Transcript Slide 1

WG4 Summary and Future Plans
The muon trio
and
more
B. Lee Roberts
Department of Physics
Boston University
[email protected]
WG4:
m physics
http://physics.bu.edu/roberts.html
B. Lee Roberts, on behalf of the Intense Muon Physics Working Group
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The Muon Trio:
• Lepton Flavor Violation
• Muon MDM (g-2)
chiral changing
• Muon EDM
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MEG
MECO
PRIME
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Today with e+e- based theory:
All E821
results were
obtained
with a “blind”
analysis.
world average
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Electric and Magnetic Dipole Moments
Transformation properties:
An EDM implies both P and T are violated. An EDM at
a measureable level would imply non-standard model
CP. The baryon/antibaryon asymmetry in the universe,
needs new sources of CP.
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Present EDM Limits
Particle
Present EDM limit
SM value
(e-cm)
(e-cm)
n
future
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m exp
m physics
10-24 to 10-25
*projected
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General Statements
• We know that n oscillate
– neutral lepton flavor violation
• Expect Charged lepton flavor violation
at some level
– enhanced if there is new dynamics at the
TeV scale
• in particular if there is SUSY
• We expect CP in the lepton sector
(EDMs as well as n oscillations)
– possible connection with cosmology
(leptogenesis)
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The Physics Case:
• Scenario 1
– LHC finds SUSY
– MEG sees m → e g
• The trio will have SUSY enhancements
– to understand the nature of the SUSY
space we need to get all the information
possible to understand the nature of this
new theory
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SUSY predictions of m-A  e-A
10 -11
m 0
m 0
From
Barbieri,
Hall,
Hisano …
10 -13
Rme
10 -15
10 -17
10 -19
MECO single event
sensitivity
PRIME single event
sensitivity
10 -21
100
200
300 100
200
m  eg & m-A  e-A Branching
Ratios are linearly correlated
Complementary measurements
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300
BR m  eg 
BR mA  eA 
m e (G e V )
R
 200  300
(discrimination between SUSY models)
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Connection with n oscillations
Additional contribution to slepton mixing from V21, matrix element responsible
for solar neutrino deficit. (J. Hisano & N. Nomura, Phys. Rev. D59 (1999) 116005).
tan(b) = 30
Largely favoured
and confirmed by Kamland
tan(b) = 0
Experimental
bound
MEG goal
After
Kamland
All solar n experiments combined
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SUSY connection between am , Dμ , μ → e
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aμ sensitivity to SUSY (large tanb)
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SUSY, dark matter, (g-2) DE821
CMSSM
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D E969 = Dnow
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D E969 = 0
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The Physics Case
• Scenario 2
– LHC finds Standard Model Higgs at a
reasonable mass, nothing else, (g-2)
discrepancy could be the only indication
beyond neutrino mass of New Physics
• Then precision measurements come to
the forefront, since they are sensitive
to heavier virtual particles.
– μ-e conversion is especially sensitive to
other new physics besides SUSY
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Sensitivity to Various me Conversion Mechanisms
Supersymmetry
Compositeness
Predictions at 10-15
Λ C = 3000 TeV
Second Higgs
doublet
Heavy Neutrinos
2
*
U μ NU e N
= 8 × 10
-1 3
g H μe = 10 -4 × g H μμ
Heavy Z’,
Anomalous Z
coupling
Leptoquarks
ML =
3 0 0 0 λ μ d λ e d T e V /c
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M Z  = 3 0 0 0 T e V /c
2
After W. Marciano
B (Z  μ e ) < 1 0
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2
-1 7
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The Experiments: LFV
• μe conversion and Muonium-anti-Muonium
conversion
– pulsed beam
• μ→ eg and eee
– DC beam
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Near Term Experiments on LFV
• MEG @ PSI (under construction, data
begins in 2006)
– 10-13 BR sensitivity
• MECO @BNL (funding not certain)
– 10-17 BR sensitivity
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MEG @ PSI (10-13 BR sensitivity)
Discovery Potential:
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4 Events
BR = 2 X 10-13
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The MECO Apparatus
Straw Tracker
Muon Stopping
Target
Muon Beam
Stop
Superconducting
Transport Solenoid
(2.5 T – 2.1 T)
Crystal
Calorimeter
Superconducting
Production Solenoid
(5.0 T – 2.5 T)
Superconducting
Detector Solenoid
(2.0 T – 1.0 T)
Collimators
p beam
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approved but not funded
10-17 BR single
event sensitivity
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Future Experiments on LFV
• PRIME-type experiment
– with FFAG muon storage ring
– few X 10-19
• Such an experiment is perfect for the
front end of a muon factory
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m + e- → m - e+
Full M search
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Muonium production
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An improvement of 102 on GMM
would confront these types of models
which would also contribute to double
b – decay. At the front end of a n
factory with a pulsed beam this might
be possible.
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Future Muon (g-2) Experiments
• E969 @ BNL 0.5 → 0.20 ppm (scientific
approval but not funded)
– expected near-term improvement in theory,
→ the ability to confront the SM by ~ x 2
• The next generation 0.20 → 0.06 ppm
– substantial R&D would be necessary
• new ring or improved present ring?
WG4:
m physics
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Use an E field for vertical focusing
0
spin difference frequency = ws - wc
WG4:
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Muon (g-2): Store m ± in a storage ring
magnetic field averaged
over azumuth in the
storage ring
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E969: Systematic Error Goal
Systematic uncertainty (ppm) 1998 1999 2000 2001 E969
Goal
Magnetic field – wp
0.5
0.4
0.24
0.17
0.1
Anomalous precession – wa
0.8
0.3
0.3
0.21
0.1
• Field improvements will involve better trolley calibrations,
better tracking of the field with time, temperature stability
of room, improvements in the hardware
• Precession improvements will involve new scraping scheme,
lower thresholds, more complete digitization periods, better
energy calibration
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SM value dominated by hadronic issues:
• Lowest order hadronic contribution ( ~ 60 ppm)
• Hadronic light-by-light contribution ( ~ 1 ppm)
The error on these two contributions will ultimately limit the interpretation
of a more precise muon (g-2) measurement.
