Eric Prebys, FNAL
Summarizing steering committee working group, chaired by W.
Molzon and A. de Gouvea
3/28/2008E. Prebys - PAC Presentation
Two classes of muon experiments have been identified as particularly promising for an intensity-based program e conversion
A dramatic improvement in the search charged lepton flavor violation (CLFV)
Broadly sensitive to new physics Complementary to proposed e searches (eg, MEG) Can exploit voluminous work done for MECO proposal at BNL
Anomalous muon magnetic moment (g-2) Already shows hint of possible new physics Can transport apparatus from previous experiment at
Brookhaven Significant improvements in experimental technique and
theoretical uncertainty
23/28/2008E. Prebys - PAC Presentation
Forbidden in Standard Model Observation of neutrino mixing shows this can occur at a very small rate
Photon can be real (->e) or virtual (N->eN)
3
e
0Z
First Order FCNC: Higher order dipole “penguin”:
e
Virtual mixing
W
54
2
3,22
21* 10
32
3)(
i W
ieii M
mUUeBr
3/28/2008E. Prebys - PAC Presentation
3/28/20084
Courtesy: A. de Gouvea
?
?
?
Sindrum IIMEGA
MEG proposal
We can parameterize the relative strength of the dipole and four fermi interactions.
This is useful for comparing relative rates for NeN and e
E. Prebys - PAC Presentation
1
10-2
10-16
10-6
10-8
10-10
10-14
10-12
1940 1950 1960 1970 1980 1990 2000 2010
Initial mu2e Goal
- N e-N
+ e+ + e+ e+ e-
K0 +e-
K+ + +e-
SINDRUM II
Initial MEG Goal
10-4
10-16
3/28/2008 5E. Prebys - PAC Presentation
3/28/2008
Rate limited by need to veto prompt backgrounds!
12103.4capture
Ti
TieTiR e
High energy tail of coherent Decay-in-orbit (DIO)
E. Prebys - PAC Presentation
3/28/20087
Eliminate prompt beam backgrounds by using a primary beam with short proton pulses with separation on the order of a muon life time
Design a transport channel to optimize the transport of right-sign, low momentum muons from the production target to the muon capture target.
Design a detector to strongly suppress electrons from ordinary muon decays
~100 ns ~1.5 s
Prompt backgrounds
live window
E. Prebys - PAC Presentation
8
MECO spectrometer design
for every incident proton 0.0025 ’s are stopped in the 17 0.2 mm Al target
foils
3/28/2008E. Prebys - PAC Presentation
3/28/20089
Deliver beam to Accumulator/Debuncher enclosure with minimal beam line modifications and no civil construction.
Recycler(Main Injector
Tunnel)
MI-8 -> Recycler done for NOvA
New switch magnet extraction to P150 (no need for kicker)
E. Prebys - PAC Presentation
3/28/200810
Exploit NOvA accelerator modifications and post-Run II availability of Accumulator and Debuncher rings to mount a ->e conversion experiment patterned after MECO 4x1020 protons in ~2 years Measure
Single event sensitivity of Re=2x10-17
90% C.L. limit of Re<6x10-17
Improvement over existing limit of more than four orders of magnitude (one order of magnitude in effective mass reach)
ANY signal = Beyond Standard Model physics
capture Al
AlAl
e
R e
E. Prebys - PAC Presentation
Example Sensitivities*
CΛ = 3000 TeV
-4HH μμμeg =10 ×g
Compositeness
Second Higgs doublet
2Z
-17
M = 3000 TeV/c
B(Z μe) <10
Heavy Z’, Anomalous Z
coupling
Predictions at 10-15
Supersymmetry
2* -13μN eNU U = 8×10
Heavy Neutrinos
L
2μd ed
M =
3000 λ λ TeV/c
Leptoquarks
*After W. Marciano
3/28/2008 11E. Prebys - PAC Presentation
3/28/200812
The Project X linac would provide roughly a factor of ten increase in flux. Or could allow this experiment to run concurrently with
other experiments requiring similar intensity Investigating scheme for proton delivery Direct extraction from Recycler? Injection into Accumulator, then manipulate as before?
Also investigating improvements to muon transport efficiency based on muon collider/neutrino factory R&D
The combination of increased flux and efficiency could potentially push the 90% C.L. sensitivity to ~10-18
E. Prebys - PAC Presentation
13
1992 MELC proposed at Moscow Meson Factory
1997MECO proposed for the AGS at Brookhaven as part of RSVP (at this time, experiment incompatible with Fermilab)
1998-2005intensive work on MECO technical design: magnet system costed at $58M, detector at $27M
July 2005 RSVP cancelled for financial reasons
2006MECO subgroup + Fermilab physicists work out means to mount experiment at Fermilab
June 2007 mu2e EOI submitted to Fermilab
October 2007 LOI submitted to Fermilab
Fall 2008 mu2e submits proposal to Fermilab
2010 technical design approval: start of construction
2014 first beam
To lowest order, the muon magnetic moment (g) is 2 g is perturbed by contributions from virtual loops, from both
the Standard Model and (possibly) beyond. The calculation and measurement of the “anomalous
magnetic moment”
stands as one of the most precise tests of the Standard Model
14
2
2g
3/28/2008E. Prebys - PAC Presentation
B
QED
Z
Weak Had LbL
Had VP
Had VP
muons
hadrons
ee
eesR
m
,had sRssK
dsa2
1
KEY REGION
2006 plot
3/28/2008 15E. Prebys - PAC Presentation
R-parity conserving Supersymmetry (vertices have pairs)
And the diagrams are amplified by powers of tan (here linearly)
3/28/2008 16E. Prebys - PAC Presentation
is determined from the ratio of the muon precession frequency (a) and the magnetic field (B).
