the new muon g-2 (and edm) experiment at fermilab david hertzog university of washington psi2010:...
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The New Muon g-2 (and EDM) Experiment at Fermilab
David HertzogUniversity of Washington
PSI2010: Physics of Fundamental Symmetries and Interactions
Why mount a new experiment? Especially in “the LHC era?”
What makes it different compared to BNL E821? Status
a = (g – 2)/2 is non-zero because of virtual loops, which can be calculated very precisely
B
QED
Z
Weak Had LbL
Had VP
Had VP
Known well Theoretical work ongoing
The “g-2 test”: Compare experiment to theory. Is SM complete?
TheoryExptNewPhysics aaa .
Historical Evolution
CERN I
CERN II
CERN III
BNLGOAL
3
2
1
HVP is determined from data
A world-wide effort exists to measure over full range
HVP evaluations by 2 groups, updated Tau’10
Hagiwara, Liao, Martin, Nomura, Teubner (HLMNT)
M. Davier, A. Hoecker, B. Malaescu, Z. Zhang (DHMZ) (BaBar team with access to preliminary data)
a exp – a
SM = (296 ± 81) 10 –11
3.6
Biggest difference is from high multiplicity states now measured at BaBar; > 1 GeV region Reduces cross sections
a exp – a
SM = (259 ± 81) 10 –11 3.2
The new HVP evaluations also affect QED running … and enter the global electroweak fits …
Big shift !
Hadronic Light by Light Scattering Models converging … Noteworthy: PdRV*
Other theory newer efforts Lattice – T. Blum et al (outlines a plan for real calc) Dyson-Schwinger – C. Fischer et al (very controversial) AdS/QCD – Deog-Ki Hong et al – confirm leading ps term
Data connection KLOE-2 small angle tagger and and to measure
off-shell form factors … and compare to models
*Prades, de Rafael, Vainshtein arXiv:0901.0306v1
a(HLbL)tot = 105 ± 26 x 10-11
Theory uncertainty = 51 x 10-11 (0.44 ppm)
Experimental uncertainty = 63 x 10-11 (0.54 ppm)• 0.46 ppm statistical limit was counts• 0.21 ppm precession systematic• 0.17 ppm field systematic
The values & the new experimental goal
Leads to a(Expt – Thy) = 297 ± 81 x 10-11 3.6
11
11
116 592 089 63 10
116 59 793 51 10
Expt
Thy
a
a
1
BN
L E
821
Experimental goal: 63 16 x 10-11
Theory uncertainty expect: 51 30 x 10-11
Leads to a(Expt – Thy) = XXX ± 34 x 10-11
If central value remained, a would exceed 8
Precise knowledge of a will aid in discrimination between a wide variety of standard model extensions
UED models (1D) typically predict “tiny” effects Incompatible with a a of ~ 300 x 10-11
SUSY models – there are many – predict a contributions of about the observed magnitude for a These are rather well studied, so we will consider a few cases
The “Uninvented” – perhaps most importantly, sets a stringent experimental constraint for any new models
What kind of new physics?
D. Stockinger Note: a centered at 255 here
C depends on the modelNote: 42,000 more sensitive than electron
M(GeV)
13
SUSY contribution to aμ :
difficult to measure at LHC
Related processes in SUSY: Lepton Flavor Violation
MEG Mu2e & COMET
Connection between a, EDM and the charged Lepton Flavor Violating transition moment → e
→ e a (real) EDM (imaginary)
SUSY slepton mixing
Note: a centered at 255 here
SUSY and g-2: The power to resolve among models and break LHC degeneracies
16
Suppose the MSSM point SPS1a is realized and the parameters are determined at LHC- sgn( gives sgn()
• sgn () difficult to obtain from the collider• tan poorly determined by the collider
Assuming SPS1a; 100 fb-1 at 14 TeV
LHC (Sfitter)
Old g-2
New g-2
Build on a proven technique
Make use of unique storage ring
New team built from E821 experts, augmented by significant new strengths
Obtain more muons
Control systematic errors
Keys to an improved experiment:µ
1 ppm contours
Booster/Linac
Extraction from RR
Injection to RR
NEW TRANSFER LINE
A3 lineA2 line
Main Injector
F0P1 line
MI-52
MI-30
p
Recycler
_p
MI-10
Pbar
AP0
P2 line
Accelerator Overview
INJ8GeV
Ideal muon delivery to storage ring using the excess proton batches from neutrino program
Parasitic with program Shared infrastructure with Mu2e Uses existing p-bar target hall Ideal bunch structure Long decay beam lines optimal
Parameter FNAL/BNL
p / fill 0.25
/ p 0.4
survive to ring 0.01
at magic P 50
Net 0.05
The 900-m long decay beam: reduced flash; more store /p
Stored muons / POT
Parameter BNL FNAL Gain FNAL/BNL
Flash compared to BNL
4 Key elements of the BNL & FNAL g-2 measurement
(1) Polarized muons~97% polarized for forward decays
(2) Precession proportional to (g-2)
(3) P magic momentum = 3.094 GeV/cE field doesn’t affect muon spin when = 29.3
(4) Parity violation in the decay gives average spin direction
µ
EaBa
mce
a
1
12
ee
2
2a spin cyclotron
g eB
mc
20
The anomaly is obtained from three well-measured quantities
TIME
ap
The Storage Ring exists. It will be moved to FNAL
The Storage Ring components affect muon storage
incoming muons
Superconducting inflector magnet
Fast Kickers
Electrostatic Quadrupoles
The present inflector magnet has closed ends which scatter away ~half the incoming muon beam
Length = 1.7 m; Central field = 1.45 T
Open end prototype, built and tested
x2 increase in stored muons
As-used Closed-ended
Prototype Open-ended
Improvements in the kicker are planned because present one underkicks and pulse lasts too long.
