Colliding Beam Experiments Research Articles

Masses of baryons and mesons

Although there arc several theories of heavy-mass generation, one of the central problems of elementary-particle physics is the calculation of the particle masses. The mechanisms of the gauge theories (1) and others (2) do not yield the mass spectra for baryons and mesons. On the other hand the e+e colliding-beam experiments suggest generation of hadrons by a mechanism based on photon collisions, which implies a simpler Lagrangian We consider the Lagrangian for a spinor and vector field

Radiative effects for resonances with applications to colliding beam processes

New expressions are presented for radiative corrections to colliding beam experiments in presence of narrow resonances, including interference effects. These are applied to ψ (3.1) and ψ (3.7) to obtain the values ( Γ e Γ h/ Γ)=(4.0±0.2) keV for ψ (3.1) and (2.8 ± 0.3) keV for ψ (3.7).

On the electron-muon mass ratio

The quantum electrodynamics (QED) of electrons is considered as a theory with a passive dilatation invariance which is perturbed by the electromagnetic coupling to hadrons and muons. A stability criterium is introduced and evaluated in lowest order of the perturbation. The resulting expression for the electron-muon mass ratio in terms of the vacuum polarization can be tested in e + − e − colliding beam experiments.

State of the Art of Drift Chambers

The basic properties of drift chambers such as space resolution are discussed. The performance of various types of drift chambers is reported, e.g. chambers with high space and time resolution (Δ x = 0.25 mm fwhm, Δ t = 6.3 ns fwhm), very large area chambers (ca. 16 m2) for a neutrino experiment, cylindrical chambers for colliding beam experiments.

Confirmation of the new 3700 MeV narrow resonance in e +e −-collisions

The two new, very narrow resonant states discovered at Brookhaven and SLAC were confirmed at the storage ring DORIS of DESY in e +e −-colliding beam experiments.

Multiplicity measurements ine+e−colliding-beam experiments

We discuss the sensitivity of the multiplicity measurements in ${e}^{+}{e}^{\ensuremath{-}}$ colliding-beam experiments to small background effects, such as radiative corrections and two-photon processes.

Report on DORIS

The double storage ring DORIS has been in operation since the beginning of 1974. Colliding beam experiments started in November of 1974. Luminosities of 1030cm-2s-1 at 2 GeV are routinely reached during experimental runs. Beam life times are 8 to 11 hours. At the present time luminosity is limited by phase instabilities.

The two-photon process for particle production in colliding beam experiments

Cross sections for particle production by the two-photon process for the reactions ee→ee X with X= π 0 or η and X= π + π − or π + π − are calculated exactly by numerical techniques and are compared with predictions of the double equivalent photon approximation (DEPA). Implications of these results as to the validity of the DEPA are discussed and an attempt is made to summarize and clarify some of the earlier criticisms of this approximation.

Experimental consequences of quark structure

Some experimental consequences of endowing quarks with both a finite size (form factor) and an anomalous magnetic moment are investigated within the context of the naive quark-parton model. Our discussion is limited to experiments which will be completed in the near future such as deep-inelastic electroproduction at large angles and high energies, electron-positron colliding beam experiments, high-energy neutrino and antineutrino scattering, and the production of $\ensuremath{\mu}$ pairs. The following are some definite predictions of the model which can be tested: (a) The ratio of longitudinal to transverse cross sections must begin to rise beyond $\ensuremath{-}{q}^{2}\ensuremath{\sim}10$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$, reflecting a considerable scaling violation in the conventional ${W}_{1}$ structure function; (b) the normalized single-particle distribution functions $(\frac{1}{\ensuremath{\sigma}})(\frac{d\ensuremath{\sigma}}{dz})$ ($z$ being the fractional energy carried off by the detected particle) should scale in both $ep$ and ${e}^{+}{e}^{\ensuremath{-}}$ processes; (c) the approach to scaling in these distributions should be much slower for smaller values of $z$; (d) in ${e}^{+}{e}^{\ensuremath{-}}$, the single-particle distribution function $s(\frac{d\ensuremath{\sigma}}{dz})$ should violate scaling, especially for smaller values of $z$; (e) there should be only small deviations, if any, from scaling in antineutrino scattering whereas deviations in neutrino scattering should be considerable. Finally, similar experimental consequences of the presence of a second-class current in the weak interactions are explored.

Final-state interactions in radiative production of pions in colliding-beam experiments

The contribution of final state interactions of the pions in the process e + e −→ ππγ are calculated. It is noted that this may be used A) to obtain the zero isospin ππ s-wave in the ϵ-region, or B) if knowledge of this wave is assumed, to obtain a good estimate of the background for e + e − → ππ

Possible evidence for quark substructure from electron-positron colliding-beam experiments

By endowing quarks with a size and a small anomalous magnetic moment, it is shown that the rise in the ratio $\frac{\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{all}\mathrm{hadrons})}{\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})}$ with center-of-mass energy can be simply explained while leaving the observed scaling phenomenon in deep-inelastic electron scattering intact. Speculations and tests of the model are discussed.

