236 research outputs found
The Impact of QCD and Light-Cone Quantum Mechanics on Nuclear Physics
We discuss a number of novel applications of Quantum Chromodynamics to
nuclear structure and dynamics, such as the reduced amplitude formalism for
exclusive nuclear amplitudes. We particularly emphasize the importance of
light-cone Hamiltonian and Fock State methods as a tool for describing the
wavefunctions of composite relativistic many-body systems and their
interactions. We also show that the use of covariant kinematics leads to
nontrivial corrections to the standard formulae for the axial, magnetic, and
quadrupole moments of nucleons and nuclei.Comment: 25 pages, uuencoded postscript file---To obtain a hard copy of this
paper, send e-mail to [email protected] and ask fo
Natural Color Transparency in High Energy (p,pp) Reactions
New parameter free calculations including a variety of necessary kinematic
and dynamic effects show that the results of BNL measurements are
consistent with the expectations of color transparency.Comment: latex file, 13 pages, 4 figures appended as ps files, look for "cut
here ..." 1993 Univ. of Washington preprint 404427-00-N93-1
Semi-Exclusive Processes: New Probes of Hadron Structure
We define and study hard ``semi-exclusive'' processes of the form which are characterized by a large momentum transfer between the particles
and and a large rapidity gap between the final state particle and
the inclusive system . Such reactions are in effect generalizations of deep
inelastic lepton scattering, providing novel currents which probe specific
quark distributions of the target at fixed momentum fraction. We give
explicit expressions for photo- and leptoproduction cross sections such as
in terms of parton distributions in the proton and the
pion distribution amplitude. Semi-exclusive processes provide opportunities to
study fundamental issues in QCD, including odderon exchange and color
transparency, and suggest new ways to measure spin-dependent parton
distributions.Comment: RevTex, 6 page
Color Coherent Phenomena with Hadron Beams
We outline major ideas involved in discussion of color coherence phenomena
(CCP) at intermediate energies. We point out that the recent advances in
calculating cross sections of hard exclusive processes off light nuclei allow
to use the lightest nuclei for sensitive tests of CCP. Consistency of the
results of the measurements of color transparency in quasielastic A(p,2p) and
A(e,ep) processes is emphasized. Evidence for presence of significant color
fluctuations in nucleons and pions emerging from the study of diffractive
processes is summarized. A new class of hard processes leading to three
particle final state is suggested for electron and hadron projectiles. A number
of new experiments are suggested to probe color fluctuations in hadrons.Comment: 14 pages,6 figures,Dedicated to Koichi Yazaki on the occasion of his
60th birthday. Invited talk at KEK-Tanashi International Symposium on Physics
of Hadrons and Nuclei, Tokyo, Japan, 14-17 Dec 199
Quantum Color Transparency and Nuclear Filtering
Color transparency is the proposal that under certain circumstances the
strong interactions can be reduced in magnitude. We give a comprehensive review
of the physics, which hinges on the interface of perturbative QCD with
non--perturbative strong interactions. Color transparency is complementary to
{\it nuclear filtering}, which is the conversion of quark wave functions in
hadrons to small transverse space dimensions by interaction with a nuclear
medium. We review current approaches, including pictures based on modeling the
time evolution of hadronic wave--packets as well as the use of light cone
matrix elements. Spin plays an intrinsic role in testing and understanding the
physics and is discussed at length. We emphasize the use of data analysis
procedures which have minimal model dependence. We also review existing
experimental data and the experimental program planned at various facilities.
The subject has strong scientific complementarity and potential to make
progress in exploring hadron physics at current and future facilities.Comment: 131 pages, review article in LaTeX to appear in Physics Reports, no
postscipt figures, approximately 30 figures available from Ralston on reques
Physics Opportunities at ELFE
I review some central physics opportunities at the 15 ... 30 GeV continuous
beam electron accelerator ELFE, proposed to be built in conjunction with the
DESY linear collider. Our present detailed knowledge of single parton
distributions in hadrons and nuclei needs to be supplemented by measurements of
compact valence quark configurations, accessible through hard exclusive
scattering, and of compact multiparton subsystems which contribute to
semi-inclusive processes. Cumulative (x>1, x_F>1) processes in nuclei measure
short-range correlations between partons belonging to different nucleons in the
same nucleus. The same configurations may give rise to subthreshold production
of light hadrons and charm.Comment: 16 pages, 3 figures included using epsf. (Misprint in Eq. (8)
corrected in revised version.
Color Transparency via Coherent Exclusive rho Production
We examine the potential of the COMPASS experiment at CERN to study color
transparency via exclusive coherent vector meson production in hard
muon-nucleus scattering. It is demonstrated that COMPASS has high sensitivity
to test this important prediction of perturbative QCD.Comment: Feasibility study for COMPASS collaboration, 3 pages, no figures, 1
table. This contribution is based on talk presented at the Workshop on Spin
Physics, Trento, Italy, July 2001. The conference www site is
http://ECTstar.ect.it/contents.html The proceedings of the workshop will be
published as a special issue of Nuclear Physics B (proc suppl), eds. S Bass,
A De Roeck and A Deshpande. A more complete 26 page feasibility study with 7
figures and 3 tables is available as A. Sandacz et al., hep-ex/0106076
Revision of 26 Sept. for Ref. 11 modificatio
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 reactions. The cross section
of hard 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 shifts
towards small values (), 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 reaction obtained from the EVA/AGS
experiment at Brookhaven National Laboratory. These data show -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.Comment: 30 pages LaTex file and 19 eps figure
Glauber theory of initial- and final-state interactions in (p,2p) scattering
We develop the Glauber theory description of initial- and final-state
interactions (IFSI) in quasielastic A(p,2p) scattering. We study the
IFSI-distortion effects both for the inclusive and exclusive conditions. In
inclusive reaction the important new effect is an interaction between the two
sets of the trajectories which enter the calculation of IFSI-distorted one-body
density matrix for inclusive (p,2p) scattering and are connected with
incoherent elastic rescatterings of the initial and final protons on spectator
nucleons. We demonstrate that IFSI-distortions of the missing momentum
distribution are large over the whole range of missing momentum both for
inclusive and exclusive reactions and affect in a crucial way the
interpretation of the BNL data on (p,2p) scattering. Our numerical results show
that in the region of missing momentum p_{m}\lsim 100-150 MeV/c the
incoherent IFSI increase nuclear transparency by 5-10\%. The incoherent IFSI
become dominant at p_{m}\gsim 200 MeV/c.Comment: Accepted in Z. Phys.A, Latex, 26 pages, uuencoded 9 figure
Extracting Nuclear Transparency from p-A Cross sections
We study nuclear structure effects on the transparency in high transverse
momentum and reactions. We show that in the DWIA-eikonal
approximation, even when correlations are included, one can get a factorized
expression for the transparency. This depends only on the average nucleon
density and a correlation function. We develop a technique to include
correlations in a Monte-Carlo Glauber type calculation. We compare calculations
of using the eikonal formalism and a continuous density, with a Monte Carlo
method based on discrete nucleons.Comment: 22 pages, 9 postscript figures. LaTeX with epsf styl
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