"Equivalent photon approximation. Range of validity, accuracy, etc."

HAL Id: jpa-00215533

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Submitted on 1 Jan 1974

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”Equivalent photon approximation. Range of validity, accuracy, etc.”

V. Budnev, I. Ginzburg, G. Meledin, V. Serbo

To cite this version:

V. Budnev, I. Ginzburg, G. Meledin, V. Serbo. ”Equivalent photon approximation. Range of validity, accuracy, etc.”. Journal de Physique Colloques, 1974, 35 (C2), pp.C2-121-C2-122.

�10.1051/jphyscol:1974223�. �jpa-00215533�

CONTRIBUTIONS

Large angle pair production in colliding beam experiments

via one photon. The case of polarized particles is also discussed.

Abstract.

Large angle muon and pion pair

electroproduction cross section for the collisions of On the photon spectrum emitted high energy electrons and positrons has been calcu- at large angles in high-energy e f e - collisions lated. The production of the intermediate resonance V. S. FADIN

O f and 2' states has been considered in case of

pion production. Nuclear Physics Institute, Novosibirsk (USSR)

(*)

Nuclear Physics Institute, Novosibirsk (USSR). V. A. KHOZE

Nuclear Physics Institute, Leningrad (USSR)

Abstract.

The authors study in particular the Quasi-real photon approximation for describing reaction e+ e-

e+ e- e+ e- ,,, occurring via two-

electroproduction processes photon exchange.

Abstract.

A general approach is formulated for describing two-photon electroproduction processes (e* e -

e* e- + N) under conditions when only particles produced with a small total transverse momentum are observed. It is shown that in this case a number of amplitude combinations for the

+

N process can in principle be determined, one of them being the cross section for the non- polarized photon photoprocess ; the others enter the cross section for the photoprocess involving linearly polarized photons.

(*)

Nuclear Physics Institute, Novosibirsk (USSR).

Quasi-real electron method in high energy quantum electrodynamics

W-meson pair production in high energy electron collisions (*)

N. L. TER-ISAAKYAN and V. A. KHOZE Erevan Physics Institute (USSR)

Abstract.

Total cross sections for e* + e-

e' + ^e- + ^Wf + ^W-

processes are obtained in the asymptotic region of initial particle energies for cases when the anomalous magnetic moment of the W-meson is zero. The covariant formulation of the Weizsacker-Williams method, whose validity is ensured by ultrarelativism of the electrons, is employed. The asymptotic beha- vior of the e + + e-

W + + W- + ^p+ +

cross section is found.

V. N. BAIER, V. S. F A D I N , V. A. KHOZE

Abstract.

An electron pole approximation is presented, which can be used to calculate cross- sections in high energy quantum electrodynamics.

A general derivation is given and some applications are considered

1) bremsstrahlung in electron-elec- tron (positron) collisions at large angles

2) photo- production and electroproduction of a pair of particles on an electron at large angles ; 3) photon emission at a large angle when the cross-section does not decrease with energy

4) total cross-section for muon pair production in electron-positron collisions

(*)

Nuclear

cr

Equivalent photon approximation.

Range of validity, accuracy, etc.

V. M . BUDNEV, I. F. GINZBURG, G. V. MELEDIN, V. G . SERBO

Institute for Mathematics, Novosibirsk (USSR)

Abstract.

This review is devoted mainly to the two-photon production. We begin with a des- cription of- this method. The necessity of such an

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1974223

C2-122 CONTRIBUTIONS

introduction is, in particular, due to some errors or inaccurate statements when using this method in some papers, and too complicated formulas and methods used in other ones. Apart from the known formulas, a number of new results which are useful for experiment are provided, e. g. a simple and convenient method of estimation of the approximation accuracy. A special appendix is devoted to an analysis of a few errors and inaccurate statements contained in papers of Brodsky, Kinoshita and Terazawa (1970), Greco (1971), Cheng and Wu (19711, Bonneau, Gourdin and Martin (1972), etc.

cc

Hadron production

in electron-positron storage rings

a review

Institute for Mathematics, Novosibirsk (USSR)

Abstract.

This r.eview is devoted to the three general problems

1. Physics of the process y y

h (hadrons). 2. Methods of extracting the information on the process y y

h. 3. The other channels of the hadron production and background.

In the section concerning physics of the process

y y

h, we limit ourselves to a short consideration of

interesting reaction channels and domains of variables (photon

masses

and their summary energy) and review the principal theoretical ideas. The problem of extracting the information on the process y y

h is a central one in the review. Different versions of the experimental set-ups both associated with record- ing the scattered electrons and without it are consi- dered here in detail. The simple approximate expres- sions are obtained for corresponding contributions to the cross section. In conclusion, various sources of the background are listed and the corresponding estimates are given.

cc

The &-meson production in e + e--collisions

Institute for Mathematics, Novosibirsk (USSR)

Abstract.

Here a general solution of the dis- persion equation for the s-wave amplitude of the

y y

nn process has been obtained for the case

6(co)

n. An arbitrary constant of the solution is fixed by the PCAC requirement.

cc

Production of pion and muon pairs in e' e - colliding beams, going out of the limits

of equivalent photon approximation

Institute for Mathematics, Novosibirsk (USSR)

Abstract.

The reactions

e' e-

e' e- n + x-(/i+ c(-) are considered here in such a set-up, where only pions (muons) are recorded and k, total transverse momentum of the pair is not too small (roughly speaking rn: 4 k,

4 rn; ; this domain gives the main contribution to the cross section). In the paper the differential cross sections have been obtained with accuracy of ¹ k In -A . The amplitudes with the

tnn ( :?;I-:

one scalar photon have to be taken into account in this approximation. Besides, the charge asymmetry appears here due to the interference of the two- photon and bremsstrahlung diagrams. It is shown what information on the amplitudes of the reaction and the pion electromagnetic form factor can be obtained from experiment in the given set-up.

cr Quark parton model, light-cone expansions and virtual yy-scattering

V. L. CHERNYAK, V. G . SERBO Institute for Mathematics, Novosibirsk (USSR)

Abstract.

Here a model like that of Landshoff and Polkinghorne is presented. Within it a method is formulated which allows one for producing an arbitrary number of currents to obtain an expansion when one of the distances is small. The model is applied to the study of the forward yy-scattering in the region of deep virtuality of one of the photons :

q ,

9 tni, q: is arbitrary (q, and q2 are photon momenta)

( q l + q2)2

rn, -- 1 GeV .

For the absorptive part of the amplitude the following results have been obtained :

a) In the region mi s 4

q2/tn; the contri- bution of the box-diagram is dominant, and therefore amplitude is known. The eight independent invariant amplitudes of the process reduce to the two unknown functions in all the other cases. These last ones depend on two combinations of three independent variables s, q: and q: only.

b) In the region so - mi these combinations

are s/mi and (q:

q:)/(qI + ^{q : ) .}