B. Lee Roberts, BNL PAC 9 September 2004 - p. 1 /29 Muon (g-2) to 0.20 ppm P969 B. Lee Roberts Representing the new g-2 collaboration: Boston, BNL, BINP, Cornell, Illinois, James Madison, Kentucky, KVI-Groningen, LBL&UC-Berkeley, Minnesota, Yale [email protected]http://physics.bu.edu/roberts.html
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B. Lee Roberts, BNL PAC 9 September 2004 - p. 1/29 Muon (g-2) to 0.20 ppm P969 B. Lee Roberts Representing the new g-2 collaboration: Boston, BNL, BINP,
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B. Lee Roberts, BNL PAC 9 September 2004 - p. 1/29
Muon (g-2) to 0.20 ppm
P969
B. Lee RobertsRepresenting the new g-2 collaboration:
B. Lee Roberts, BNL PAC 9 September 2004 - p. 2/29
This is a new collaboration built on the foundation of E821
• Core of our expertise from E821 remains
• New institutes have joined and we are actively recruiting additional collaborators
• Our precision storage ring remains the centerpiece of the experiment
B. Lee Roberts, BNL PAC 9 September 2004 - p. 3/29
Standard Model Value for (g-2)from virtual radiative processes
B. Lee Roberts, BNL PAC 9 September 2004 - p. 4/29
Ongoing worldwide effort to improve knowledge of …
• Lowest order hadronic contribution• Hadronic light-by-light
B. Lee Roberts, BNL PAC 9 September 2004 - p. 5/29
1st-order hadronic from e+e- annihilation and decay
B. Lee Roberts, BNL PAC 9 September 2004 - p. 6/29
Update: August 2004 (ICHEP)
• Precise e+e-and data are incompatible ... especially at energies above the
• New KLOE data using radiative return support the CMD2 e+e- data
• Isospin correction issues for the data remain unresolved
B. Lee Roberts, BNL PAC 9 September 2004 - p. 7/29
• Comparison with CMD-2 in the Energy Range 0.37 <s<0.93 GeV2
(375.6 0.8stat 4.9syst+theo) 10-10
(378.6 2.7stat 2.3syst+theo) 10-10
KLOECMD2
1.3% Error0.9% Error
a= (388.7 0.8stat 3.5syst
3.5theo) 10-10
2 contribution to ahadr
• KLOE has evaluated the Dispersions Integral for the 2-Pion-Channel in the Energy Range 0.35 <s<0.95 GeV2
• At large values of s (>m) KLOE is consistent with CMD and therefore
They confirm the deviation from -data!.
Pion Formfactor
CMD-2KLOE
0.4 0.5 0.6 0.7 0.8 0.9
s [GeV2]
45
40
35
30
25
20
15
10
5
45
0
KLOE, CMD2 Data on R(s)
Courtesy of G. Venanzone
B. Lee Roberts, BNL PAC 9 September 2004 - p. 8/29
A. Höcker at ICHEP04
B. Lee Roberts, BNL PAC 9 September 2004 - p. 9/29
aμ is sensitive to a wide range of new physics
• muon substructure
• anomalous couplings• SUSY (with large tanβ )
• many other things (extra dimensions, etc.)
B. Lee Roberts, BNL PAC 9 September 2004 - p. 10/29
Where we came from:
B. Lee Roberts, BNL PAC 9 September 2004 - p. 11/29
Today with e+e- based theory:
All E821 results were obtained with a “blind” analysis.
B. Lee Roberts, BNL PAC 9 September 2004 - p. 12/29
Discrepancy with e+e- based theory
• What might this mean?
• New physics or a fluctuation?– Consider a SUSY example
B. Lee Roberts, BNL PAC 9 September 2004 - p. 13/29
Courtesy K.Olivebased on Ellis, Olive, Santoso, Spanos
In CMSSM, a can be combined with b s, cosmological relic density h2, and LEP Higgs searches to constrain mass
Allowedband a(exp) – a(e+e- thy)
Excluded by direct searches
Excluded for neutral dark matter
Preferred
B. Lee Roberts, BNL PAC 9 September 2004 - p. 14/29
Current Discrepancy Standard Model
The CMSSM plot with error on aof 4.6 x 10-10
(assuming better theory and a new BNL g-2 experiment)
a=24(4.6) x 10-10 (discrepancy at 6 a0 (4.6) x 10-
10
B. Lee Roberts, BNL PAC 9 September 2004 - p. 15/29
Discrepancy with e+e- based theory
• What might this mean?
• New physics or a fluctuation?– Consider a SUSY example
• Either way, the muon (g-2) provides a wonderful test of the standard model
B. Lee Roberts, BNL PAC 9 September 2004 - p. 16/29
With a discrepancy like this…
• You’ve got to keep working– Either you confirm the discrepancy or– You show it’s not there…
• But you can’t ignore it! – The stakes are just too high.
• That’s why we’re here today.
B. Lee Roberts, BNL PAC 9 September 2004 - p. 17/29
The experimental concept remains the same:
B. Lee Roberts, BNL PAC 9 September 2004 - p. 18/29
And so does the ring
B. Lee Roberts, BNL PAC 9 September 2004 - p. 19/29
Strategy of the improved experiment
• More muons – E821 was statistics limited stat = 0.46 ppm, syst = 0.3 ppm– Backward-decay, higher-transmission beamline– New, open-end inflector – Upgrade detectors, electronics, DAQ
• Improve knowledge of magnetic field B– Improve calibration, field monitoring and measurement
• Reduce systematic errors on ωa
– Improve the electronics and detectors – New parallel “integration” method of analysis
B. Lee Roberts, BNL PAC 9 September 2004 - p. 20/29
E821: Forward decay beam
Pions @ 3.115 GeV/c
Decay muons @ 3.094 GeV/c
Pedestal vs. Time
Near side Far side
B. Lee Roberts, BNL PAC 9 September 2004 - p. 21/29
P969: Backward decay beam
Expect for both sides
Pions @ 5.32 GeV/c
Decay muons @ 3.094 GeV/c
No hadron-induced prompt flash
Approximately the same muon flux is realized
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Muon capture and transmission in decay section will double by doubling quads
Lattice doubled
E821 lattice
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Improved transmission into the ring
InflectorInflector aperture
Storage ring aperture
E821 Closed End P969 Proposed Open End
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Systematic Error Evolution
• 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