Electron Pair Production Research Articles

On the calculation of e +e − pair production at low kT in high-energy hadronic collisions

We discuss the calculation of electron pair production due to internal conversion of photons produced by the bremsstrahlung of charged hadrons created in high-energy collisions and the interference of this contribution with photons produced directly. We point out that the leading bremsstrahlung contribution at large angles is controlled by the level of charge fluctuation, which is itself related to a sum rule involving the charge correlation functions. The next two leading terms can also be estimated and the level of e +e − pairs can be predicted with some confidence. The expected single-electron signal at small transverse momentum, after allowing for experimental acceptance cuts, is not quite enough to completely explain the large yield suggested by recent high-energy experiments; however it is sufficient to be considered a dominant source. Like π 0 Dalitz pairs, this signal increases as p T → 0. We also indicate differences in the mass spectrum.

Study of photons produced simultaneously with the J/ψ particles at the CERN intersecting storage rings

As a part of the study of the inclusive production of electron pairs in pp collisions at the CERN Intersecting Storage Rings (ISR), a search has been performed for additional photons accompanying J/ψ particles. The results suggest that (43±21)% of the J/ψ's are produced via the photonic decay of one of the χ(3.5) states.

The cross section for the production of massive electron pairs and the ϒ(9.5 GeV) in proton-proton collisions at the CERN ISR

Measurements of the cross section for the production of electron pairs with invariant masses between 4 and 8.7 GeV are presented as a function of the centre-of-mass energy ( s = 28 to s = 62 GeV ) of the colliding proton beams. A significant excess of events is observed in the region 8.7 to 10.3 GeV; these are ascribed to the ϒ(9.5 GeV) resonances and estimates of the production cross sections are given.

The Coulomb correction to electron pair production by intermediate-energy photons

The Coulomb correction to the total cross section for intermediate-energy pair production is evaluated in terms of a high-energy-expansion formula, with the Davies-Bethe-Maximon correction as the leading term, followed by terms proportional to k −1ln 2 k, k −1ln k, k −1 etc., the coefficients of which are determined by fitting to the Øverb∅-Mork-Olsen exact low-energy results. The formula is estimated to be accurate within a few tenths of a per cent for photon energies between 3.5 m e c 2 and infinity.

Electron pair production by 830 MeV/c π+ compared with other recent datacompared with other recent data

Electron pair production by 830 MeV/c π+ compared with other recent datacompared with other recent data

Electron production by 4.0 GeV/ cπ+p interactions

We have investigated electron production in 4.0 GeV/ c π +pinteractions. Limits to direct electron pair production are measured and an example of ϱ 0 or ω 0 decay to e +e − is observed. The ratio of the number of singly produced electrons to the total number of charged pions is less than 6 × 10 -5 (at the 95% confidence level).

Analytic continuation of electron pair production to the tip of the positron spectrum in point-coulomb calculation

Analytic continuation of electron pair production to the tip of the positron spectrum in point-coulomb calculation

Numerical results of angular cross sections of electron pair production in a point-Coulomb potential

Numerical results of angular electron pair-production cross sections are given for the $\ensuremath{\gamma}$-ray sources $^{60}\mathrm{Co}$ and $^{208}\mathrm{Tl}$. Cross sections are obtained analytically for a point-Coulomb potential, using an exact partial-wave formulation. Angular distributions are essentially unaffected in shape by the screening effects, as shown by Tseng and Pratt's calculations, so our curves can be useful to experimentalists. Moreover, they are computed at the tip region of the spectrum where screening effects are almost negligible.

Electromagnetic Interactions of High Energy Cosmic Ray Muons

AbstractThis paper investigates the electromagnetic interactions of muons. The various processes such as knock‐on electron‐, bremsstrahlung‐, direct electron pair production, and nuclear interactions are described in detail. The energy range concerned extends from 109 eV up to 1015 eV for primary muons and from 108 eV up to 1014 eV for energy transfers to the secondaries.On the one hand the measurement of muon interactions represents a test of quantum electrodynamics. On the other hand the high energies available in cosmic rays would possibly lead to the measurement of new processes or the detection of new particles. One hopes to find in the high energy domain the answer to the question why the muon exists at all and if there are properties (apart from differences in mass, lifetime, and lepton number) which distinguish it from a mere heavy electron.The different experimental techniques are described and the various experimental results on muon interactions are presented and compared with relevant QED‐theories.Observed deviations between theory and experiment and anomalies in muon interactions are critically investigated and discussed in the light of experimental difficulties and interpretation problems. In general, agreement between theory and experiment is found, i.e. QED‐theories describe the results adequately. However, some experiments claim to have detected anomalies in muon physics in the cosmic ray beam. But the hypotheses on new processes and new particles in the high energy range do not withstand a critical analysis. It is concluded that the observed deviations can be understood in the framework of conventional theories.

