John R. Ellis

Supersymmetric Relics from the Big Bang

Abstract We consider the cosmological constraints on supersymmetric theories with a new, stable particle. Circumstantial evidence points to a neutral gauge/Higgs fermion as the best candidate for this particle, and we derive bounds on the parameters in the lagrangian which govern its mass and couplings. One favored possibility is that the lightest neutral supersymmetric particle is predominantly a photino ∼ γ with mass above 1 2 GeV, while another is that the lightest neutral supersymmetric particle is a Higgs fermion with mass above 5 GeV or less than O(100) eV. We also point out that a gravitino mass of 10 to 100 GeV implies that the temperature after completion of an inflationary phase cannot be above 1014 GeV, and probably not above 3 × 1012 GeV. This imposes constraints on mechanisms for generating the baryon number of the universe.

Weak Symmetry Breaking by Radiative Corrections in Broken Supergravity

Abstract Weak interaction gauge symmetry breaking can be generated by radiative corrections in a spontaneously broken supergravity theory, provided the top quark is heavy enough. In one class of such theories the weak Higgs vacuum expectation values are determined by dimensional transmutation a la Coleman-Weinberg, and may be considerably larger than the magnitudes of SUSY breaking mass parameters. In this scenario mt⩾65 GeV, the supersymmetric partners of known particles may have masses ⪡mW, the mass of the lighter neutral scalar Higgs boson is determined by radiative corrections, and there is some variant of a light pseudoscalar axion. In contrast to conventional Coleman-Weinberg models, the weak phase transition is second order and there is no likelihood of excess entropy production.

Search for supersymmetry in toponium decays

Although cosmology and unification suggest that the mass of the gluino is larger than about 14 GeV, in many theories of broken supersymmetry the photino γ, gluino g and one of the spin-zero partners t of the t quark can be lighter than mt− We calculate the decay rates for toponium →gg, γγ and tt and show that in many models they can be as large as, or larger than, the rate for toponium →e+e− decay. If it is kinematically accesible, the decay t→t + γ dominates the decays of toponium as well as those of naked top states.

Canonical Anomalies and Broken Scale Invariance

Abstract Canonical behavior of strong interactions at short distances causes an anomaly in the trace identity involving two electromagnetic currents and the energy-momentum tensor. The anomaly is connected with the high energy behavior of e + e − → γ → hadrons and the ϵ(700)γγ coupling constant.

Strong and weak CP violation

Abstract We study the renormalization of the QCD vacuum parameter θ which arises from CP violation in the weak interactions. In the Kobayashi-Maskawa extension of the Weinberg-Salam model to include six quarks, the first renormalization of θ occurs in O( α 2 ) and is apparently O(10 −16 ). If we assume that θ = 0 at some unknown “relaxation” scale μ 0 , this renormalization makes a contribution to the neutron electric dipole moment which is probably O(10 −31 to 10 −32 )cm and smaller that the purely perturbative contribution. Infinite renormalization of θ may first occur in O( α 7 ), and we isolate a topological class of diagrams of this order which do indeed require infinite renormalization of θ. For any reasonable choice of the relaxation scale μ 0 , the residual finiteθ renormalization is much smaller than the first finite O( α 2 ) contribution. We finish with some remarks about θ renormalization in other weak interaction models of CP violation.

Observable gravitationally induced baryon decay

We find that in supersymmetric theories gravitodynamic effects scaled by the inverse of the Planck mass can induce baryon decay at an observable rate. In a minimal supersymmetric (susy) grand unified theory (GUT) the dominant gravitationally induced baryon decay mode is B → ν + K, with a likely admixture of p → (e+ or μ+) + K. As a by-product, we present an improved estimate of Higgs-mediated baryon decay branching ratios in minimal susy GUTs. We consider the possibility that a loss of quantum coherence may be observable in gravitationally induced baryon decay, but argue that this would be difficult to reconcile with successful experimental tests of quantum mechanics.

Search for supersymmetry at the pp collider

Abstract Many models of broken supersymmetry predict the existence of supersymmetry fermions χ±,0 with masses less than the W± and Z0. Often there are two light neutral fermions χ0, even in models with large gaugino masses. The W± have large branching ratios for decays into χ±+χ0, with the χ± subsequently decaying into χ0 plus hadrons or leptons. We propose looking at the CERN p p collider for W± production and decay into supersymmetric fermions, a likely signature being “zen” events with one broadened hadronic jet system recoiling against invisible missing transverse energy.

Search for Neutral Gauge Fermions in

Many broken supersymmetric theories contain two light neutral fermions χ, χ′ which are mixtures of supersymmetric partners of the gauge and Higgs bosons. The heavier of these (χ′) can be produced in e+e− annihilation by e+e− → χχ′ or χ′χ′ with cross sections that may be comparable to that for e+e− → νμνμ : σ = (0.1 to 10) pb at √s = 30 GeV. The χ′ likes to decay into an e+e− or μ+μ− pair and a χ, which is likely for cosmological reasons to be almost a pure photino γ Associated production e+e− → χχ′ can lead to a one-sided “zen” event structure with visible decay products in one hemisphere only, while e+e− → χ′χ′ can give 4-lepton final states with missing energy.

e^+ e^-

Abstract We discuss the analysis of possible 3-jet events in e + e − annihilation and elsewhere. If one selects events with low thrust, the particles recoiling away from the thrust axis should appear as a pair of back-to-back jets in their centre-of-mass system. The angular distributions of such jets are very different in the case of vector gluon bremsstrahlung from what they would be for scalar gluons, or for the 3-gluon decay of a heavy quarkonium resonence. We outline a similar analysis of 3-jet events in photoproduction.

Annihilation

Abstract We study the interplay of supersymmetry and certain non-compact invariance groups in extended supergravity theories (ESGTs). We use the N = 4 ESGT to demonstrate that these symmetries do not commute and exhibit the infinite-dimensional superinvariance algebra generated by them in the global limit. Using this result, we look for unitary representations of the full algebra. We discuss the implications of our results in the context of attempts to derive a relativistic effective gauge theory of elementary particles interpreted as bound states of the N = 8 ESGT.