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P4紹介文 - (2007/12/25 (火) 23:31:22) のソース

<p> introduction</p>
<p>　As well known, a nucleus consists of protons and neutrons (i.e.
nuclei).<br>
In general, the number of each nuclei don't give us other information about
that.<br>
For example, because we know not all about strong interaction which is
attraction force between nucleons, we can't construct the theory of verifying
existence of nuclear and their shapes by considering interaction between
nucleon.<br>
In detail, analysis is difficult by the fact that nuclear is few-many-body
systems, that is, the number of particle constructing nuclear is from several
number to the order of 100.<br>
In other words, if we understand all about that interaction, it is difficult to
analyze because the number of constructing particles is too much large as
analysis and  too much small as considering statistically.<br>
　This is why, although it have passed about one century from discovered,
research is acted by using the most advanced devise.<br>
　Furthermore, in resent days, particle accelerator is developed, and some
people try to explain the nature of interaction between nuclei or the structure
within nuclear by generating and studying unnatural particle e.g. neutron rich
nuclei or unstable nuclei.<br>
　In theoretical physics, it is often used that QCD is applied to quark model
for the purpose of showing the nature of nuclear.</p>
<p><br>
 our research</p>
<p>　In this year, we study the way of measuring the shape of certainty nuclear
by follow experiment.<br>
　Because nuclear consists of proton and neutron, it is efficient to research
the density distribution of proton and neutron when we try to measure the shape
of nuclear<br>
About proton's distribution, it is measured by using the method of electron
scattering because of it's electromagnetic interaction.<br>
　But, measuring neutron's one is much more difficult as proton's one.<br>
This is because that is complement only when using interaction between
nucleons, for example proton scattering.<br>
　However, to our joy, it is known by ever experiment that proton's in nuclear
is approximately equal to neutron's one.</p>
<p>　It is particularly shown that, in nuclear having large mass, density is
distributed as following Fermi-Dirac static in finite temperature.<br>
　In our experiment, by the use of these facts, we think to try to measure those
densities and to determine the shape of nuclear.<br>
　Different from neutron rich nuclei, on which neutron's density distribution is
broader by proton's one, nuclear used in our experiment is stable.<br>
　To be concretely, we apply electron beam to target (nuclei) at first and
measure the number of scattered electron with respect to the angles to the beam
line, and then calculate the differential cross section and 'form factor',
which is needed in determining the shape of nuclei.<br>
　We do experiment in institute for chemical research in Kyoto University and
utilize electron beam which energy is 100MeV, so the movement of electron must
be deled relatively.<br>
So, when we calculate the differential cross section, we use not the Rutherford
scattering formula but the Mott scattering formula.<br>
　The Mott scattering formula is intended for point charge, so considering the
finite extent of nuclear, we have to multiply 'form factor' to the differential
cross section.<br>
　'Form factor' signifies the shape of nuclear, and this is derived by
three-dimensional Fourier transform of density distribution of proton.<br>
　So,　for calculating the density distribution of proton, we have to decide
model of some density distribution, and have to fit it into 'form factor' after
giving it Fourier transform.<br>
It becomes problem what kind of model we use in fitting.<br>
To use the Fermi function is easiest, but we want to fit more exactly.<br>
That distribution,　i.e. probability of existence,　is decided when we derive the
wave function from potential included in Schrodinger equation.<br>
　So, in this situation, most important thing is how we determine the potential
which a particle has.<br>
It is simplest to do numerical calculation by applying simple potential, for
example, Wood-Saxon potential.<br>
However, we don't use such potential.<br>
We will try to think one model as not contradictory to the idea that nuclear is
consisted of many composition, and to make potential based on that model.<br>
In addition to this, we think it is better to make potential for
self-consistent by the use of Hartree-Fock approximation.</p>
<p> about our experiment<br>
In this section,　information about our experiment is written.<br>
At first,　we accelerate electron beam to 100MeV by LINAC.<br>
In the next, that beam is collided to target, and we detect scattered one by
plastic scintillator and PM.<br>
In fact, nuclear is excited, so it is occurred not only elastic scattering but
also non-elastic scattering.<br>
Therefore, we bend the scattered electron by magnet, and distinguish elastic
scattering electron from another by the use of bending angle dependent on
momentum.<br>
In this process, resolution of measured momentum is about 2MeV.<br>
So, when we use the target which nuclear excited state have lower energy than
2MeV,　that distinct is impossible.<br>
As considering this conclusion, we decide to study the shape of C,Pb,Ca,and
O.<br>
A little thinking practically enables us to notice that Ca has hydroscopy and
that O is gas in room temperature.<br>
So, both simple substance isn't suitable for target.<br>
Consequentry, we will use C, Pb, CaO, and H2O as target.<br>
In addition, natural Pb contains comparatively much isotope and isn't suitable
too,　so we get pure Pb and use it for target.</p>
<p><br>
 textbook</p>
<p>教科書<br>
　実験<br>
Leo</p>
<p> </p>
<p>　理論<br>
前期：Shapes and Shells in Nuclear Structure<br>
Sven Goesta Nilsson and Ingemar Ragnarsson, Cambridge university press<br>
　　　　　原子核の理論について概説したもの。原子核を、微視的にquarkなど素粒子の相互作用からアプローチするのではなく、多体系として捉えて現象論的なモデル（liquid
drop model）やshell modelなどから原子核の構造にアプローチするという手法をとっている。</p>
<p><br>
Book used in 1st semester<br>
Title:Shapes and Shells in Nuclear Structure<br>
Author:Sven Goesta Nilsson and Ingemar Ragnarsson, Cambridge university
press<br>
Abstruct:A variety of models can be used to study nuclear structure and
dynamics. This book gives a comprehensive overview of these various models,
concentrating in particular on a description of deformed, and rotating, nuclei.
Following a treatment of the semi-empirical mass formula and nuclear stability,
the liquid-drop and simple shell models are introduced and described. The
spherical nuclear one-particle potential is introduced and developed to cover
the case of deformed nuclei. The latter chapters of the book are devoted to
discussions of barrier penetration, fast nuclear rotation, nucleon-nucleon
interactions, and the pairing interaction. Many problems and solutions are
included that help to illustrate key concepts. The book will be invaluable to
graduate students of nuclear physics, and to anyone engaged in research in this
field.</p>
<p>　　　後期：Computational Physics<br>
　　　　　　　Koonin<br>
　　　　　原子核理論には数値計算が必須であるため、数値計算の手法とその物理への応用を念頭に置いて書かれた本。数値スキームよりは数値計算の物理への応用に重点を置いた本であり、様々な物理現象の例が挙げられている。</p>
<p>Book used in 2nd semester<br>
Title:Computational Physics<br>
Author:Koonin</p>
<p> </p>
<p> </p>
<p> </p>
<p><br>
つまり in other words ,that is to say,in short,namely, i.e.<br>
従って therefore,consequently<br>
さらに moreover,futhermore</p>