On duality in e+e- annihilation

With the help of a relativistic generalization of a formula for the leptonic width of quarkonium in the quasiclassical approximation it is shown that the sum of a sufficiently large number of total cross sections for the production of the quarkonium state (Q$\text{Q}$)_n in e⁺e^- annihilation is equal to the total cross section for production of a quasi-free quark- antiquark pair Q$\text{Q}$.     

Scalar electron production in e+e- annihilation at high energies

The cross section for single and pair productions of scalar electrons in e⁺e^- annihilation are calculated in the energy range of TRISTAN, SLC and LEP with specific emphasis on the contribution from the Z⁰ boson and the zino.     

Implications of e+e- → μ+μ-, e+e- at PETRA/PEP energies on electroweak theories

The implication of measurements of μ pair production and Bhabha scattering at PETRA/PEP energies on electroweak theories are analysed in terms of single gauge boson as well as multi weak boson theories.     

Flavour separation by means of transverse beam polarization in high-energy e+e- annihilation

Transverse beam polarization is in e⁺e^- annihilation at high energies shown to lead to a strong azimuthal variation in the flavour composition of the produced quark-antiquark pairs. We describe, in the SU(2) × U(1) model, a way in which this could be used to obtain flavour-specific information on the quark fragmentation functions. In inclusive charged particle rates the effect might be much reduced, but still observable.     

Distinctive signatures for new particles in e+ e− annihilation and z-decay

New particles and new interactions reveal themselves most clearly where standard model contributions are negligibly small. A prominent example with this advantage is the one-lepton inclusive longitudinal structure function (W_L) in e⁺ e^? annihilation and Z-decay. We discuss general features of this approach and present structure functions for two types of new particles (heavy charged fermion, e.g. new sequential lepton or top quark; and supersymmetric scalar lepton, i.e. slepton), along with the (small) standard model “background”. The x-dependence of W_L provides a distinct signature of the identity of the new particle. Extensions of this approach are discussed.     

Two-particle correlations in e+e− annihilation

We present measurements of two-particle angular correlations in hadron jets produced in e⁺e^? annihilation between 7.7 and 31.6 GeV c.m. energy. The data are compared to predictions of high order perturbative QCD calculations.     

Measurement of the W boson mass and width in e+e- collisions at LEP

The mass of the W boson is determined from the direct reconstruction of W decays in WW→qq̄qq̄ and WW→ℓνqq̄ events in e⁺e^- collisions at LEP. The data sample corresponds to an integrated luminosity of 683 pb^-1 collected with the ALEPH detector at centre-of-mass energies up to 209 GeV. To minimise any effect from colour reconnection a new procedure is adopted in which low energy particles are not considered in the mass determination from the qq̄qq̄ channel. The combined result from all channels is where FSI represents the possible effects of final state interactions in the qq̄qq̄ channel and LEP indicates the uncertainty in the beam energy. From two-parameter fits to the W mass and width, the W width is found to be      

Scale breaking in inclusive charged particle production by e+e− annihilation

The scale cross section $\text{s}\text{d}\text{σ}\text{d}\text{x}{}_{\mathrm{<mtext>p</mtext>}}$ for inclusive charged-particle production in e⁺e^? annihilation has been studied for c.m. energies W between 12.0 and 36.7 GeV. Scale breaking is observed. For x_p>0.2 the cross section decreases by ≈20% when W increases from 14 to 35 GeV. The production angular distribution was used to separate the longitudinal and transverse cross-section contributions and to determine the ratio of the structure functions $\text{m}\text{W}{}_1$ and $\text{v}\text{W}{}_2$.     

Photino-photino-photon production in e+e− annihilation

The cross section for production of single photons in the process $\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→ γ}\text{γ}\text{γ}$ is calculated including selectron propagator and photino mass effects and is found to be significantly smaller than the local limit for selectron masses ? 35 GeV/c². Numerical results for the cross section are obtained as a function of selectron masses for photino masses $\text{m}{}_{\mathrm{<mtext>\gamma </mtext>}}\text{? 10}\text{GeV}\text{/c}{}^2$ and electron beam energies E = 14.5, 25, and 35 GeV appropriate to PEP, PETRA, and TRISTAN, respectively.     

