another route to cp violation beyond the sm – particle dipole moments
DESCRIPTION
Another Route to CP Violation Beyond the SM – Particle Dipole Moments. Dave Wark Imperial/RAL. WIN05 Delphi June 10, 2005. WIN05. June 10 ’05. nEDM…. ⇀. Would lead to a non-zero value for d n , either parallel or anti-parallel to s. ⇀. …and CP. Particle Electric Dipole Moment. _. - PowerPoint PPT PresentationTRANSCRIPT
Another Route to CP Violation Beyond the SM –Particle Dipole Moments
Dave WarkImperial/RAL
WIN05 Delphi
June 10, 2005
…and C
P
nED
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WIN05June 10’05 Particle Electric Dipole Moment
+_ s⇀
Would lead to a non-zero value for dn, either parallel or anti-parallel to s⇀
⇀
dn would be:P oddT odd
CP odd!
⇀
Imperial College/RALDave Wark
10-32
10-20
10-22
10-24
10-30
Standard Model10-34
10-36
10-38
Ran
ge o
f d
(e
cm)
in v
ario
us
mod
els
electron
neutron
10-26
10-28
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nED
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WIN05June 10’05
Imperial College/RALDave Wark
Left-Right
10-32
10-20
10-22
10-24
10-30
MultiHiggs SUSY
Standard Model
Electro-magnetic
10-34
10-36
10-38
Ran
ge o
f d
(e
cm)
in v
ario
us
mod
els
neutron
electron
Strong CPV dn ~ 10-16 ecm
…and C
P
nED
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WIN05June 10’05
Imperial College/RALDave Wark
Exp
erim
enta
l Lim
it o
n d
(e
cm)
1960 1970 1980 1990
Left-Right
10-32
10-20
10-22
10-24
10-30
MultiHiggs SUSY
Standard Model
Electro-magnetic
neutron:
electron:
10-34
10-36
10-38
2000
10-20
10-30
Ran
ge o
f d
(e
cm)
in v
ario
us
mod
els
neutron
electron
Relative value of neutronand electron EDM is model-dependent, must pursue both
Strong CPV dn ~ 10-16 ecm
…and C
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WIN05June 10’05
Dave Wark Imperial College/RAL
Exp
erim
enta
l Lim
it o
n d
(e
cm)
1960 1970 1980 1990
Left-Right
10-32
10-20
10-22
10-24
10-30
MultiHiggs SUSY
Standard Model
Electro-magnetic
neutron:
electron:
10-34
10-36
10-38
2000
10-20
10-30
Ran
ge o
f d
(e
cm)
in v
ario
us
mod
els
neutron
electron
Cited >200 times already
Strong CPV dn ~ 10-16 ecm
…and C
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nED
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WIN05June 10’05
Imperial College/RALDave Wark
If neutron were the size of the earth...
x
-e
+e
... current EDM limit would correspond to charge separation of x 10 .
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WIN05June 10’05
Imperial College/RALDave Wark
B dn ??
B E
Basic Idea of the Measurement
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WIN05June 10’05
Imperial College/RALDave Wark
B dn ??
B E
Basic Idea of the Measurement
Look for a shift in the Larmor frequency of 2·E·dn as E is flipped
relative to B
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WIN05June 10’05
Imperial College/RALDave Wark
4.
3.
2.
1.
Free precession...
Apply /2 spinflip pulse...
“Spin up” neutron...
Second /2 spinflip pulse.
The RamseySeparatedOscillatorMethod
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WIN05June 10’05
Imperial College/RALDave Wark
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Imperial College/RALDave Wark
>> interatomic spacing; neutrons see Fermi potential VF
Critical velocity for reflection:
½mvc2 = VF
Ultracold neutrons (UCN): v 6 m/s: total internal reflection possible.
vc depends on orientation of neutron spin, so can
polarise by transmission.
n
n
ns
s
B
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WIN05June 10’05
Imperial College/RALDave Wark
( )dET Nn
2
dN N N N
ETNn ( )
1 2 1 2
2
Prepare neutrons in polarisation state 1, execute Ramsey cycle and measure the number left in states 1 and 2, repeat with B and E fields parallel () and anti-parallel (), then:
With the resulting “statistical” sensitivity:
Must add any systematics to this to determine the sensitivity of the experiment. …and C
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nED
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WIN05June 10’05
Imperial College/RALDave Wark
The Institute Laue-Langevin
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WIN05June 10’05
Dave Wark Imperial College/RAL
N S
Four-layer mu-metal shield High voltage lead
Quartz insulating cylinder
Coil for 10 mG magnetic field
Upper electrodeMain storage cell
Hg u.v. lamp
PMT to detect Hg u.v. lightVacuum wall
Mercury prepolarising
cell
Hg u.v. lampRF coil to flip spins
Magnet
UCN polarising foil
UCN guide changeover
Ultracold neutrons
(UCN)
UCN detector
Current Room-Temperature
nEDMExperiment
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WIN05June 10’05
Dave Wark Imperial College/RAL
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WIN05June 10’05
Dave Wark Imperial College/RAL
1999 Results (PG Harris et al, PRL 82, 904 (1999))
dn = (1.9 5.4)1026 e cm
dn 6.3 1026 e cm (90% c.l.)
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WIN05June 10’05
Dave Wark Imperial College/RAL
PublishedData
CurrentRoom-Temp
CryogenicExperiment
NET2)d( n
Recall:
α
E
T
N
0.5
4.5 kV/cm
130 s
13000
0.7
12 kV/cm
130 s
14000 …and C
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WIN05June 10’05
Dave Wark Imperial College/RAL
How will we do better?• Need a new source of UCN….
• To use this we need….
1.03 meV
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WIN05June 10’05
Dave Wark Imperial College/RAL
Next Generation Experiment
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WIN05June 10’05
Dave Wark Imperial College/RAL
Ramsey Cell and SF Vessel
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WIN05June 10’05
Dave Wark Imperial College/RAL
PublishedData
CurrentRoom-Temp
CryogenicExperiment
NET2)d( n
Recall:
α
E
T
N
0.5
4.5 kV/cm
130 s
13000
0.7
12 kV/cm
130 s
14000
0.9
40 kV/cm
300 s
700000 …and C
P
nED
M…
WIN05June 10’05
Dave Wark Imperial College/RAL
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Dave Wark Imperial College/RAL
199Hg Electric Dipole Momenthep-ex/0012001
• Optically pumped 199Hg atoms precess in B, E fields, modulating absorption signal
Dual cells remove effect of drifts in B
Result: d(199Hg) < 2.1 x 10-28 e cm
Provides good limit on CPv effects in nuclear forces, inc. QCD
If from valence neutron, corresponds to dn<2x10-25 ecm, because of electrostatic shielding.
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WIN05June 10’05
Dave Wark Imperial College/RAL
Slid
e fr
om E
d H
inds
Slid
e fr
om E
d H
inds
Slid
e fr
om E
d H
inds
Slid
e fr
om E
d H
inds
Slid
e fr
om E
d H
inds
Slid
e fr
om E
d H
inds
Conclusions• Particle EDMs are sensitive probes of CP
violation both within (s < 2-6 x 10-10) and in models beyond the SM (The natural scale for the nEDM is SUSY is 10-23, already stressed).
• Experiments are in progress to improve sensitivities by factors 100-1000.
• There are other competing experiments for both neutrons (PSI, US) and electrons that I have no time to discuss.
• There are also plans to push limits on the muon EDM at future facilities (JPARC).
• The two CP violation communities seem completely separate, which is a pity….
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WIN05June 10’05
Dave Wark Imperial College/RAL