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