arXiv subjects

L. Frankfurt

Publications and source records attributed to L. Frankfurt.

103 records · Page 6Linked to original sources

arXiv1997

Coherent Photo- and Leptoproduction of Vector Mesons from Deuterium

We discuss the coherent photo- and leptoproduction of vector mesons from deuterium at intermediate (virtual) photon energies, 3 GeV < nu < 30 GeV. These processes provide several options to explore the space-time evolution of small size quark-gluon configurations. Furthermore, we study the dependence of the production cross section on the energy and momentum transfer t due to variations of the finite longitudinal interaction length. Kinematic regions are determined where the production cross section is most sensitive to the final state interaction of the initially produced hadronic wave packet. For unpolarized deuteron targets this double scattering contribution can be investigated mainly at large values of the momentum transfer t. For polarized targets kinematic windows sensitive to double scattering are available also at moderate t. We suggest several methods for an investigation of color coherence effects at intermediate energies.

hep-ph↗

arXiv1996

Interaction of small size wave packet with hadron target

We calculate in QCD the cross section for the scattering of an energetic small-size wave packet off a hadron target. We use our results to study the small-$σ$ behaviour of $P_π(σ)$, the distribution over cross section for the pion, in the leading $α_{s}$-order.

hep-ph↗

arXiv1996

Coherent $ρ$ Production from Polarized Deuterium

We discuss the coherent leptoproduction of vector mesons from polarized deuterium as a tool to investigate the evolution of small size quark-gluon configurations. Kinematic regions are determined where the final state interaction of the initially produced quark-gluon wave packet contributes dominantly to the production cross section. Two methods for an investigation of color coherence effects, which are appropriate for future experiments at HERMES, are suggested.

hep-ph↗

arXiv1996

Nearthreshold Large $Q^2$ Electroproduction off Polarized Deuteron

The exclusive and inclusive electroproduction off the polarized deuteron is considered at large $Q^2$ and $x \ge 0.5$. It is shown that the use of a polarized target will allow to emphasize smaller than average internucleon distances in the deuteron. As a result, we expect amplification of all the effects (color transparency, relativistic dynamics, etc.) sensitive to small internucleon distances. Numerical estimates are given for the processes $e+ \vec d \rightarrow e +p+n$ and $e+ \vec d \rightarrow e +X$.

nucl-th↗

arXiv1996

Color Transparency and Color Opacity in Coherent Production of Vector Mesons off Light Nuclei at small x

Coherent electroproduction of vector mesons off $^2$H and $^4$He is considered in the kinematics of deep inelastic scattering. Special emphasis is given to the $-t\sim 0.8-1$ GeV$^2$ region where the cross section is dominated by the interaction of the $q\bar q$ configuration in the $γ^*$ with two nucleons. These kinematics provide the unique possibilities to study quantitatively in vector meson production the onset of Color Transparency with increasing $Q^2$ as well as its gradual disappearance at very small $x$, i.e., perturbative Color Opacity.

hep-ph↗

arXiv1996

Chiral Transparency

Color transparency is the vanishing of initial and final state interactions, predicted by QCD to occur in high momentum transfer quasielastic nuclear reactions. For specific reactions involving nucleons, the initial and final state interactions are expected to be dominated by exchanges of pions. We argue that these interactions are also suppressed in high momentum transfer nuclear quasielastic reactions; this is ``chiral transparency". We show that studies of the $e ^3He \to e'Δ^{++} nn$ reaction could reveal the influence of chiral transparency.

nucl-th↗

arXiv1996

The nuclear effects in $g_{1^3\rm{He}}$ and the Bjorken sum rule for A=3

The Bjorken sum rules for the $A=3$ and $A=1$ are used as a guide to estimate nuclear effects in extracting $g_{1n}(x,Q^{2})$ from the $\vec{e}\,\vec{^3\rm{He}}$ data. We estimate that the combination of the spin depolarization, the nonnucleonic degrees of freedom in the $A=3$ system and nuclear shadowing is likely to reduce $g_{1^3\rm{He}}(x\le 0.05)$ by $\sim 15 \%$ while a significant enhancement of the structure functions $g_{1^3\rm{He}}, g_{1^3\rm{H}}$ at $x \sim 0.1$ is predicted.

