A new method of measuring the muon g2

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A new method of measuring the muon g-2

• Francis J.M. FarleyTrinity College Dublin

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There is more than one way to kill
a cat
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Four ways to measure the muon anomalous moment
(g-2)/2
Three have been shown to work
Fourth not yet tried ...... might be best of all
Tests a fundamental prediction of the standard
model
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Henry, Shrank Swanson 1969
Below theory .... but if one applies pitch
correction it is close
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No pulse magnets .... muons make 1600 turns and
emerge spontaneously at the other end
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Charpak, Farley, Nicolai, Sens, Zichichi, York,
Garwin
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started g-2 at CERN
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CERN muon storage ring
Bailey et al. 1968, 1972
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14m diameter muon storage ring at CERN

g-2 frequency is same at all radii
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Muon storage rings
t
CERN 1.2 GeV gradient field, weak
focusing
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proton injection
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Sulak
Debevec, Farley, Hertzog, Roberts, Bunce,
Krienen, Morse, Hughes,
Jungmann, Semertzidis
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Blind analysis ... magnetic field
evaluated by one group g-2 frequency
evaluated by another group take
ratio to calculate
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Comparison with theory
from Hoecker hep-ph/0410081 v2
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The future
OR
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AG muon storage ring
Increase energy to 15 GeV
5 x more g-2 cycles to measure
? increase B to 3 - 4 T ?
10 x more cycles to measure
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Ring design
Courant Snyder, Annals of Physics (1958)
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Q vs open wedge angle for 4 sector ring
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3 sector concept
need 10 billion recorded decay electrons
say 50 billion injected muons
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Advantages
no electric quadrupoles
no inflector to cancel the field in the magnet at
injection
simple kicker using ferrite
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A new ring structure for muon g-2 measurements
Nuclear Instruments and Methods, A 523 (2004) 251
Francis J. M. Farley
hep-ex/0307024
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Reduce error in a to 50 ppb ........... ! ! !
µ
Is it worth it ??
uncertainty in theory is 500 ppb
...... but it will improve
Historically experiment has often been ahead of
theory
fine structure
Zeeman effect
Stern Gerlach
Kusch Foley
Lamb shift
Let's give the theorists need something to think
about
In fact they have something to think about already
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HAPPY BIRTHDAY LARRY
Bonne continuation