On the use of coherent electron-pair photoproduction and bremsstrahlung obtained from a 400 GeV proton-synchrotron

It is shown that the coherent electron-pair production by very-high-energy photons in a crystal converter could be used in order to obtain a cleaner electron beam from the CERN SPS or Batavia 400 GeV proton synchrotron. Coherent electron-pair cross section in a tungsten crystal has been integrated over the photon energy spectrum which fits the inclusive reaction ISR data. Performances of several crystals have been evaluated before selecting the tungsten one.

Hard-photon distribution in radiative electron pair production

Hard-photon distribution in radiative electron pair production

The cosmic radiation and its significance

the beginning was the bang, and the bang created the world. As far as is permitted by the austerity of our discipline, this statement has become the credo of most scientists of our generation. It is accepted, one is tempted to say, as a great truth revealed by our Lord Nature. Yet our master Science has taught us to be sceptical even of apparent revelations. Proof, not belief, must support what we infer from them. And with respect to that primeval act of creation this ruling poses a particularly difficult task for us to solve. How are we to recount from the present to a distant past the history of our world when no traces of the big bang can be left but whispers, the results of the enormous dilution by expansion and of interactions continuing for an aeon? Evidently our chance lies in finding characteristic whispers, and fortunately we seem to have found just these in the universal black-body radiation. It is beyond the scope of this contribution to discuss the reasons which allow us to take this position, or even to argue about the certainty of identification of the radiation. Suffice it to say that the experimental data are compatible with a black-body spectrum, but that its universal character, its extension beyond galactic space, needs further confirmation. This is why observations on cosmic radiation can provide crucial tests. It may well be that the bulk of the cosmic-ray particles detected by our apparatus has never seen metagalactic space but originates and remains trapped in our Galaxy; the arguments of the case will be presented in the following sections. But the huge output in synchrotron radiation from the strong radio sources is irrefutable proof that also in many distant source regions charged particles are accelerated to cosmic-ray energies. Certainly some of them will leak out into intergalactic space, building up an extragalactic component of cosmic radiation. One may debate its relative significance compared with the home-made galactic component, but one cannot deny its existence. Undoubtedly, therefore, interactions will take place between a universal black-body radiation--if it exists--and the more or less intense metagalactic cosmic radiation. What kind of interactions do we expect? Since we know that the cosmic radiation contains both nuclear particles--protons and heavier nuclei--and electrons, there will be photonuclear reactions and Compton processes. Among the first we shall find collisions of the black-body photons with energetic heavy nuclei, leading to a disruption of the nuclei and to electron-pair production. In addition, cosmic-ray protons colliding with black-body photons will again produce electron pairs, and at sufficiently high energies also pions in (7,p) interactions. For cosmic-ray electrons the inverse Compton effect, the transfer of a large fraction of the electron energy to a black-body photon, is the dominant process. These introductory remarks outline the course we must take in our search for evidence of the big bang. We shall have to derive quantitative estimates of the various effects mentioned above, the interplay between a universal black-body radiation and a metagalactic cosmic radiation of still undetermined intensity. We shall have to deduce this intensity under the assumptions of the various rival theories of cosmic-ray origin, and to evaluate the resulting black-body-radiation effects. Comparison with the experimental data on the primary cosmic radiation will then tell us what message the whispers still

Direct Electron Pair Production by High-Energy Muons

Direct Electron Pair Production by High-Energy Muons

I. EXPÉRIENCES PASSÉES ET FUTURES / I. PAST AND FUTURE EXPERIMENTSRESEARCHES IN FRASCATI ON THE REACTIONS e+e–→ e+e–+ X. THE RESULTS OF THE "γγ GROUP"

A general survey is given of the possibilities for performing photon-photon collisions with the Frascati storage ring ADONE, and the corresponding set-ups used. The experiments already performed by the γγ group are considered in particular. At beam energy 1 400-1 500MeV, 46 events of the type e– e+ → e– e+ e– e+ and a few events of the type e– e+ → e– e+ µ– µ+ were analyzed. More than half of the electron-pair production events (with tagging of only one forward-scattered primary electron) did not belong to the photon-photon collision mechanism (two quasi real photons), but to the mechanism suggested by Cabibbo and G. Parisi (one quasi real and one highly virtual photon).

