B. Lee Roberts, PHIPSI 2009, Beijing – 14 October 2009 - p. 1/30 Status of the (g - 2) Fermilab Project Lee Roberts Department of Physics Boston University

B. Lee Roberts, PHIPSI 2009, Beijing – 14 October 2009 - p. 1/30

Status of the (g - 2) Fermilab Project

Lee RobertsDepartment of Physics

Boston Universityroberts @bu.edu

http://physics.bu.edu/show/roberts


New Collaborators are welcome! proposal is at http://lss.fnal.gov/archive/test-proposal/0000/fermilab-proposal-0989.shtml

http://lss.fnal.gov/archive/test-proposal/0000/fermilab-proposal-0989.shtml


• To understand where we’re going, you have to understand where we’ve been.

• Muons:– born polarized

– die with information on where their spin was at the time of decay

– highest energy e- carry spin information

Self-analyzing Muon Decay

N

A

NA2

<A>=0.4


Spin Motion: difference frequency between S and C

Count number of decay e- with Ee ≥ 1.8 GeV

0

Since g > 2, the spin gets ahead of the momentum

Dirac:

where a is the anomaly,


e± from ± → e± are detected

Count number of e- with Ee ≥ 1.8 GeV

400 MHz digitizer

gives t, E


• E821 at Brookhaven– superferric storage ring, magic , <B> ± 1 ppm

Our past a Experiment:

s

= 64.4 s; (g-2): a = 4.37 s; Cyclotron: tC = 149 ns


Pedestal vs. Time

Near side Far side

E821: used a “forward” decay beam with ≃ 1:1large “flash” in the detectors at injection

Pions @ 3.115 GeV/c

Decay muons @ 3.094 GeV/c

This baseline limits how early we can fit data

≃ 80 m decay path


The magnetic field is measured and controlled using pulsed NMR and the free-induction decay.

• Calibration to a spherical water sample that ties the field to the Larmor frequency of the free proton p.

• We measure a and p

• Use = /p as the “fundamental constant”


The ± 1 ppm uniformity in the average field is obtained with special shimming tools.

0.5 ppm contours


New value for (CODATA 2006/2008)(Rev. Mod. Phys. 80, 633 (2008))

Blind analysis


E821 achieved 0.54 ppm; e+e- based theory 0.49 ppm Hint is 3.2

Davier et al, arXiv:0908.4300 [hep-ph] n.b. the experimental point does not include the new value of

B. Lee Roberts, PHIPSI 2009, Beijing – 14 October 2009 - p. 12/30- p. 12/68

Model

UED

The Snowmass Points and Slopes give benchmarks to test observables with model predictions

Future?

Present

Muon g-2 is a powerful discriminator ...no matter where the final value lands!

SPSDefinitions


Suppose the MSSM point SPS1a is realized and the paramaters are determined at LHC- sgn( gives sgn()

LHC (Sfitter)

Old g-2

New g-2

• sgn () difficult to obtain from the collider• tan poorly determined by the collider

from D. Stöckinger

from Dominik Stöckinger


• E821 at Brookhaven– superferric storage ring, magic , <B> ± 1 ppm

• P989 at Fermilab– move the storage ring to Fermilab, improved shimming, new

detectors, electronics, DAQ, – new beam structure that takes advantage of the multiple

rings available at Fermilab, more muons per hour, less per fill of the ring

Fermilab a Experiment:


Advantages of the magic technique

• 3rd generation (CERN, E821, Fermilab)– technique well understood– high intensity polarized muon beam– large storage ring has ample room for detectors, field mapping,

etc.– muon injection shown to work– rates in detectors are “reasonable” with conventional technology

– many (g -2) cycles to fit over

– large decay asymmetry– precision field techniques well understood

• need to improve monitoring and control, but path is straightforward, if challenging.

– systematic errors well understood and can be improved

• Limit of this technique ≃0.07 to 0.1 ppm error


Why Fermilab?

