Deep Inelastic Scattering and its Impact on Quark...
Transcript of Deep Inelastic Scattering and its Impact on Quark...
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Deep Inelastic Scattering and
its Impact on Quark Models
Saptaparnee Chaudhuri
Department of Physics and
Astronomy
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Nobel Prize in Physics in 1990
Jerome I. Friedman Henry W. Kendall Richard E. Taylor
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Scattering can determine structure:
Rutherford’s great legacy
Rn (alpha particle
source)
Alpha particle
Zinc sulphide screen
Microscope
Gold foil
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Atomic Nucleus Discovered in 1911
Protons Discovered in 1919
Neutron Discovered in 1932
In late 1950’s the protons RMS radius was found to be about 10-13
cm.
Are they Fundamental particles? 4
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1964 Gell-Mann & Zweig proposed that protons and
neutrons and other particles are composed of spin ½
constituents- QUARKS
3 types
UP, DOWN, STRANGE
they have fractional charges UP(+2/3) DOWN(-1/3) STRANGE(-1/3)
Proton(u,u,d) Neutron(d,d,u)
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Are Quarks Real?
Many Unsuccessful Searches
-Accelerators, Cosmic Rays, Terrestrial Environment, Sea Water,
Meteorites, Air etc.
Fractional Charges
-Considered by many to be unreasonable
General Point of View In 1966
Quarks are most likely just mathematical representations
Useful but NOT real!
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Stanford Linear Accelerator Completed in 1966
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The SLAC-MIT Experiment
Linear Accelerator (SLAC) provided
20 Billion electron-volt electrons
Effective Magnification was 60 Billion times greater than
ordinary light
(Effective Magnification is proportional to Energy)
Examined the insides of the protons and neutrons
PROVIDED THE FIRST DIRECT
EVIDENCE FOR QUARKS
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SLAC Magnetic Spectrometers
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Picture reference” Rutherford’s legacy in particle physics:Exploring
the proton” 10
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The Experiment(continued)
Deep Inelastic electron-proton scattering
e + p e + Many Particles
Electron
p
p'
Proton
P=(M,0)
Hadrons
P’
q = p-p’
Momentum transfer
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Nuclear Form Factor
f(x) is the charge
function
q = p – p’
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Results suggested that protons has “point-like” constituents
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|F(q2 ) |2
Probing particle
Object
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References. Particles and nuclei by Povh. Rith. Zetsche Rutherford’s legacy in Physics:Exploring the proton