Spin motion in e +e − storage rings

General properties of the spin motion in e +e − storage rings are studied in order to determine the conditions where radiative beam polarization is likely to occur. A general first-order theory of depolarization is developed and applied to specific examples of non-resonant depolarization in storage rings. It is found that under many practical conditions radiative beam polarization should occur and therefore the beam polarization will be a significant parameter in high-energy e +e − colliding beam experiments.

Electron-Positron Annihilation into Hadrons and Landau's Hydrodynamic Model

The multiplicity and inclusive single-particle distribution for ${e}^{+}+{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\pi}+X$ are calculated for Landau's hydrodynamic model. At 3 and 5 GeV the collective motion is less important than the thermal motion. The average pion energy obtained in the Stanford linear-accelerator colliding-beam experiment is consistent with either an ultrarelativistic equation of state or one based on the observed hadron spectrum.

The possible role of two-photon processes in high-energy colliding-beam experiments

A critical analysis is presented of the theoretical expectations for the process $gamma$$gamma$$Yields$ hadrons and its implications for high energy e$sup +$e$sup -$ annihilation into hadron. (FR)

Hadron vacuum polarization effect for muon pair production in positron-electron collision

I t is expected to have various information on the structure of hadrons from the electron-positron colliding-beam experiment (1.2). The purpose of this paper is to understand the effect of vacuum polarization of hadrons for the muon pair production up to, say, 2000 MeV total energy by taking into account the well-established vector mesons p, co, 0 and p'(1600) (s). In addition ?,o a general investigation of the effect for the lowest-order QED mechanism we are especially concerned with the vacuum polarization due to co-meson so as to determine the associated parameters including p-o~ interference effect. Experimentally, the vacuum polarization effect due to 0-meson has already been studied and the parameters associated with this effect have been established at a certain degree (4), so that the problem under consideration will be studied in a comparative manner with that phenomenon. In what follows a careful study at and around the energy corresponding to the co mass will clarify the problem under consideration. The e+e---> ~+~tcross-section, which takes into account the modification of the photon propagator due to vector mesons, is obtained by a Breit-Wigner formula for a(e+e-~Y)

Hadron production by electron-positron colliding beams

Various considerations and conjectures are made on the surprisingly large total cross section for hadron production which has recently been observed in the ${e}^{+}\ensuremath{-}{e}^{\ensuremath{-}}$ colliding-beam experiment at the Cambridge Electron Accelerator. First, they focus on the relative magnitude of cross sections for one-photon annihilation and for the two-photon process. Second, the asymptotic limit $R$ of the ratio $\frac{\ensuremath{\sigma}({e}^{+}+{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons})}{\ensuremath{\sigma}({e}^{+}+{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}+{\ensuremath{\mu}}^{\ensuremath{-}})}$ is predicted to be $R\ensuremath{\cong}12{\ensuremath{\pi}}^{2}({{f}_{p}}^{\ensuremath{-}2}+{{f}_{\ensuremath{\omega}}}^{\ensuremath{-}2}+{{f}_{\ensuremath{\varphi}}}^{\ensuremath{-}2})=5.5\ifmmode\pm\else\textpm\fi{}0.7$ from the PCDC (partially conserved dilation current) anomaly and vector-meson dominance, and estimated to be less than 15 for $\ensuremath{\Gamma}(\ensuremath{\epsilon}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}})=400$ MeV from the first evidence found at Frascati for hadron production by the two-photon process. A comment is also made on the present and future ${e}^{+}\ensuremath{-}{e}^{\ensuremath{-}}$ colliding-beam experiments at SLAC and DESY.

Large angle pair production in colliding beam experiments

Large angle pair production in colliding beam experiments

A suggestion for investigating electron-muon and electron-pion scattering with electron-positron colliding beams

We show that it is possible, in principle, to study the scattering between an almost real muon or pion and an electron in an e– e+ colliding beam experiment where one large-angle electron and one large-angle muon or pion would be measured in the final state. In the muon case, the counting rate should be high enough to allow this experiment to be performed with electron-positron storage rings of the next generation.

The two-photon process for particle production in colliding beam experiments

The two-photon process for particle production in colliding beam experiments

Wire spark chambers with magnetostrictive readout

Abstract We describe here the design criteria, construction details and developmental tests of magnetostrictive spark chambers, particularly those used in the colliding beam experiments at the Cambridge Electron Accelerator. We also present results of tests on efficiency, resolution and shower detection of positrons and photons.