Two-photon processes for particle production at high energies

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Submitted on 1 Jan 1974

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Two-photon processes for particle production at high energies

H. Terazawa

To cite this version:

H. Terazawa. Two-photon processes for particle production at high energies. Journal de Physique

Colloques, 1974, 35 (C2), pp.C2-123-C2-124. �10.1051/jphyscol:1974232�. �jpa-00215542�

CONTRIBUTIONS C2-123

c ) In the region s 2 q: q;/rn; these combinations The two-photon process for particle ~roduction

are s/q: and qZ/mi. in colliding beam experiments (*)

At qZ/rn% 9 1 the dependence on only argument G . GRAMMER, Jr. and T. KINOSHITA mi/q: qZ is left and at sm;/q: 9; 9 the Regge

Laboratory of Nuclear Studies, Cornell University,

behaviour takes place. Ithaca, New York 14850, USA

Abstract. - A comparison is made, for various.

two-photon processes (ee

eez

, eepf p-, eezf z-), between an exact calculation on the one hand and two alternative forms of the equivalent photon approximation (namely, the Low formula and the

<< Two-photon production

Dalitz-Yennie formula) on the other hand. Angular of leptons and search of new particles n

distributions of the particles produced are consi- V. M. BUDNEV, I. F. GINZBURG, dered, as well as total cross sections.

G . V. MELEDIN, V. G. SERBO

Institute for Mathematics, Novosibirsk (USSR) Abstract. -This review is devoted to the following problems :

1. Some little-known applications and effects con- nected with the two-photon e + e--pair production : energy losses of fast muons in the matter ; the investigation of

and K form factors ; the possi- bility to calibrate accelerators with the colliding pp, pp or ep beams ; measuring the high energy photon polarization, measuring the real part of pro- ton Compton effect, etc.

2. Some processes of high order in cr for the electron storage rings having cross section high enough, two e f e--pair production (ee

eee' e - e f e-) ; parapositronium production ; production of pho- tons with MeV energy for large emission angles.

3. The search of new particles : intermediate vector mesons, Dirac's monopols and massive leptons.

4. Some questions of the two-photon massive p-pair production.

Parton model for scattering L. I. PERLOVSKY and E. P. HEIFEZ Institute for Mathematics, Novosibirsk (USSR) Abstract. - The parton model for the process yy into hadrons is considered. The total cross section in the kinematic region s + ^{( q:} 1, ⁽ q: I + ^{I GeV2}

is obtained to be a function of a single variable :

2 2

a,, = q(s/q, q2), s = 2 q l q,, 61. q2 - the photons, 4-momenta.

Corrections to equivalent photon approximation for two-photon processes in colliding beams (*)

K . SUBBARAO

Joseph-Henry Laboratories, Princeton University, Princeton, New Jersey 08540, USA

and

Laboratory of Nuclear Studies, Cornell University, Ithaca, New York 14850, USA (**)

Abstract. - The cross section for the two-photon process ee

e e r in colliding electron beams, in the limit E

co with E 2 / s fixed (E being the energy per beam of the colliding electrons of mass m, and

4s the invariant mass of the state r ) is well known to have a leading term of order (In 4 E2/~7~2)2. This leading term is given correctly by the well-known Weizsacker-Williams approximation or the equi- valent photon approximation. There are sizeable corrections coming from non-leading terms of which the first one, namely, the term of order (In 4 ~'lrn') has been obtained for an arbitrary hadronic final state r. The approximations made in getting the Weizsacker-Williams result and the correction terms due to each of them have been exhibited.

Two-photon processes for particle production at high energies (*)

The Rockefeller University, New York, New York 10021, USA

Abstract. - The literature of the past three years on the two-photon process for particle production e' + e -

e' + y* + e- + y*

e' + e- + X

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1974232

C2-

CONTRIBUTIONS

(where X is any C ⁼ + state) or amplitudes ; subtractions have then been fixed impos- p + p + X 1 + y * + X 2 + y * - + X 1 + ing off-mass-shell current algebra limits both for one + x2 ^{+ y + + p-} and two massless external mesons. Predictions on the S wave amplitudes have also been derived from (where XI,

are hadron states) is reviewed in Some the recent analysis of meson-meson scattering by detail. Both the theoretical aspects and the experi- Protopopescu ol

mental feasibility of various processes are discussed especially for experimentalists' convenience.

The equivalent polarised-photon approximation Absorption of high-energy cosmic photons through

double pair production in photon-photon collisions R. W. BROWN and K. 0 . MIKAELIAN

Department of Physics, Case Western Reserve University,

Cleveland, Ohio 44106, USA and

Department of Physics, University of California at San Diego,

La Jolla, California 92037, USA Abstract. - At photon energies above

absorption by y + y'

2 ef + 2 e- dominates that from the lower-order process y + y'

ef + e- for high-energy photons traversing a 2.8 K blackbody photon gas. Existence of the 2 e f , 2 e- process and the cosmic blackbody radiation thus guarantees that the universe is opaque for all photon energies above l o t 4 eV. The question of single-pair production in collisions with cosmic radio-wave photons is discussed, and the uncertainty in our knowledge of the important low-frequency end of the radio spectrum is emphasized.

Other processes (y + ^y'

muons, hadrons, etc.) are discussed briefly, and it is concluded that they are of minor importance.

A treatment of meson pair production in yy collisions including inelasticity

and current algebra P. GENSINI

Istituto di Fisica dell'Universit8, Lecce Abstract.

We have considered two problems posed by dispersive approaches to yy

and yy

K K amplitudes, namely the introduction of inelastic unitarity and the ambiguity in partial wave dispersion relation subtractions. Introducing an (R, 9) representation for nn amplitudes, we have transformed inelastic unitarity into an inhomogeneous Hilbert- Riemann problem, completely defined by one subtrac- tion and by the knowledge of meson-meson partial

C. J. BROWN and D. H. LYTH University of Lancaster,

Department of Physics, Lancaster, U K

Abstract. - The equivalent photon approximation is studied for the case where the scattered electron is detected. The equivalent photon is then polarised.

The region of validity is found t o depend on the virtual photon scattering angle, rather than on the electron scattering angle, and this distinction is important. A discrepancy concerning the dependence on beam energy of the total cross section for ee

e e +

hadrons which was noted by Bonneau et al. is resolved.

Particular cases of particle production in inelastic lepton

(anti) lepton scattering G. BONNEAU and F. MARTIN Laboratoire de Physique ThCorique et des Hautes Energies, Paris, France

Abstract.

As in a previous paper we consider the inclusive reactions e + e

e + e + anything in the two photon exchange approximation. We present the complete calculation of the differential cross section da/d W2 for the production of a state of effective mass Wand we give the expression of the total cross section.

We apply this to the muon pair and the pseudoscalar meson (no, q and q ' ) productions.

A suggestion for investigating electron-muon and electron-pion scattering with electron-positron colliding beams C. CARIMALO, P. KESSLER and J. PARISI

Laboratoire de Physique Atomique, Colli.ge de France, Paris, France

Abstract.

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 f colliding

beam experiment where one large-angle electron and

one large-angle muon or pion would be measured