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Contact Information
Tel : 972-8-9342570
Fax : 972-8-9344106
Rm.: 334
Email: avraham.rinat@weizman.ac.il
Secretariat:
Corinne Hasdai
Tel : 972-8-9343835
Email: corinne.hasdai@weizmann.ac.il
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Avraham Rinat,
Professor Emeritus
Department of Particle Physics
Weizmann Institute,
76100 Rehovot,
Israel
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Current Research Interests
Inclusive scattering on matter.
One of the
universal problems in physics is the description of matter,
composed of many particles, when one has information on the nature of the
force between two constituents. The quest exists in atomic, molecular,
nuclear and astro-physics, and to some extent in
particle physics.
As always there
are two aspects. Can one develop
practical tools to
compute matter properties and devise experiments which test those?
The above topic is one approach to the problem. It is a special case of
projectiles, which are directed towards
a target and where subsequent
analysis should provide information. The
simplest type is elastic
scattering, when the projectile does not loose energy
to the target,
which remains in the state it was before the
scattering. However, the
projectile gets deflected from its original path and from it, one distils
information on the distribution of particles
in matter. Prime examples
are x-ray diffraction from
crystals and the distribution of protons
inside a nucleus.
Occasionally a
projectile does loose energy to the
target. The
probability of occurrence provides specific
information on the structure
of the target.
Inclusive scattering is a particular
kind of inelastic scattering, where
a large amount of energy is transferred
to a target, enabling the
excitation of many modes, without there
existing information for a
selected one. The same holds
for the momentum transferred. In the
experiment one deliberately detects only the
projectile, or a very
limited of other particles. It
turns out that the information is
nevertheless very rich.
Had the projectile hit only one
particle which, due to the large energy
imparted to it, had no opportunity to scatter from others, a
description
of the event must be simple on account of energy-momentum balance in
the
projectile-particle collision. However, a particle in a medium has no
definite momentum. As a result, the
experiment gives basic information
on the probability that a constituent has a given momentum.
The description above assumes that one
knows what the 'constituents' are.
What particles does one see if one
bombards a complex molecule, a
nucleus, or a proton? The answer
lies in the energy involved in the
encounter. When growing, it will be capable
to excite finer details and
disclose ever smaller sub-structures. One may thus bombard a nucleus
with electrons and in an analysis find that the basic
constituents for
the given energy are protons and nucleons, undistinguishable from
point-
particles. Increasing the
energy, one will see that those nucleons have
finite dimensions. Still increasing the energy
discloses that nucleons
are composed of quarks and gluons, etc.
In addition to
the above, one encounters noise in each energy regime: a
hit particle does not leave the target without colliding with others and
those modify the simple picture above. That noise can be turned to
information on how 2,3... constituents behave
in a medium of many, which
is a crucial question in many-body physics.
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