17
Momentum
Spin
e
a
3/28/2008E. Prebys - PAC Presentation
18
K. Hagiwara, A.D. Martin, Daisuke Nomura, T. Teubner
Compare
TIME
Rep.Prog.Phys. 70, 795 (2007).
)4.3( 10)88295()theor.()expt.(
ppm) 48.0(10)6.5.(11658180)theor.(
ppm) 54.0(10)3.6.(11659208)expt.(
11
10
10
Theory+exp. input
3/28/2008E. Prebys - PAC Presentation
Increase muon flux with better beam optics
Decrease contamination with long transport channel
Improve injection kicker to increase number of stores
193/28/2008E. Prebys - PAC Presentation
Ankenbrandt and Popovic, Fermilab
g-2
Test Facility
Booster-era Beam Transfer Scheme
Rare Kaon Decays
Alternative ?
3/28/2008 20E. Prebys - PAC Presentation
Event Method
Geant simulation using new detector schemes
Energy Method
Same GEANT simulation
3/28/2008 21E. Prebys - PAC Presentation
22
Phase 1: + measurement to 0.1 ppm statistical Requires Nova type upgrades, beam manipulations and
~4x1020 p Can do in pre Project X era
Phase 2: - measurement to 0.1 ppm (or lower) Requires many more protons due to xsection for -
Would benefit from Project X
Phase 3: All “integrating” with much higher proton beam and restricted storage ring acceptance to lower systematics
Requires Project X
3/28/2008E. Prebys - PAC Presentation
E. Prebys - PAC Presentation
σsystematic 1999 2000 2001 Future
Pile-up 0.13 0.13 0.08 0.04
AGS Background 0.10 0.10 0.015*
Lost Muons 0.10 0.10 0.09 0.04
Timing Shifts 0.10 0.02 0.02
E-Field, Pitch 0.08 0.03 0.06* 0.05
Fitting/Binning 0.07 0.06 0.06*
CBO 0.05 0.21 0.07 0.04
Beam Debunching 0.04 0.04 0.04*
Gain Change 0.02 0.13 0.13 0.03
total 0.3 0.31 0.21 ~0.09
3/28/2008 23
E. Prebys - PAC Presentation
Future
3/28/2008 24
E. Prebys - PAC Presentation
This CMSSM calculation: Ellis, Olive, Santoso, Spanos. Plot update: K. Olive
gaugino mass
scal
ar m
ass
Excluded for neutral dark matter
1
2
With new experimental and theoretical precision and same a
Present:a = 295 ± 88 x 10-11
Futurea = 295 ± 39 x 10-11
Topical Review: D. Stöckinger hep-ph/0609168v1
Here, neutralino accounts for the WMAP
implied dark matter density
3/28/2008 25
Precision muon measurements offer powerful tools for the investigation of physics beyond the Standard Model.
Both the e conversion experiment and the g-2 measurement fit well into an intensity-based program at Fermilab.
These programs have the potential for a staged approach, beginning in the NOvA era and expanding in the Project X era.
3/28/2008E. Prebys - PAC Presentation 26
273/28/2008E. Prebys - PAC Presentation
January 31 2008William Molzon, UC Irvine Muon
Physics at Fermilab 28
MEG experiment (running) at Paul Scherrer Institute: →eto ~10-13
Difficult to improve beyond that (perhaps to 10-14) due to accidental backgrounds
Reprise of MECO/mu2e at BNL Fermilab has better time structure, duty cycle, running time per year, higher
intensity COMET at JPARCMuon beam flux, time structure similar to MECO design sensitivity below 10-16
Detectors displaced from stopping target to reduce rates PRISM/PRIME at JPARCVery different muon beam: FFAG storage ring for
phase rotation, very intense pulses at low frequency (<1kHz)
Very small, narrow momentum spread beam, thintarget, detector arrangement similar to COMET
Would require new building, technical advances Prime disadvantage of both COMET and PRISM/PRIME is conflict with running neutrino beam
29
Examples with >>1 (no e signal):LeptoquarksZ-primeCompositenessHeavy neutrino
SU(5) GUT Supersymmetry: << 1
Littlest Higgs: 1
Br(e)
Randall-Sundrum: 1
MEG
mu2e
10-12
10-14
10-16
10-1110-1310-15
R(TieTi)
10-13 10-11 10-9
Br(e)
10-16
10-10
10-14
10-12
10-10
R(TieTi)
3/28/2008E. Prebys - PAC Presentation
http://www.ippp.dur.ac.uk/~georg/sps/sps.html
10-11 units
29331816.513549086169237173-90
Compare to present a =295 ± 88
Next stage to a < ±39
Snowmass Points and Slopes: