Transverse momentum distribution in hadrons: What can we learn from QCD?
- Physics Department, Southern Methodist University, Dallas, Texas 75275-0175 (United States)
We discuss some strict QCD constraints on the light-cone {pi} meson wave function {psi}({ital {rvec k}}{sub {perpendicular}}{sup 2},{ital x}). The analysis is based on such general methods as dispersion relations, duality, and partial conservation of axial-vector current. We calculate the asymptotic behavior of the wave function (WF) at the end-point region ({ital x}{r_arrow}1 and {ital {rvec k}}{sub {perpendicular}}{sup 2}{r_arrow}{infinity}) by analyzing the corresponding large {ital n}th moments in transverse {l_angle}{ital {rvec k}}{sub {perpendicular}}{sup 2{ital n}}{r_angle}{similar_to}{ital n}! and longitudinal {l_angle}(2{ital x}{minus}1){sup {ital n}}{r_angle}{similar_to}1/{ital n}{sup 2} directions. This information fixes the asymptotic behavior of the WF at large {ital {rvec k}}{sub {perpendicular}}{sup 2} (which turns out to be the Gaussian commonly used in phenomenological analyses). We discuss one particular application of the obtained results. We calculate the nonleading ``soft`` contribution to the pion form factor at intermediate momentum transfer. We argue that, due to the specific properties of {psi}({ital {rvec k}}{sub {perpendicular}}{sup 2},{ital x}), the corresponding contribution can temporarily {ital simulate} the leading twist behavior in the extent region of {ital Q}{sup 2}: 3 GeV{sup 2}{le}{ital Q}{sup 2}{le}40 GeV{sup 2}, where {ital Q}{sup 2}{ital F}({ital Q}{sup 2}){similar_to}const. Such a mechanism, if it is correct, would be an explanation of the phenomenological success of the dimensional counting rules at available, very modest energies for many different processes. We discuss some inclusive amplitudes (such as Drell-yan and deep inelastic) where the intrinsic {pi} meson structure might be essential. The relation to the valence quark model is also discussed.
- OSTI ID:
- 118563
- Journal Information:
- Physical Review, D, Vol. 52, Issue 9; Other Information: PBD: 1 Nov 1995
- Country of Publication:
- United States
- Language:
- English
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