hep-ph↗

arXiv1994

Probing Short Range Nucleon Correlations in High Energy Hard Quasielastic pd Reactions

We show that the strong dependence of the amplitude for $NN$ hard scattering on the collision energy can be used to magnify the effects of short range nucleon correlations in quasielastic $pd$ scattering. Under specific kinematical conditions the effect of initial and final state interactions can be accounted for by rescaling the cross section calculated within the plane wave impulse approximation. The feasibility to investigate the role of relativistic effects in the deuteron wave function is demonstrated by comparing the predictions of different formalisms. Binding effects due to short range correlations in deuteron are discussed as well.

nucl-th↗

arXiv1994

Diffractive Leptoproduction of Vector Mesons in QCD

We demonstrate that the distinctive features of the forward differential cross section of diffractive leptoproduction of a vector meson can be legitimately calculated in perturbative QCD in terms of the light-cone $q \bar q$ wave function of the vector meson and the gluon distribution of the target. In particular, we calculate the $Q^2$ and nuclear dependence of the diffractive leptoproduction of vector mesons and estimate the cross section. The production of longitudinally polarized vector mesons by longitudinally polarized virtual photons is predicted to be the dominant component, yielding a cross section behaving as $Q^{-6}$. The nuclear dependence of the diffractive cross sections, which follows from a factorization theorem in perturbative QCD, provides important tests of color transparency as well as constraints on the shadowing of the gluon structure functions and the longitudinal structure functions of nuclei.

hep-ph↗

arXiv1994

Searching for Color Coherent Effects at Intermediate $Q^2$ via Double Scattering Processes

We propose that measuring the $Q^2$ dependence of the number of final-state interactions of the recoil protons in quasi-elastic electron scattering from light nuclei is a new method to investigate Color Coherent effects at {\bf intermediate} values of $Q^2$ ({$\sim$ few $(GeV/c)^2$}). This is instead of measuring events without final-state interactions. Our calculations indicate that such measurements could reveal significant color transparency effects for the highest of the energies initially available at CEBAF. Measurements that detect more than one hadron in the final state, which require the use of large acceptance ($4π$) detectors, are required.

nucl-th↗

arXiv1993

Evidence for Color Fluctuations in Hadrons from Coherent Nuclear Diffraction}

A QCD-based treatment of projectile size fluctuations is used to compute inelastic diffractive cross sections $σ_{diff}$ for coherent hadron-nuclear processes. We find that fluctuations near the average size give the major contribution to the cross section with $ \le few \%$ contribution from small size configurations. The computed values of $σ_{diff}$ are consistent with the limited available data. The importance of coherent diffraction studies for a wide range of projectiles for high energy Fermilab fixed target experiments is emphasized. The implications of these significant color fluctuations for relativistic heavy ion collisions are discussed.

hep-ph↗

arXiv1993

Coherent Nuclear Diffractive Production of Minijets - Illuminating Color Transparency

The cross section for coherent nuclear processes in which an incident meson or photon dissociates diffractively into two jets of high relative transverse momentum (between about 1 and 3 GeV/c) is found to be proportional in QCD to $A^2$ in a wide kinematical region. The leading correction to this is a significant positive term $\propto A^{7/3}$ caused by nuclear multiple-scattering. We find also that shadowing of hard diffractive processes reappears as a leading twist effect in the TeV energy range.

hep-ph↗

arXiv1992

Sum Rule Description of Color Transparency

The assumption that a small point-like configuration does not interact with nucleons leads to a new set of sum rules that are interpreted as models of the baryon-nucleon interaction. These models are rendered semi-realistic by requiring consistency with data for cross section fluctuations in proton-proton diffractive collisions.

nucl-th↗