482 research outputs found
Lepton Scattering off Few-Nucleon Systems at Medium and High Energies
The interpretation of recent Jlab experimental data on the exclusive process
A(e,e'p)B off few-nucleon systems are analyzed in terms of realistic nuclear
wave functions and Glauber multiple scattering theory, both in its original
form and within a generalized eikonal approximation. The relevance of the
exclusive process 4He(e,e'p)^3H for possible investigations of QCD effects is
illustrated.Comment: 6 pages, 3 figures. Plenary talk given by C. Ciofi degli Atti at the
XX European Conference "Few Body Problems in Physics", Pisa, Italy, September
2007. To appear in Few-Body System
A non factorized calculation of the process ^3He(e,e'p)^2H at medium energies
The exclusive process ^3He(e,e^\prime p)^2H has been analyzed using realistic
few-body wave functions corresponding to the AV18 interaction and treating the
final state interaction (FSI) within the Eikonal Approximation to describe the
multiple rescattering of the struck nucleon with the nucleons of the spectator
two-nucleon system. Calculations have been performed in momentum space so that
the nucleon electromagnetic current could be left in the fully covariant form
avoiding by this way non relativistic reductions and the factorization
approximation. The results of calculations, which are compared with recent JLab
experimental data, show that the left-right asymmetry exhibit a clear
dependence upon the multiple scattering in the final state and demonstrate the
breaking down of the factorization approximation at \phi=0 i.e. for "negative"
and large \geq 300MeV/c values of the missing momentum.Comment: 14 pages, 6 figure
On the effects of the final state interaction in the electro-disintegration of the deuteron at intermediate and high energies
The role of the final state interactions (FSI) in the inclusive quasi-elastic
disintegration of the deuteron is investigated treating the two-nucleon final
state within the exact continuum solutions of the non-relativistic Schroedinger
equation, as well as within the Glauber multiple scattering approach. It is
shown that for values of the Bjorken scaling variable both
approaches provide similar results, unless the case , where
they appreciably disagree. It is demonstrated that present experimental data,
which are mostly limited to a region of four-momentum transfer () where the Center-of-Mass energy of the final state is below the
pion threshold production, can be satisfactorily reproduced by the approach
based on the exact solution of the Schroedinger equation and not by the Glauber
approach. It is also pointed out that the latter, unlike the former, does not
satisfy the inelastic Coulomb sum rule, the violation being of the order of
about 20%.Comment: 16 LaTeX pages, 10 eps-figures, 1 tabl
Ground-state energies, densities and momentum distributions in closed-shell nuclei calculated within a cluster expansion approach and realistic interactions
A linked cluster expansion suitable for the treatment of ground-state
properties of complex nuclei, as well as of various particle-nucleus scattering
processes, has been used to calculate the ground-state energy, density and
momentum distribution of 16-O and 40-Ca using realistic interactions. First of
all, a benchmark calculation for the ground-state energy has been performed
using the truncated V8' potential, and consisting in the comparison of our
results with the ones obtained by the Fermi Hypernetted Chain approach,
adopting in both cases the same mean field wave functions and the same
correlation functions. The results exhibited a nice agreement between the two
methods. Therefore, the approach has been applied to the calculation of the
ground-state energy, density and momentum distributions of 16-O and 40-Ca using
the full V8' potential, finding again a satisfactory agreement with the results
based on more advanced approaches where higher order cluster contributions are
taken into account. It appears therefore that the cluster expansion approach
can provide accurate approximations for various diagonal and non diagonal
density matrices, so that it could be used for a reliable evaluation of nuclear
effects in various medium and high energy scattering processes off nuclear
targets. The developed approach can be readily generalized to the treatment of
Glauber type final state interaction effects in inclusive, semi-inclusive and
exclusive processes off nuclei at medium and high energies.Comment: 42 pages, 18 figure
Nuclear effects in Deep Inelastic Scattering of polarized electrons off polarized 3He and the neutron spin structure functions
It is shown that the nuclear effects playing a relevant role in Deep
Inelastic Scattering of polarized electrons by polarized He are mainly
those arising from the effective proton and neutron polarizations generated by
the and waves in He. A simple and reliable equation relating the
neutron, , and He, , spin structure functions is proposed. It
is shown that the measurement of the first moment of the He structure
function can provide a significant check of the Bjorken Sum Rule.Comment: 11 pages (revTeX), DFUPG 75/93; 5 (postscript) figures available upon
request from the author
Ground-state correlations and final state interactions in the process 3He(e,e'pp)n
The two-proton emission process is theoretically investigated
using realistic three-nucleon wave functions and taking the final state
interaction into account by an approach which can be used when the value of the
three-nucleon invariant mass is either below or above the pion emission
threshold. Various kinematical conditions which enhance or minimize the effects
of the final state interaction are thoroughly analyzed.Comment: 26 pages, 12 eps-figures. Introduction and abstract updated, few
references added and Apendix A remove
Calculations of the Exclusive Processes 2H(e,e'p)n, 3He(e,e'p)2H and 3He(e,e'p)(pn) within a Generalized Glauber Approach
The exclusive processes 2H(e,e'p)n, 3He(e,e'p)2H and 3He(e,e'p)(pn), have
been analyzed using realistic few-body wave functions and treating the final
state interaction (FSI) within a Generalized Eikonal Approximation (GEA), based
upon the direct calculation of the Feynman diagrams describing the rescattering
of the struck nucleon with the nucleons of the A-1 system. The approach
represents an improvement of the conventional Glauber approach (GA), in that it
allows one to take into account the effects of the nuclear excitation of the
system on the rescattering of the struck nucleon. Using realistic
three-body wave functions corresponding to the AV18 interaction, the results of
our parameter free calculations are compared with available experimental data.
