182 research outputs found
A-dependence of hadronization in nuclei
The A-dependence of models for the attenuation of hadron production in
semi-inclusive deep-inelastic scattering on a nucleus is investigated for
realistic matter distributions. It is shown that the dependence for a pure
partonic (absorption) mechanism is more complicated than a simple
() behavior, commonly found when using rectangular or Gaussian
distributions, but that the A-dependence may still be indicative for the
dominant mechanism of hadronization.Comment: 4 pages, 4 figure
Doprinosi dodatnih raspršenja međudjelovanju u konačnom stanju u (e, e ˇ ′p) reakcijama
A semiclassical model is employed to study the effects of rescattering on (e,e˘p) cross sections. We consider a two-step process with the propagation of an intermediate nucleon and use Glauber theory to account for the effects of N-N scattering. This calculation has relevance for the analysis of data at high missing energies. Of particular interest is the E97-006 experiment done at JLab. It is found that rescattering is strongly reduced in parallel kinematics and that the excitation of nucleon resonances is likely to give important contributions to the final-state interactions in the correlated region.Primjenjujemo poluklasičan model za proučavanje učinaka dodatnih raspršenja u udarnim presjecima reakcija (e,e′p). Razmatramo dvostruki proces s gibanjem međunukleona, a učinke N–N raspršenja uključujemo prema Glauberovoj teoriji. Ovi su računi važni za analize podataka pri velikim manjkovima energije. Posebno je zanimljivo mjerenje E97-006 u JLaboratoriju. Nalazimo jako smanjenje dodatnih raspršenja u usporednoj kinematici te vjerojatno velike doprinose od uzbude nukleonskih rezonancija međudjelovanju u konačnom stanju u koreliranom području
Doprinosi dodatnih raspršenja međudjelovanju u konačnom stanju u (e, e ˇ ′p) reakcijama
A semiclassical model is employed to study the effects of rescattering on (e,e˘p) cross sections. We consider a two-step process with the propagation of an intermediate nucleon and use Glauber theory to account for the effects of N-N scattering. This calculation has relevance for the analysis of data at high missing energies. Of particular interest is the E97-006 experiment done at JLab. It is found that rescattering is strongly reduced in parallel kinematics and that the excitation of nucleon resonances is likely to give important contributions to the final-state interactions in the correlated region.Primjenjujemo poluklasičan model za proučavanje učinaka dodatnih raspršenja u udarnim presjecima reakcija (e,e′p). Razmatramo dvostruki proces s gibanjem međunukleona, a učinke N–N raspršenja uključujemo prema Glauberovoj teoriji. Ovi su računi važni za analize podataka pri velikim manjkovima energije. Posebno je zanimljivo mjerenje E97-006 u JLaboratoriju. Nalazimo jako smanjenje dodatnih raspršenja u usporednoj kinematici te vjerojatno velike doprinose od uzbude nukleonskih rezonancija međudjelovanju u konačnom stanju u koreliranom području
The He Cross Section at Large Missing Energy
The reaction on nuclei was studied in kinematics
designed to emphasize effects of nuclear short-range correlations. The measured
cross sections display a peak in the kinematical regions where two-nucleon
processes are expected to dominate. Theoretical models incorporating
short-range correlation effects agree reasonably with the data.Comment: 4 pages LaTeX, using espcrc1.sty and wrapfig.sty (included), two
figures. Talk presented by J. Templon at the 15th Int. Conf. on Few-Body
Problems in Physics, Groningen, The Netherlands, 22-26 July, 199
A consistent analysis of (e,e'p) and (d,3He) experiments
The apparent discrepancy between spectroscopic factors obtained in (e,e'p)
and (d,3He) experiments is investigated. This is performed first for
48Ca(e,e'p) and 48Ca(d,3He) experiments and then for other nuclei. It is shown
that the discrepancy disappears if the (d,3He) experiments are re-analyzed with
a non-local finite range DWBA analysis with a bound-state wave function that is
obtained from (e,e'p) experiments.Comment: 23 pages, 7 figure
Validity of the distorted-wave impulse-approximation description of CaK data using only ingredients from a nonlocal dispersive optical model
The nonlocal implementation of the dispersive optical model (DOM) provides
all the ingredients for distorted-wave impulse-approximation (DWIA)
calculations of the reaction. It provides both the overlap function,
including its normalization, and the outgoing proton distorted wave. This
framework is applied to describe the knockout of a proton from the
and orbitals in Ca
with fixed normalizations of 0.71 and 0.60, respectively. Data were obtained in
parallel kinematics for three outgoing proton energies: 70, 100, and 135 MeV.
Agreement with the data is as good as, or better than, previous descriptions
employing local optical potentials and overlap functions from Woods-Saxon
potentials - both with standard nonlocality corrections - whose normalization
(spectroscopic factor) and radius were fitted to the data. The present analysis
suggests that slightly larger spectroscopic factors are obtained when nonlocal
optical potentials are employed than those generated with local potentials. The
results further suggest that the chosen kinematical window around 100 MeV
proton energy provides the best and cleanest method to employ the DWIA for the
analysis of this reaction. The conclusion that substantial ground-state
correlations cannot be ignored when describing a closed-shell atomic nucleus is
therefore confirmed in detail. To reach these conclusions, it is essential to
have a complete description of the nucleon single-particle propagator that
accounts for all elastic nucleon-scattering observables in a wide energy domain
up to 200 MeV. The current nonlocal implementation of the DOM fulfills this
requirement.Comment: 15 pages, 11 figure
Effect of kinematics on final state interactions in (e,e'p) reactions
Recent data from experiment E97-006 at TJNAF using the 12C(e,e'p) reaction at
very large missing energies and momenta are compared to a calculation of
two-step rescattering.
A comparison between parallel and perpendicular kinematics suggests that the
effects of final state interactions can be strongly reduced in the former case.Comment: 10 pages, 3 figures, submitted to LP
Single particle strength restoration and nuclear transparency in high Q^2 exclusive (e,e'p) reactions
Quenching of the single particle strength which previously precluded
unambiguous measurement of nuclear transparency in quasifree (e,e'p) reactions
at high momentum transfer is evaluated from the cross sections of measured
processes. We have demonstrated evidence of the single particle strength
restoration with increase of the momentum transfer in exclusive (e,e'p)
reactions and argue that in practically interesting cases of study the nuclear
transparency in these processes quenching is weakly depends on the probability
of short range nucleon correlations. It is shown that use of Glauber
approximation well describes NE18 and E94-139 (e,e'p) data at the momentum
transfers 1 GeV^2 < Q^2 < 3 GeV^2. This gives a further support to our
observation that the quenching of nuclear levels strongly depends on the
resolution (Q^2)and practically disappears at Q^2>1GeV^2.Comment: 15 pages, 5 figures; references added, discussion extende
Nuclear structure studies with the 7Li(e,e'p) reaction
Experimental momentum distributions for the transitions to the ground state
and first excited state of 6He have been measured via the reaction
7Li(e,e'p)6He, in the missing momentum range from -70 to 260 MeV/c. They are
compared to theoretical distributions calculated with mean-field wave functions
and with variational Monte Carlo (VMC) wave functions which include strong
state-dependent correlations in both 7Li and 6He. These VMC calculations
provide a parameter-free prediction of the momentum distribution that
reproduces the measured data, including its normalization. The deduced summed
spectroscopic factor for the two transitions is 0.58 +/- 0.05, in perfect
agreement with the VMC value of 0.60. This is the first successful comparison
of experiment and ab initio theory for spectroscopic factors in p-shell nuclei.Comment: 4 pages, 3 figure
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