• The existence of many storage rings that are interlinked permits us to make the “ideal” beam structure.– proton bunch structure:

• BNL ~5 X 1012 p/fill: effective rate 4.4 Hz• FNAL 1012 p/fill: effective rate 18 Hz

– using antiproton rings as an 900m pion decay line• 20 times less pion flash at injection than BNL

– 0o muons • ~5-10x increase /p over BNL

– Can run parasitic to main injector experiments (e.g. to NOVA) or take all the booster cycles


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

Polarized muons delivered and stored in the ring at the magic momentum, 3.094 GeV/c

Uses 6/20 batches* parasitic to program

Proton plan up to AP0 target is almost the same as for Mu2e

Uses the same target and lens as the present p-bar program

Modified AP2 line (+ quads) New beam stub into ring Needs simple building near

cryo services*Can use all 20 if MI program is off

beam rebunched in Recycler

4 x (1 x 1012) p


The 900-m long decay beam reduces the pion “flash” by x20 and leads to 6 – 12 times more stored muons per proton (compared to BNL)

Stored Muons / POT

Flash compared to BNL

parameter FNAL/BNL

p / fill 0.25

/ p 0.4

survive to ring 0.01

at magic P 50

Net 0.05


Building Design for Fermilab

AP0g-2


Stable 2.5’ thick reinforced floor, supported by 4’ diameter caissons down to bedrock; temperature controlled ± 2o F (Much better than E821)


Upgrades at Fermilab

• New segmented detectors to reduce pileup– W-scifi prototype under study

• New electronics– 500 MHz 12-bit WFDs, with deep memories

• Improvements in the magnetic field calibration, measurement and monitoring.


Complementary ways to collect data

Event Method

Geant simulation using new detector schemes

• “t” method – time and energy of each event - pileup


Complementary ways to collect data

Event Method

Geant simulation using new detector schemes

Energy Method

Same GEANT simulation

• “t” method – time and energy of each event - pileup

• “q” method – integrate the energy - no pileup


The error budget for a new experiment represents a continuation of improvements already made during E821

Systematic uncertainty (ppm) 1998 1999 2000 2001 E821 final

P989

Goal

Magnetic field – p 0.5 0.4 0.24 0.17 0.07

Anomalous precession – a 0.8 0.3 0.31 0.21 0.07

Statistical uncertainty (ppm) 4.9 1.3 0.62 0.66 0.46 0.1

Systematic uncertainty (ppm) 0.9 0.5 0.39 0.28 0.28 0.1

Total Uncertainty (ppm) 5.0 1.3 0.73 0.72 0.54 0.14


Systematic errors on ωa (ppm)

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 0.02

Timing Shifts 0.10 0.02 0.02

E-Field, Pitch 0.08 0.03 0.06* 0.03

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 0.02

total 0.3 0.31 0.21 ~0.07

Σ* = 0.11


The Precision Field: Systematic errors

• Why is the error 0.11 ppm?– That’s with existing knowledge and experience

• with R&D defined in proposal, it will get betterNext

(g-2)


Ring relocation to Fermilab

• Heavy-lift helicopters bring coils to a barge• Rest of magnet is a “kit” that can be trucked to and from the barge

Back


Sikorsky S64F 12.5 T hook weight (Outer coil 8T)

from Chris Polly


Possible Schedule?

• CY 2009– PAC proposal defended in March 2009 (Well received, but how many$?)– Laboratory supports costing exercise July-October– Report to PAC meeting November

• CY 2010 Approval?– building design finished– other preliminary engineering and R&D

• CY 2011 Tevatron running finishes in Oct. – building construction begins– ring disassembly begins FY2012

• CY 2012 – building completed mid-year– ring shipped

• 2013-2014– re-construct ring– shim magnet

• late 2014 or early 2015 Beam to experiment – 2 year data collection on +


• At present there appears to be a difference between a and the standard-model e+e- based prediction at the 3.2 level, post BaBar.

• We have proposed to reduce the experimental error by a factor of 4 at Fermilab.

• Our goal is to clarify if there is a discrepancy between experiment and theory, but whatever happens a will continue to be valuable in restricting physics beyond the standard model.

• It will be especially important in guiding the interpretation of the LHC data.

Summary


A special thank you to our hosts!

THE END


muon (g-2) storage ring

Muon lifetime tm = 64.4 ms

(g-2) period ta = 4.37 ms

Cyclotron period tC = 149 ns


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.htmlSPS PLOT

Back


(g-2) at Fermilab: Costing study concluding this month.

Coils have to be moved by helicopter and barge


a Systematic Error Summary


New value for (CODATA 2006/2008)(Rev. Mod. Phys. 80, 633 (2008))

an increase by 14% of the experimental error

Documents

B. Lee Roberts, PHIPSI 2009, Beijing – 14 October 2009 - p. 1/30 Status of the (g - 2) Fermilab Project Lee Roberts Department of Physics Boston University