arXiv subjects

M. Sargsian

Publications and source records attributed to M. Sargsian.

25 records · Page 2Linked to original sources

arXiv2003

Hard Photodisintegration of a Proton Pair in 3He

Hard photodisintegration of the deuteron has been extensively studied in order to understand the dynamics of the transition from hadronic to quark-gluon descriptions of the strong interaction. In this work, we discuss the extension of this program to hard photodisintegration of a $pp$ pair in the $^3$He nucleus. Experimental confirmation of new features predicted here for the suggested reaction would advance our understanding of hard nuclear reactions. A main prediction, in contrast with low-energy observations, is that the $pp$ breakup cross section is not much smaller than the one for $pn$ break up.In some models, the energy-dependent oscillations observed for $pp$ scattering are predicted to appear in the $γ^3{\rm He} \to p p + n$ reaction. Such an observation would open up a completely new field in studies of color coherence phenomena in hard nuclear reactions. We also demonstrate that, in addition to the energy dependence, the measurement of the light-cone momentum distribution of the recoil neutron provides an independent test of the underlying dynamics of hard disintegration.

nucl-th↗

arXiv2002

Investigation of the high momentum component of nuclear wave function using hard quasielastic A(p,2p)X reactions

We present theoretical analysis of the first data on the high energy and momentum transfer (hard) quasielastic $C(p,2p)X$ reactions. The cross section of hard $A(p,2p)X$ reaction is calculated within the light-cone impulse approximation based on two-nucleon correlation model for the high-momentum component of the nuclear wave function. The nuclear effects due to modification of the bound nucleon structure, soft nucleon-nucleon reinteraction in the initial and final states of the reaction with and without color coherence have been considered. The calculations including these nuclear effects show that the distribution of the bound proton light-cone momentum fraction $(α)$ shifts towards small values ($α< 1$), effect which was previously derived only within plane wave impulse approximation. This shift is very sensitive to the strength of the short range correlations in nuclei. Also calculated is an excess of the total longitudinal momentum of outgoing protons. The calculations are compared with data on the $C(p,2p)X$ reaction obtained from the EVA/AGS experiment at Brookhaven National Laboratory. These data show $α$-shift in agreement with the calculations. The comparison allows also to single out the contribution from short-range nucleon correlations. The obtained strength of the correlations is in agreement with the values previously obtained from electroproduction reactions on nuclei.

nucl-th↗

arXiv1998

Coherent Vector Meson Production from Deuterons

In this paper we discuss coherent photo- and leptoproduction of vector mesons from deuterons at intermediate (virtual) photon energies, 3 < nu < 30 GeV. We consider the scattering from unpolarized and polarized targets as well as processes where the polarization of the recoil deuteron is measured. Our main motivation results from the need for a quantitative analysis of the space-time structure of photon-induced processes. In this respect we suggest several possibilities to explore the characteristic longitudinal interaction length in coherent vector meson production. Furthermore, we outline methods for an investigation of color coherence effects. In addition to the presentation of benchmark values for the maximal possible color coherence effect in various kinematic regions, we illustrate the anticipated phenomena within the color diffusion model. Finally we recall that the determination of vector meson-nucleon cross sections is not a closed issue. Besides being not known to a satisfying accuracy, they can be used to determine the strength of the D-state in low mass vector mesons.

nucl-th↗

arXiv1997

Probing the Origin of the EMC Effect via Tagged Structure Functions of the Deuteron

We demonstrate that measurement of tagged structure functions of the deuteron in (e,e'N) semi-inclusive reactions can discriminate between different hypotheses on the origin of the nuclear EMC effect. By choosing extreme backward kinematics for the spectator nucleon to minimize effects from the deuteron wave function and final state interactions, one can isolate the modifications in the structure of the bound nucleon within the impulse approximation. The same reaction can be used to extract the large-x neutron to proton structure function ratio.

nucl-th↗

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

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↗