Bootstrapped electron pair production in extra-galactic sources

Possible observational peculiarities due to the occurrence of electron pair production in extra-galactic sources are studied; the case of steep spectra is outlined; a possible enhancement of the pair production reaction due to its very occurrence is also proven for a set of models built on the basis of the data observed for 3C 273 and NG-C 1275.

Measurements of Electron-Pair-Production Cross Sections

A number of cross sections associated with electron pair production have been measured in the photon energy range 10-300 MeV in Ilford G-5 emulsion (Z/sub eff/ approx equal 21). Measurements include the distribution of the recoil momentum and scattering angle of the target nucleus, the divergence angle between the pair members, the energy partition, the effect of photon polarization, and the absolute pair production cross section. Agreements and disagreements with the theory and previous measurements are discussed. (auth)

Estimates for the efficient production of antihydrogen by lasers of very high intensities

Starting from the non-linear relativistic equations of motion for charged particles in the very high intensity fields of laser radiation, the maximum kinetic energy ɛkin of the resulting oscillation is derived exactly. In non-relativistic conditions ɛkin agrees with the well-known valuee2Ev2/(2m0ω2|n|), showing a dependence on the rest massm0 of the particle. In the relativistic case, the mass dependence vanishes. The multipole radiation is calculated on the basis of Sommerfeld's formula for relativistic conditions. It is shown that this radiation is not important for oscillation energies up to\( \in _{kin^{mr} } \)=70m0c2 for electrons in neodymium glass laser radiation and up to higher values for CO2 lasers and for protons. With the limitationm0c2 < ekin <\( \in _{kin^{mr} } \), the formula for ɛkin is used to calculate the pair production (a) for singly oscillating particles in vacuum without collisions and (b) for plasmas with collisions. Taking into account the local increase of the effective electric laser field near the cut-off density due to the decrease of ¦n¦ (n is the complex refractive index), there is the possibility of efficient proton pair production at intensities of 1019 W cm−2 for neodymium glass lasers and of 1017 W cm−2 for CO2 lasers, besides electron pair production.

Radiative Corrections top+p→l++l−+``Anything''and Application to Muon-Electron Symmetry

Radiative corrections, to order $\ensuremath{\alpha}$, are carried out to the lepton lines in the process $p+p\ensuremath{\rightarrow}{l}^{+}+{l}^{\ensuremath{-}}+``\mathrm{anything}''$. Expressions are derived which relate the radiative corrections, due to the emission of soft photons, and of hard photons from the lepton lines, to the observed cross section for production of electron or muon pairs. These expressions are used to predict the difference, based purely on electromagnetic interactions, between the cross sections for production of electron and muon pairs. As a specific example, computations are done using the BNL data for production of lepton pairs in hadron-hadron collisions.

Direct Production of Electron Pairs by Energetic Protons

In a study of nuclear collisions produced by 200-GeV protons in emulsion, we have found eight events attributable to the direct production of electron pairs by protons. A crude measure of the cross section, 6.7 \ifmmode\pm\else\textpm\fi{} 2.4 mb, is obtained. This result is viewed in relation to foregoing work on direct pair production by energetic leptons.

Direct pair production by positive and negative electrons in a hydrogen bubble chamber

The production of electron pairs by negative and positive electrons in the energy region 0.65 – 5.8 GeV has been investigated in the DESY 81-cm hydrogen bubble chamber. The effective cross section σ = 0.62 ± 0.04 mb averaged over the energy spectrum of incident electrons is found to be in good agreement with the predictions of quantum electrodynamics. The energy distribution of created pairs as well as the dependence of the total cross section on energy are best represented by the expression of Murota, Ueda and Tanaka with the constant c = 0.66 ± 0.17 0.24 and by Bhabhá's formula with the constants c 1 = 1 and c 2 = 2.8 ± 0.7 0.9. The contribution of the interference term between space-like and time-like Feynman diagrams to the cross section is estimated to be less than about 10% and to fall off with an increase of the incident energy.