This kick affects the storage efficiency
IDEAL kick 8%
REAL kick <3 %
149 ns cyclotron period
Kicker waveform
Kicker Amplitude
New tools allow us to simulate modified kicker pulse shapes and predict storage improvements
Real LCR Kick
Ideal Square Kick10
8
6
4
2
0
% stored
- p. 27/25
The ± 1 ppm uniformity in the average field is obtained with special shimming tools.
The
dipole,
quadrupole
sextupole
are shimmed independently
6 – 9 months required with cryogenics and ring on / off and in stable operating mode
Improvement of Field by Shimming
1999
2000
2001
shimming shimming
At this level, one hardly needs to know the muon distribution
Absolute Calibration Probe: a Spherical Water Sample
Electronics,Computer & Communication
Position ofNMR Probes
The magnetic field is measured and controlled using pulsed NMR and the free-induction decay
Fixed Probes in the walls of the vacuum tank
Trolley with matrix of 17 NMR Probes
An “event” is an isolated positron above a threshold.
e+
digitized samples
N
A
NA2
<A>=0.4
An “event” is an isolated positron above a threshold.
e+
digitized samples
Traditional method of determining a is to plot Number of events above threshold vs. Time
Event Method
Geant
N
A
NA2
<A>=0.4
Here, Asym is the average asymmetry of events above energy threshold cut
A complementary (integrating) method of determining a is to plot Energy vs. Time
Event Method
Geant
Energy Method
Same GEANT simulationWe will operate this mode in parallel to above
Parasitic Muon EDM Measurement using straw tube arrays
The EDM tips the precession plane, producing an up-down oscillation with time (out of phase with a)
BNL statistics limited 1 tracking station Late turn-on time Small acceptance Ran 2 out of 3 years
FNAL: many stations, long runs, expect ~10,000 x the events
Technique: Measure up-going/down-going tracks vs. time, (modulo g-2):
Detector systems
Calos: time and energy of decays Hodoscopes: beam profiles, calo
seeds, muon loss monitor In-vacuum Straws: stored muon profile
& independent EDM measurement
Hodoscope
hodoscope
CALO
e+
X
E821
Systematic error projections are in-line with statistical goal
Precession
Improvement vs time
Magnetic fie
ld
To here, requires “no” improvements. To 0.07 requires some R&D
The Ring Assembly
37
38
Sikorsky S64F 12.5 T hook weight (Outer coil 8T)
38
39
Status of the project …• March 09: Proposal presented
– PAC positive
– Committee to cost it
• Summer 09: Costing • Oct. 09: Cost verifications• Nov. 09: PAC revisits
– recommends Stage-1 approval
• Feb. 10: DOE Briefing– Invitation to compete as new project
• April 10: Proposal submitted to DOE• August 10: “Shootout” vs B factories
– EMBARGOED result for now
40
Summary
30x10-11
P-989
goal
16x10-11
FNAL
Future
15x10-11
Project X?
8x10-11
Proje
ct
X?
• The physics case for g-2 is stronger than ever
• Lots of room for new groups to join and make it happen
• The Fermilab Director is very optimistic about this happening
THEORY
g-2 provides a unique opportunity, which will have a lasting impact on our ability to understand what we find at the energy frontier
40
?
41
Backup …
SPS points and slopes SPS 1a: ``Typical '' mSUGRA point with intermediate value of tan_beta. SPS 1b: ``Typical '' mSUGRA point with relatively high tan_beta; tau-
rich neutralino and chargino decays. SPS 2: ``Focus point '' scenario in mSUGRA; relatively heavy squarks
and sleptons, charginos and neutralinos are fairly light; the gluino is lighter than the squarks
SPS 3: mSUGRA scenario with model line into ``co-annihilation region''; very small slepton-neutralino mass difference
SPS 4: mSUGRA scenario with large tan_beta; the couplings of A, H to b quarks and taus as well as the coupling of the charged Higgs to top and bottom are significantly enhanced in this scenario, resulting in particular in large associated production cross sections for the heavy Higgs bosons
SPS 5: mSUGRA scenario with relatively light scalar top quark; relatively low tan_beta
SPS 6: mSUGRA-like scenario with non-unified gaugino masses SPS 7: GMSB scenario with stau NLSP SPS 8: GMSB scenario with neutralino NLSP SPS 9: AMSB scenario
www.ippp.dur.ac.uk/~georg/sps/sps.html
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