It is found that in some kinematical conditions FSI effects represent small
corrections, whereas in other kinematics conditions they are very large and
absolutely necessary to provide a satisfactory agreement between theoretical
calculations and experimental data. It is shown that in the kinematics of the
experimental data which have been considered, covering the region of missing
momentum and energy with p_m < 0.6 GeV/c and E_m < 100 MeV in the perpendicular
kinematics, the GA and GEA predictions differ only by less than 3-4 %.Comment: Typos detected and removed while Proof reading. Physical Review C. in
Pres
Slow Proton Production in Semi-Inclusive Deep Inelastic Scattering off Deuteron and Complex Nuclei: Hadronization and Final State Interaction Effects
The effects of the final state interaction in slow proton production in semi
inclusive deep inelastic scattering processes off nuclei, A(e,e'p)X, are
investigated in details within the spectator and target fragmentation
mechanisms; in the former mechanism, the hard interaction on a nucleon of a
correlated pair leads, by recoil, to the emission of the partner nucleon,
whereas in the latter mechanism proton is produced when the diquark, which is
formed right after the visrtual photon-quark interaction, captures a quark from
the vacuum. Unlike previous papers on the subject, particular attention is paid
on the effects of the final state interaction of the hadronizing quark with the
nuclear medium within an approach based upon an effective time-dependent cross
section which combines the soft and hard parts of hadronization dynamics in
terms of the string model and perturbative QCD, respectively. It is shown that
the final state interaction of the hadronizing quark with the medium plays a
relevant role both in deuteron and complex nuclei; nonetheless, kinematical
regions where final state interaction effects are minimized can experimentally
be selected, which would allow one to investigate the structure functions of
nucleons embedded in the nuclear medium; likewise, regions where the
interaction of the struck hadronizing quark with the nuclear medium is
maximized can be found, which would make it possible to study non perturbative
hadronization mechanisms.Comment: 35 pages, 12 figures, accepted for pubblication in Phys. Rev.
Realistic Model of the Nucleon Spectral Function in Few- and Many- Nucleon Systems
By analysing the high momentum features of the nucleon momentum distribution
in light and complex nuclei, it is argued that the basic two-nucleon
configurations generating the structure of the nucleon Spectral Function at
high values of the nucleon momentum and removal energy, can be properly
described by a factorised ansatz for the nuclear wave function, which leads to
a nucleon Spectral Function in the form of a convolution integral involving the
momentum distributions describing the relative and center-of-mass motion of a
correlated nucleon-nucleon pair embedded in the medium. The Spectral Functions
of and infinite nuclear matter resulting from the convolution formula
and from many-body calculations are compared, and a very good agreement in a
wide range of values of nucleon momentum and removal energy is found.
Applications of the model to the analysis of inclusive and exclusive processes
are presented, illustrating those features of the cross section which are
sensitive to that part of the Spectral Function which is governed by
short-range and tensor nucleon-nucleon correlations.Comment: 40 pages Latex , 16 ps figures available from the above e-mail
address or from [email protected]
Analisis Peranan Algoritma Angka dan Kata dalam Peningkatan Kemampuan Problem-solving Matematika pada Siswa Satap SMPN 6 Kupang Tengah
Pembelajaran matematika pada umumnya tidak terlepas dari perhitungan, penyusunan pola/bentuk dan pemikiran logik matematik. Oleh sebab itu, metode pembelajarannya haruslah asyik dan menyenangkan. Hal ini merupakan tantangan bagi para pendidik pada umumnya dan guru sekolah menengah pertama khususnya agar memotivasi anak didik/siswa-siswinya untuk memiliki beberapa keahlian matematika. Keahlian matematika berupa aritmatika, algoritma angka maupun algoritma kata kata sangat penting saat menyelesaikan soal-soal matematika terlebih soal cerita atau soal yang membutuhkan daya nalar (logika) yang benar. Tujuan dari penelitian ini adalah untuk menyelidiki kesulitan siswa dalam kemampuan aritmatika, algoritma angka dan algoritma kata-kata saat menyelesaikan permasalahan (problem-solving) matematika dan menemukan metode pembelajaran matematika yang dapat membantu siswa SATAP SMPN 6 Kupang Tengah dalam menyelesaikan persoalan matematika berdasarkan atas aspek aritmatika, algoritma angka dan algoritma kata. Hasil penelitian ini menunjukkan bahwa Kemampuan Algoritma kata dalam menyelesaikan persoalan matematika sangat dipengaruhi oleh kemampuan dalam menyelesaikan masalah non verbal (mampu berlogika), kemampuan algoritma angka dan memori jangka panjang (secara langsung maupun tidak langsung) sedangkan aritmatika dan kerja memori berpengaruh secara tidak langsung terhadap kemampuan algoritma kata (menyusun prosedur dalam penyelesaian soal cerita matematika). Dan juga perlu adanya penerapan metode yang menarik yaitu metode tanya jawab supaya mahasiswa lebih aktif dalam mengungkapkan pendapat serta metode permainan matematika yang menggunakan kemampuan berlogika seperti quis-quis (asah otak atau teka-teki) matematika sederhana
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