# Exclusive processes in perturbative quantum chromodynamics

## Abstract

We present a systematic analysis in perturbative quantum chromodynamics (QCD) of large-momentum-transfer exclusive processes. Predictions are given for the scaling behavior, angular dependence, helicity structure, and normalization of elastic and inelastic form factors and large-angle exclusive scattering amplitudes for hadrons and photons. We prove that these reactions are dominated by quark and gluon subprocesses at short distances, and thus that the dimensional-counting rules for the power-law falloff of these amplitudes with momentum transfer are rigorous predictions of QCD, modulo calculable logarithmic corrections from the behavior of the hadronic wave functions at short distances. These anomalous-dimension corrections are determined by evolution equations for process-independent meson and baryon ''distribution amplitudes'' phi(x/sub i/,Q) which control the valence-quark distributions in high-momentum-transfer exclusive reactions. The analysis can be carried out systematically in powers of ..cap alpha../sub s/(Q/sup 2/), the QCD running coupling constant. Although the calculations are most conveniently carried out using light-cone perturbation theory and the light-cone gauge, we also present a gauge-independent analysis and relate the distribution amplitude to a gauge-invariant Bethe-Salpeter amplitude.

- Authors:

- Publication Date:

- Research Org.:
- Laboratory of Nuclear Studies, Cornell University, Ithaca, New York 14853

- OSTI Identifier:
- 6804368

- Alternate Identifier(s):
- OSTI ID: 6804368

- DOE Contract Number:
- DE-AC03-76SF00515

- Resource Type:
- Journal Article

- Journal Name:
- Phys. Rev., D; (United States)

- Additional Journal Information:
- Journal Volume: 22:9

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; HADRONS; ELASTIC SCATTERING; INELASTIC SCATTERING; PHOTONS; QUANTUM CHROMODYNAMICS; EXCLUSIVE INTERACTIONS; BETHE-SALPETER EQUATION; FORM FACTORS; GAUGE INVARIANCE; GLUONS; HELICITY; LIGHT CONE; MOMENTUM TRANSFER; PERTURBATION THEORY; QUARKS; SCALING LAWS; SCATTERING AMPLITUDES; AMPLITUDES; ELEMENTARY PARTICLES; EQUATIONS; FIELD THEORIES; INTERACTIONS; INVARIANCE PRINCIPLES; MASSLESS PARTICLES; PARTICLE INTERACTIONS; PARTICLE PROPERTIES; POSTULATED PARTICLES; QUANTUM FIELD THEORY; SCATTERING; SPACE-TIME 645400* -- High Energy Physics-- Field Theory; 645202 -- High Energy Physics-- Particle Interactions & Properties-Theoretical-- Electromagnetic Interactions & Properties; 645204 -- High Energy Physics-- Particle Interactions & Properties-Theoretical-- Strong Interactions & Properties

### Citation Formats

```
Lepage, G.P., and Brodsky, S.J.
```*Exclusive processes in perturbative quantum chromodynamics*. United States: N. p., 1980.
Web. doi:10.1103/PhysRevD.22.2157.

```
Lepage, G.P., & Brodsky, S.J.
```*Exclusive processes in perturbative quantum chromodynamics*. United States. doi:10.1103/PhysRevD.22.2157.

```
Lepage, G.P., and Brodsky, S.J. Sat .
"Exclusive processes in perturbative quantum chromodynamics". United States. doi:10.1103/PhysRevD.22.2157.
```

```
@article{osti_6804368,
```

title = {Exclusive processes in perturbative quantum chromodynamics},

author = {Lepage, G.P. and Brodsky, S.J.},

abstractNote = {We present a systematic analysis in perturbative quantum chromodynamics (QCD) of large-momentum-transfer exclusive processes. Predictions are given for the scaling behavior, angular dependence, helicity structure, and normalization of elastic and inelastic form factors and large-angle exclusive scattering amplitudes for hadrons and photons. We prove that these reactions are dominated by quark and gluon subprocesses at short distances, and thus that the dimensional-counting rules for the power-law falloff of these amplitudes with momentum transfer are rigorous predictions of QCD, modulo calculable logarithmic corrections from the behavior of the hadronic wave functions at short distances. These anomalous-dimension corrections are determined by evolution equations for process-independent meson and baryon ''distribution amplitudes'' phi(x/sub i/,Q) which control the valence-quark distributions in high-momentum-transfer exclusive reactions. The analysis can be carried out systematically in powers of ..cap alpha../sub s/(Q/sup 2/), the QCD running coupling constant. Although the calculations are most conveniently carried out using light-cone perturbation theory and the light-cone gauge, we also present a gauge-independent analysis and relate the distribution amplitude to a gauge-invariant Bethe-Salpeter amplitude.},

doi = {10.1103/PhysRevD.22.2157},

journal = {Phys. Rev., D; (United States)},

number = ,

volume = 22:9,

place = {United States},

year = {1980},

month = {11}

}