arXiv subjects

M. Strikman

Publications and source records attributed to M. Strikman.

226 records · Page 13Linked to original sources

arXiv1995

The Nucleon's Virtual Meson Cloud and Deep Inelastic Lepton Scattering

We address the question whether the nucleon's antiquark sea can be attributed entirely to its virtual meson cloud and, in essence, whether there exists a smooth transition between hadronic and quark-gluon degrees of freedom. We take into account contributions from $π$ and $K$ mesons and compare with the nucleon's antiquark distributions which serve as a non-perturbative input to the QCD evolution equations. We elucidate the different behavior in the flavor singlet and non-singlet channels and study the dependence of our results on the scale $Q^2$. The meson-nucleon cut-offs that we determine give not only an indication on the size of the region within which quarks are confined in a nucleon, but we find that the scale of these form factors is closely related to the four-momentum transfer, $Q^2$, where gluons are resolved by a high energy probe, and that large meson loop momenta, $|{\bf k}| \approx 0.8$ GeV, contribute significantly to the sea quark distributions. While the agreement of our calculations with data-based parametrizations is satisfactory and scale independent for the flavor breaking share of the nucleon's antiquark sea, the flavor singlet component is quite poorly described. This hints the importance of gluon degrees of freedom.

hep-ph↗

arXiv1995

Hadronic cross-section fluctuations and proton coherent diffractive dissociation on helium

The differential cross-section of inelastic coherent diffractive dissociation off nuclei $p~+~^4$He $\rightarrow X ~+ ~^4$He is expressed in terms of the relative cumulants of the cross-section distribution $P_N(σ)$. The theoretical result for the ratio $r=\Bigg(\frac{dσ_{diff}}{dt}\Bigg)^{pHe}_{t=0} \Bigg/ \Bigg(\frac{dσ_{diff}}{dt}\Bigg)^{pp}_{t=0}=6.8 ÷7.6$ is close to the value $r=7.1 \pm 0.75$ which we extracted from the FNAL data. These are the only $A>2$ data of this kind. The comparison provides the first confirmation of the cross-section fluctuation approach to the description of the absolute value of the inelastic diffraction cross-section off nuclei. It provides also a new constraint on the first 4 cumulants of the cross-section distribution.

nucl-th↗

arXiv1995

Correlations and Fluctuations in High-Energy Nuclear Collisions

Nucleon correlations in the target and projectile nuclei are shown to reduce significantly the fluctuations in multiple nucleon-nucleon collisions, total multiplicity and transverse energy in relativistic heavy-ion collisions, in particular for heavy projectile and target. The interplay between cross-section fluctuations, from color transparency and opacity, and nuclear correlations is calculated and found to be able to account for large fluctuations in transverse energy spectra. Numerical implementation of correlations and cross-section fluctuations in Monte-Carlo codes is discussed.

nucl-th↗

arXiv1994

The Geometrical Color Optics Of Coherent High Energy Processes

CONTENTS. 1.Introduction, 1.1 QCD ideas to be tested; 2. Coherence phenomena in QED, 2.1 Charge transparency, 2.2 Charge filtering, 2.3 Charge opacity; 3. Color transparency in perturbative QCD, 3.1 Coherence length in QCD, 3.2 Bjorken scaling for deep inelastic processes, 3.3 Hard Coherent Diffraction {}From Nucleons and Nuclei; 4. Soft Diffractive Physics and Color Fluctuations, 4.1 Scattering eigenstates formalism; 4.2 Current information on color fluctuations in Hadrons, 4.3 Small Size Configurations in Pions, 4.4 Nuclear inelastic diffraction as evidence for color fluctuations near the average value, 4.5 Inelastic screening corrections to the total cross sections; 5. Color transparency in nuclear quasielastic reactions. 5.1 Is a small system made?, 5.2 Time development, 5.3 Relevant data; 6. Color fluctuations in nucleons and nucleus-nucleus collisions, 6.1 Color opacity effects, 6.2 Color fluctuations and central collisions, 6.3 Leading hadron transparency effects in central collisions.

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↗