arXiv subjects

V. R. Zoller

Publications and source records attributed to V. R. Zoller.

63 records · Page 4Linked to original sources

arXiv1995

Exclusive high-$Q^2$ electroproduction: light-cone wave functions and electromagnetic form factors of mesons,

We apply the light-cone technique to electroproduction reaction $ep\to eπ^+n$ long considered as a means of measuring the electromagnetic form factor of the pion. We show that the interpretation of the long-standing puzzle of large transverse cross section ($σ_T$) in terms of the $γ^*ρ\to π$ transition on the $ρ$ mesons in the light-cone proton is possible, but requires quite a slow decrease of the $F_{ρπ}(\q2)$ form factor. This interpretation can be tested in the related $ep\to eπ^0p$ reaction. Corrections which are due to the final-state meson-baryon interactions (FSI) are evaluated and are shown to amount to a $25\%$ effect at moderately large $\q2$. Vanishing FSI with increasing $Q^2$ - the color transparency phenomenon - is shown to be very strong.

hep-ph↗

arXiv1994

The direct calculation of the slope of the QCD pomeron's trajectory

We demonstrate that the diffraction slope of the generalized BFKL pomeron amplitude has the conventional Regge growth $B(s) = B(0) + 2α_{\Pom}'\log(s)$. This proves that the generalized BFKL pomeron is described by the moving $j$-plane singularity. We give an estimate for the slope $α_{\Pom}'$ in terms of the correlation radius for the perturbative gluons.

hep-ph↗

arXiv1994

Why more hadronlike photons produce less particles on nuclear targets

In hadron-nucleus interactions, the stronger is nuclear shadowing in the total cross section the higher is the multiplicity of secondary hadrons. In deep inelastic scattering, nuclear shadowing at small $x$ is associated with the hadronlike behaviour of photons as contrasted to the pointlike behaviour in the non-shadowing region of large $x$. In this paper we predict smaller mean multiplicity of secondary hadrons, and weaker fragmentation of the target nucleus, in deep inelastic leptoptoproduction on nuclei in the shadowing region of small $x$ as compared to the non-shadowing region of large $x$. This paradoxial conclusion has its origin in nuclear enhancement of the coherent diffraction dissociation of photons. We present numerical predictions for multiproduction in $μXe$ interactions studied by the Fermilab E665 collaboration.

hep-ph↗

arXiv1994

The BFKL and GLDAP regimes for the perturbative QCD pomeron

The $S$-matrix of diffractive scattering is diagonalized in terms of the colour dipole-dipole cross section. Recently, we have shown that the dipole cross section satisfies the generalized BFKL equation. In this paper we discuss the spectrum and solutions of our generalized BFKL equation with allowance for the finite gluon correlation radius $R_{c}$. The latter is introduced in the gauge invariant manner. We present estimates of the intercept of the pomeron and find the asymptotic form of the dipole cross section. We consider the difference between the BFKL and GLDAP evolutions and conclude that the GLDAP evolution remains a viable description of deep inelastic scattering well beyond the kinematical range of the HERA experiments. We suggest methods of measuring the pomeron intercept in the HERA experiments.

hep-ph↗

arXiv1994

Theoretical Interpretation of the NE18 Experiment on Nuclear Transparency in A(e,e'p) Scattering

The spectral function, measured in $A(e,e'p)$ reactions, is distorted by the final-state interaction of the struck proton with the residual nucleus. This causes a broadening of the observed transverse-momentum distribution which is large even in the $d(e,e'p)$ reaction. We discuss the effects of this $p_{\perp}$-broadening on the nuclear transparency measured in the recent NE18 experiment. Within conventional Glauber theory we can describe the measurements. Transparency effects are thus small in agreement with our earlier predictions.

nucl-th↗

arXiv1994

The spectrum and solutions of the generalized BFKL equation for total cross section

The colour dipole cross section is the principal quantity in the lightcone $s$-channel description of the diffractive scattering. Recently we have shown that the dipole cross section satisfies the generalized BFKL equation. In this paper we discuss properties and solutions of our generalized BFKL equation with allowance for the finite gluon correlation radius $R_{c}$. The latter is introduced in a gauge invariant manner. We present estimates of the intercept of the pomeron and find the asymptotic form of the dipole cross section.

hep-th↗

arXiv1993

The $s$-channel approach to Lipatov's pomeron and hadronic cross sections

We derive a generalized Balitskii-Fadin-Kuraev-Lipatov equation, which applies directly to the perturbative QCD component of total cross section. With the gluon correlation radius $R_{c} \sim 0.4$f we reproduce the empirical rate of growth of the hadron-nucleon total cross sections. The simultaneous estimate of the triple-pomeron coupling also agrees with the experiment.

hep-ph↗

arXiv1993

Correlation Effects in the Final-State Interaction for Quasielastic $(e,e'p)$ Scattering

Color transparency predicts that, in $(e,e'p)$ reactions at large $Q^2$, the final-state interaction becomes weaker than the reference value predicted from the free-nucleon cross section. This reference value is usually evaluated in the dilute-gas approximation to Glauber's multiple-scattering theory. We derive the leading-order correction taking into account two-body correlations. Large cancellations are found so that the overall correlation effect is small.

nucl-th↗

arXiv1993

The Onset of Color Transparency in $(e,e'p)$ Reactions on Nuclei

Quantum filtering of the ejectile wave packet from hard $ep$ scattering on bound nucleons puts stringent constraints on the onset of color transparency in $(e,e'p)$ reactions in nuclei at moderate energies. Based on multiple-scattering theory, we derive a novel formula for nuclear transparency and discuss its energy dependence in terms of a color transparency sum rule.

nucl-th↗