) is completely realistic. In particular, supersymmetry partners of ordinary fermions and bosons are heavy. The model requires one fine-tuning in order to render the color triplet partners of the Higgs fields (which mediate proton decay) superheavy. This fine-tuning is stable against radiative corrections. At the tree level, the model contains two scales, the unification scale, of order 10 16 GeV, and the supersymmetry breaking scale, of order 10 10 GeV. The breaking of SU(2) × U(1) invariance arises as a radiative effect. The lightest of the new particles implied by supersymmetry are expected to have masses of order tens of GeV.

Broken SU(3) symmetry from quark interchange

The one-boson-exchange model is related to a bag-model quark-interchange mechanism for the hadronic interactions at low energy and momentum transfer. These mesonic interactions are a consequence of quark reflections in the color-confining hadronic surface region, where such events in neighboring hadrons are required to be paired for chiral invariance to hold in each perturbative hadronic interior.

Aspects of Grand Unified Models with Softly Broken Supersymmetry

The minimal SU(3)× SU(2)× U(1) gauge model with softly broken supersymmetry is studied in the framework of the standard grand unification. It is assumed that the supersymmetry is left intact at an energy scale μ≃ MX, the grand unification mass scale, except for Majorana masses of gauge fermions. The other soft breaking parameters at low energies are shown to be generated by renormalization effects. The gauge symmetry breaking SU(2)× U(1)→ U(1)em is also caused through radiative corrections. The super-GIM mechanism apparently works well to suppress flavor changing neutral interactions. The mass of the top quark is remarkably found to be constrained as 60 GeV ≾ mt ≾ 180 GeV. Futhermore various mass relations for unconventional particles are obtained as well as crude estimates for numerical masses of them. It is found that there is a plethola of new particles in a mass range from a few tens of GeV to a few hundred GeV.

Baryon magnetic moments in the broken-SU(6)-symmetry model

A simple factor representing the symmetry-breaking effects due to quark masses is introduced in the computation of the magnetic moments of baryons in the context of broken SU(6) symmetry.

Baryon Magnetic Moments in the Quark Model and Pion Cloud Contributions

Baryon magnetic moment is studied paying attention to the effects of pion cloud which is surrounding the 'bare' baryon whose magnetic moment is given by the quark model with broken SU(6) symmetry. The precisely measured nucleon magnetic moments are reproduced by the pion cloud contributions from the distance larger than 1.4 fm. The effects of pion cloud on the hyperon magnetic moments are also discussed. It is shown that the pion cloud contributions largely reduce the discrepancies between the quark model predictions and the recent accurate experimental data on the hyperon magnetic moments.

A possible SU(7) grand unified model with non-standard charged quarks, lepton and low-mass magnetic monopole

A possible SU(7) grand unified model with non-standard charged quarks, lepton and low-mass magnetic monopole is proposed. In this model, the quarks and leptons of the first and the second generations are the same as in the standard GUM, but the assignment of the fermions of the third and the fourth generations is quite different from the standard GUM. Although the charge of the top quark is 2 3 , the quark Q=− 1 3 , the τ lepton Q=−1, there are also two kinds of quarks with Q= 5 3 , − 4 3 and a lepton with Q=−2. The coupling of e− ν e, μ− ν μ and τ− μ τ is V − A. We break SU(7) down to SU(3) and U(1) em in three steps. We estimate the proton decay lifetime t p and the mass of the magnetic monopole M m . In the experimentally plausible ranges of the weak mixing angle sin 2 θ w( M w) and the strong-coupling constant α s( M w), 0.18⩽sin 2 θ w( M w) ⩽ 0.22, 0.15 ⩽ α s( M w) ⩽ 0.24, respectively, t p > 10 30 yr, which sensitively depends on the mass scale of the grand unified point, and M m ⋍ 10 6 GeV , which is almost independent of sin 2 θ w( M w) and α s( M w) and consistent with the big-bang theory of the universe.

PossibleSU(4)c×SU(3)f×U(1)model

An anomaly-free model of strong and electroweak interactions involving leptons and quarks in the SU(4)/sub c/ x SU(3)/sub f/ x U(1) gauge theory is constructed. After spontaneous symmetry breaking, it reduces to quantum chromodynamics for strong interactions and a broken SU(3) x U(1) model for electroweak interactions. As a limiting case it gives the same results as those of the Weinberg-Salam model in the low-energy region. The Weinberg angle is bounded by sin/sup 2/theta/sub W/<1/4 and becomes slightly less than 30/sup 0/ in the limiting case. Below the mass scale of SU(4)/sub c/ breaking there exists an inequality between the Weinberg angle and the strong coupling constant, which is consistent with experiments. A correction to the neutral current of the Weinberg-Salam model is suggested. A new conserved quantum number is introduced in this model and there exist several new fermions with masses lighter than 160 GeV. The Kobayashi-Maskawa expression of Cabibbo mixing for quarks may be obtained in the model, generalized to include several generations of fermions.

First and second order hadron mass formulas in internal SU(6)

We use broken SU(6) internal symmetry to derive the mass formulas amongst hadrons (1/2+, 3/2+, 0−, 1−) including second order mass contributions from symmetric 405 representation. Some hybrid mass relations are also obtained by relating second order parameters.