spin is everywhere… why do cats always land on their feet? evidence for dark matter in the...
Post on 15-Dec-2015
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Spin in quantum mechanics……
O. Klein
G. Uhlenbeck
A. Goudsmit
P. Ehrenfest (1925):“This is a good idea.
Your idea may be wrong,but since both of you are
so young without any reputation, you would
not loose anything makinga stupid mistake.”
…. spin as a fundamental property of elementary particles:
Proton spin
• The value: S =
• The original idea:
• The applications:
21
21 quarkp SSp
Example: MRI Alzheimer’s disease
© VUMC Alzheimercentrum
The origin of proton spin
• European Muon Collaboration (EMC) @ CERN (1985):
• ZEUS and H1 experiments @ DESY (early ’90’s):
Quarks carry only a small fraction of the proton spin
In the proton abundantquark-antiquark pairs and gluons are found.
gluon
Quark-antiquark pair
Search the carriers of proton spin
½ = ½ q + G + Lq
• Three possible
sources:
quark-antiquarks
(sea quarks) gluons orbital momentum
• Mathematically:
~ 30% ? ?
(Valence Sea Quarks?)
HERA e-p collider at DESY
The HERMES experiment at HERA:
6.2 km circumference ring,
27 GeV e+ & 920 GeV p’s
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