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.     

正负电子湮灭过程的核子激发态N*产生(英文)

目前,正负电子湮灭过程的核子激发态N*产生的实验数据主要来自于粲偶素能区。粲偶素衰变到核子激发态过程类似于其类时电磁形状因子测量过程,正反粲夸克短程湮灭提供了近乎于点源的胶子强子化过程。与γN,eN,πN反应互补,这一新的N*产生源具有同位旋和低自旋筛选的优势。综述了正负电子湮灭过程的核子激发态N*产生的实验情况和相关的唯象进展,同时讨论未来发展的一些新方向,如正负电子湮灭过程的核子激发态N*产物的一些新来源等。Up to now, the N* production from e+e- annihilations has been studied only around charmonium region. Charmonium decays to N*s are analogous to (time-like) EM form factors in that the charm quark annihilation provides a nearly pointlike (ggg) current. Complementary to other sources, such as πN, eN and γN reactions, this new source for N* spectroscopy has a few advantages, such as an isospin filter and a low spin filter. The experimental results on N* from e+e- annihilations and their phenomenological implications are reviewed. Possible new sources on N* production from e+e- annihilations are discussed.     

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.     

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.     

An optimal scheme for top quark mass measurement near the tt threshold at future e+e- colliders

A top quark mass measurement scheme near the tt production threshold in future e⁺e^- colliders, e.g.the Circular Electron Positron Collider (CEPC), is simulated. A χ² fitting method is adopted to determine the number of energy points to be taken and their locations. Our results show that the optimal energy point is located near the largest slope of the cross section v. beam energy plot, and the most efficient scheme is to concentrate all luminosity on this single energy point in the case of one-parameter top mass fitting. This suggests that the so-called data-driven method could be the best choice for future real experimental measurements. Conveniently, the top mass statistical uncertainty can also be calculated directly by the error matrix even without any sampling and fitting. The agreement of the above two optimization methods has been checked. Our conclusion is that by taking 50 fb^-1 total effective integrated luminosity data, the statistical uncertainty of the top potential subtracted mass can be suppressed to about 7 MeV and the total uncertainty is about 30 MeV. This precision will help to identify the stability of the electroweak vacuum at the Planck scale.     

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.     

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.     

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 $\text{v}\text{W}{}_2$.     

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      

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.     

SUSY effects in Higgs production at high energy e+e- colliders

Considering the constraints from collider experiments and dark matter detection, we investigate the SUSY effects in the Higgs production channels e⁺e^-→Zh at an e⁺e^- collider with a center-of-mass energy above 240 GeV and γγ→h→bb at a photon collider with a center-of-mass energy above 125 GeV. In the parameter space allowed by current experiments, we find that the SUSY corrections to e⁺e^-→Zh can reach a few percent and the production rate of γγ→h→bb can be enhanced by a factor of 1.2 over the SM prediction. We also calculate the exotic Higgs production e⁺e^-→Zh₁ in the next-to-minimal supersymmetric model (NMSSM) (h is the SM-like Higgs, h₁ is the CP-even Higgs bosons which can be much lighter than h). We find that at a 250 GeV e⁺e^- collider the production rates of e⁺e^-→Zh₁ can reach 60 fb.     

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°.