**Light-Cone Path-Integral Approachto the LandauPomeranchukMigdal Effect*
**

**B. G. Zakharov**^{1)
}

Received November 27, 1997

**Abstract**—A new rigorous light-cone path-integral approach to the Landau–Pomeranchuk–Migdal effect in

QED and QCD is discussed. The rate of photon (gluon) radiation by an electron (quark) in a medium is

expressed in terms of the Green’s function of a two-dimensional Schrödinger equation with an imaginary poten-

tial. In QED, this potential is proportional to the dipole cross section for the scattering of a *e*^{+}*e*^{–} pair by an atom;

in QCD, it is proportional to the cross section for the interaction of a color-singlet quark–antiquark–gluon sys-

tem with a medium constituent. In QED, our predictions agree well with the photon spectrum measured recently

at SLAC for 25-GeV electrons. In QCD, for a sufficiently energetic quark produced inside a medium, we predict

the radiative energy loss *E*_{q} *L*^{2}, where *L* is the distance traveled by the quark in the medium. It has a weak

dependence on the initial quark energy *E*_{q}. The *L*^{2} dependence transforms into *L*^{1} as the quark energy decreases.

New formulas for nuclear shadowing in hard reactions are obtained.

Pleiades Publishing home page | journal home page | top

If you have any problems with this server, contact webmaster.