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A (g-2) experiment to ~0.06 ppm?
• Makes sense if the theory can be
improved to 0.1 ppm, which is hard, but
maybe not impossible.
• With the present storage ring, we
already have
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Where we came from:
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Today with e+e- based theory:
All E821
results were
obtained
with a “blind”
analysis.
world average
WG4:
m physics
B. Lee Roberts, on behalf of the Intense Muon Physics Working Group
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Muon EDM
• Present limit ~10-19 e-cm
• Could reach 10-24 to 10-25 at a high
intensity muon source?
WG4:
m physics
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Spin Precession Frequencies: m in B field
with both an MDM and EDM
The motional E - field, β
X B, is much stronger
than laboratory electric
fields .
~GV/m with no sparks!
The EDM causes the
spin to precess out
of plane.
WG4:
m physics
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EDM – up/down Asymmetry
• avoid the magic γ and use a radial E-field
to turn off (g-2) precession
• Place detectors above and below the
vacuum chamber and look for an up/down
asymmetry which builds up with time
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Up/Down asymmetry vs. time
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time
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The EDM ring
• run with both μ+ and μ-.
• there must be regions of combined E+B along
with separate focusing elements.
• There needs to be a scheme to inject CW and
CCW.
Possible Muon EDM Ring Parameters
E
2
MV/m
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B
p
0.25T 0.5
GeV/c
g
gt
R
5
11μs
7m
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A possible lattice
Yuri Orlov
WG4:
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NP2
• the figure of merit is Nμ times the
polarization.
• we need
to reach the 10-24 e-cm level.
Narrow pulsed beam every ~100 ms
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Additional topics:
•
•
•
•
•
WG4:
Muons for condensed matter (m SR)
Muon catalyzed fusion (m CF)
Muon lifetime (GF)
Muon capture (gp)
...
m physics
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Depth dependent mSR measurements in near surface regions
Muon Spin Polarisation
1.0
B(z)
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
Superconductor
0
1
2
3
4
5
6
7
8
9
10
7
8
9
10
7
8
9
10
7
8
9
Time (ms)
Muon Spin Polarisation
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
0
1
2
3
4
5
6
Time (ms)
Muon Spin Polarisation
1.0
l
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
z
0
1
2
3
4
6
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
 Magnetic field profile B(z) over nm scale
 B(z)
WG4:
physics lengths of the sc l, x
 Characteristic
B. Lee Roberts, on behalf of the Intense Muon Physics Working Group
m
5
Time (ms)
Muon Spin Polarisation
0
-1.0
-0.6
-0.8
-1.0
0
1
2
3
4
5
6
Time (ms)
10
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Magnetic Field Profile in YBa2Cu3O7-d
YBa2Cu3O7-d, T=20K, Tc=87.5K
hext = 91.5(3) G,
x0 = 1.5 nm fixed, l0 = 137(10) nm
0.01
 Direct, absolute measurement of
magnetic penetration depth
B (T)
l(T ) 
*
ns (T )
effective mass
density of
supercarriers
 Direct test of theories (London, BCS)
hext exp(-z/l(T))
3.4 keV
8.9 keV
15.9 keV
20.9 keV
29.4 keV
1E-3
0
50
100
150
z (nm)
local response 
exponential profile
T.J. Jackson, T.M. Riseman, E.M. Forgan, H. Glückler, T. Prokscha,
E. Morenzoni, M. Pleines, Ch. Niedermayer, G. Schatz, H. Luetkens,
and J. Litterst, Phys. Rev. Lett. 84, 4958 (2000).
m physics
-
 B(z ) = B 0e
l a b (T ) [n m ]
k0  90
WG4:
m
z
l ab ( T )
700
600
T hin F ilm (M eissn er state)
T hin F ilm (m ixed state)
Sing le crystal (m ix ed state,
So nier et a l., P R L 72 (199 4) 744 )
500
400
300
200
100
0
10
20
30
40
50
B. Lee Roberts, on behalf of the Intense Muon Physics Working Group
60
70
80
90
Te m p e ra tu re [K ]
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Beams needed:
• Pulsed intense muon beams
– energy from surface (28 MeV/c) to 3.1
Gev/c
• A few experiments could used DC beam,
but almost all can use the pulse
structure of a pulse, and some ms with
no beam
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Beam requirements: A few examples
Exp.
#m
m→e
1020
(g-2)
1015 <20 ns 1 ms
p
Toff
pulse
width
<20 ns 1–100 ms
pm
Dpm/pm Pol
≤28 Mev/c 3%
N
3.1 Gev/c
Y
mEDM 1018 <20 ns 100-500 ms 0.3-1.5
0.5%
~0.1% Y
Gev/c
WG4:
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Plans for next year
• LFV experiments will continue to develop
the techniques needed for these
challenging experiments
• Muon EDM collaboration will continue to
investigate the appropriate ring
structure.
• Participate in scoping study for n factory
– At present muon physics is not mentioned in
the document of 10 June 2005
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Summary
• The questions addressed are at the center of
the field of particle physics
• There is an important program of muon
physics which will be possible at the frontend of a n factory.
– It makes use of the very intense flux which will be
available there
• If such a muon facility exists, there will also
be a program of other very interesting muon
experiments which is possible.
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m physics
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