Multiplicities in electroproduction and e+e− annihilation

It is shown how more sophisticated versions of the parton model can replace the naive expectation of final state hadrons being produced in ep or e⁺e^? collisions in two jets of finite multiplicity, well-separated in rapidity, with a picture that permits the rapidity gap to be filled in and allows the multiplicity to rise with energy, even up to the limit imposed by energy conservation. Large multiplicity is shown to imply a rather slow approach to scaling and a significant tail in the transverse momentum distribution.     

Cosmic gamma-rays associated with annihilation of relativistic e+ −e− pairs

Results of electron-positron annihilation spectrum investigations are reported. The radiation spectra of an e⁺ ?e^? relativistic maxwellian plasma are presented. We consider the particular case of positron annihilation on electrons at rest. It is shown that for positrons with a suprathermal power law distribution the radiation due to annihilation exceeds bremsstrahlung up to at least ω ≈ 100 mc².     

Scaling in e+e− annihilation into hadrons

The possibility is discussed that the violation of scaling observed in e⁺e^? annihilation is due to the opening of the baryon pair channels. One particle distributions are assumed to scale apart from final state interactions. The threshold effects are computed.     

Experimental results on a search for narrow resonances in e+e- annihilation into hadrons in the mass region 2520–2990 MeV

A search for possible new resonances produced in e⁺e^- annihilation at Adone has been performed in the mass region 2520–2990 MeV. No evidence has been found for new resonances. We obtain an upper limit on the energy integrated resonant cross section of about 6% of the J/ψ (3100) corresponding value.     

A QCD model for e+e− annihilation

A QCD model for e⁺e^? annihilation is presented, and its consequences are compared with experimental data. The model involves production of a shower of partons described by a simple approximation to QCD perturbation theory, and decay of colour singlet clusters of produced partons into hadrons through a simple phase space process. The model reproduces most known theoretical features of QCD, and, with certain choices of parameters, appears to correspond well with experimental results.     

A possible scheme to obtain e-e- and e+e- collisions at energies of hundreds of GeV

As a contribution to the discussion on very long term developments in the field of high energy physics, it is pointed out that it is possible to devise e^-e^- and e⁺e^- colliding beam machines which are not affected by the large synchrotron losses typical of conventional storage rings. The scheme proposed here makes use of two collinear superconducting linacs which at the same time accelerate and recover the energy fed to the electron and positron beams.     

W° effects in inclusive e+e− annihilation

A general parton model is used to formulate W° effects in inclusive e⁺e^? annihilation. These effects are of the order 1% in the case of inclusive pion production at CM energies of 10 GeV with the Weinberg W°.     

Energy-energy correlations in e+e− annihilation into hadrons

Measurements of energy-energy correlations in hadronic final states produced in e⁺e^? annihilation at c.m. energies between 7.7 and 31.6 GeV are presented. The data are compared to perturbative QCD predictions. Good qualitative agreement above 20 GeV c.m. energy is found. The importance of non-perturbative effects is discussed, as well as the detailed behaviour of the correlation near 180°.     

The on-shell QCD quark form factor and its determination from two-particle correlations in e+e− annihilation

Opposite side correlations in hadron jets produced in e⁺e^? annihilation provide a possibility to measure directly the on-shell QCD quark form factor. Comparing recent PLUTO data with the leading log prediction yields 0.54 ± 0.1 GeV for the QCD parameter Λ.     

Isospin bounds and bose condensation in e+e− annihilation

We derive isospin bounds for two particle correlations in e⁺e^? → γ → Nπ, discuss the physical significance of saturation of the upper bound and present various multiplicity distributions for this case.     

A new unitarity bound on e+e− annihilation

Unitarity relates σ_h the electron-positron annihilation cross-section into hadrons and σ_μ the cross-section into muon pairs. This relation provides much more restrictive bounds on σ_h than the simple unitarity bound, for the case in which the hadronic channels dominate the total annihilation cross-section.