B. Lee Roberts

Lepton Photon 99

Boston University

10 August 1999

or

78 Years of Lepton-Photon Physics

x x

xx

Recent Results from theMuon (g-2) Experiment

xx

xx

Otto Stern and W. GerlachAnnalen der Physik, 74, 673 (1924)

Otto Stern, Z. Phys. 7, 249 (1921)

Lepton-Photon Physics began in 1921

Magnetic Moments, g factors, etc.

~�s = gs

� e2m

�~s

If �e = 1 Bohr Magneton, gs = 2.

γ

µ

γ

µγ

απ+

Schwinger, 1947Kusch and Foley,

g = 2

� = (1 + a)e�h

2m

where

a =

�g � 2

2

�

THEORETICAL VALUE FOR (g � 2)

Electron:

a�(Standard Model) = a� (QED) to 4ppb

Muon:

Relative Contribution of heavier things : �

�m�

me

�2

a�(SM) = a� (QED) + a� (hadronic) + a� (weak)

a�(New Physics) = a�(Measured)� a�(SM)

QED Contribution

a�(QED) = C1��

�

�+C2

��

�

�2+C3

��

�

�3+C4

��

�

�4+

C5

��

�

�5Taking the value of � from the electron (g�2), T. Kinoshita,

Rep. Prog. Phys. 59, 1459 (1996), yields the total QED value

a� (QED) = 116 584 705:7 (1:8) (0:5)�10�11 (�16ppb)

γ

µγ

απin

Higher Order Terms+

α2π

=

First Order Hadronic Contribution

����������

����������µhγ

γ

Determined experimentally from e+e� ! Hadronsor using hadronic � decays (assuming CVC, isospin

conservation and the absence of 2nd class currents)

h

+e

-e

γ -ττ

W-

ν

h

a� (had; 1) =��m�

3�

�2Z1

4m2�

ds

s2K (s)R (s)

Values of 1stOrder Hadronic Contribution

+ −e ,(e τ)

+ −(e e )

a µ * 1011

(had;1)

+ - τ(e e , , theory)

Bro.-Wor.

Eid.-Jeg .

Kin.-Niz.-Oka.

ADH

Al.-Dav.-Hoc.

DH

75007000

DH

a� (had; 1) = 7011 (94)�10�11 (60:13� 0:81) ppm

R. Alemany, M. Davier, A. Hocker, Eur.Phys.J. 2C (1998)123.

a� (had; 1) = 6951 (75)�10�11 (59:62� 0:64) ppm

M. Davier and A. Hocker, Phys. Lett. 419 (1998) 419.

a� (had; 1) = 6924 (62)�10�11 (59:39� 0:53) ppm

M. Davier and A. Hocker, Phys. Lett. 435 (1998) 427.

Higher Order Hadronic Contribution

-e

X-11

-101 (6) 10

��������

��������

������

������

��������

��������

����������

����������

+e

µ

γ

h

µ

h h

γ

µ

h

γ

Bernd Krause, Phys. Lett. B 390 (1997) 392

Hadronic Light-on-Light Contribution

���������������������������������������������������������������������������������������������������������������������������������������

���������������������������������������������������������������������������������������������������������������������������������������

X32-11

-85 ( ) 10

��������������������������������������������������������������������������������������������

µ

γ

γ

h

M. Hayakawa and T. Kinoshita, Phys. Rev. D57 (1998) 465and J. Bijnens, E. Pallante and J. Prades, Nucl. Phys. B474(1996) 379.

The Total Hadronic Contribution

a� (had; 1 + 2 + lol) = 6738 (70)�10�11 (57:79� 0:60)

Weak Contribution

µνµ

W W

γ

(a) (b)

µ

γ

Z0

µ

γ

Z0

f

f-

µW

νµ νµ

γ

µ

γ G

W G

H

γ

(c) (d) (e)

+389 -194

+ many other 2nd order diagrams

bosonicfermionic

2nd order

1st order

a� (weak; 1) = 195� 10�11 (1:7) ppm

a� (weak; 1 + 2) = 151 (4)�10�11 (1:30� 0:03) ppm

A. Czarnecki, B. Krause and W.J. Marciano, Phys. Rev. D52

(1995) R2619 and Phys. Rev. Lett. 76 (1996) 3267

Summary

Theoretical and Experimental Information

a� (QED) = 1 165 847 05:7 (2)�10�11 (�17 ppb)

a� (had) = 6738 (70)� 10�11 (57:79� 0:60) ppm

a� (weak) = 151 (4)� 10�11 (1:30� 0:03) ppm

The Total Standard Model Value of a� is

a� (SM) = (116 591 594:7 � 70)�10�11 (�0:60 ppm)

The experimental value is

a� (exp) = (116 592 350 � 730)�10�11 (�6:3 ppm)

or

a� (exp)� a� (theory) = (755� 733)� 10�11

E821 goal: � 40�10�11 or � 0:35 ppm

(g � 2) is Sensitive to New Physics

If �a� = 0:35 ppm then:

MUON SUBSTRUCTURE

�a� �m

2�

�2� � 5 TeV LHC domain

WCOMPOSITENESS/ANOMALOUS COUPLINGS

� � 400 GeV LEPII � 100� 200 GeV

�W =e

2mW(1 + �+ �)

a� (�; �) 'GFm

2�

4p2�2

"(�� 1) ln �

2

m2

W

� 13�

#

Bounds

F

ure

ut

2W2Wy = f

M2Λ

2W2Bx = f

M2Λ

????????????????????????????????????????

????????????????????????????????????????????

????????????????

-0.2

b

LEP2

+(g-2)

-0.1

0

-0.1

-0.2

-0.4 0 0.4 0.8 1.2

+R (LEP1)Λ = 1 TeV∆κ = x+yγ∆κ =κ −1γγ

(1997) 398

Renard, et al.PL B409

SUPER SYMMETRY (SUSY)

∼µ ∼+

γ

0χµµ

µ

ν∼

−− χ µµ

γ

χ

a� is sensitive to any SUSY model with largetan�

If tan� >> 1 the �� ~� diagram dominates.For large tan�:

a� (SUSY) '�

8� sin2 �W

m2�

~m2tan�

' 140� 10�11�100 GeV

~m

�2

tan�

(1:23 ppm)

If ~m = 750 GeV and tan� = 40 then:

a� (SUSY) = 100� 10�11

� BNL Goal is � 40 � 10�11 (� 0:35 ppm)

� (g � 2)� already improves LEP2 bounds.

� If ~� is light, chargino production is supressed.

� If the chargino is only slightly heavier than

the ~�, the decay products are hard to de-

tect.

Current E821 Collaboration

R.M. Carey, W. Earle, E. Efstathiadis, M. Hare, E.S. Hazen,

F. Krienen, J.P. Miller, J. Paley, O. Rind, B.L. Roberts, L.R.

Sulak, A. Tro�mov, - Boston University

H.N. Brown, G. Bunce, G.T. Danby, M. Grosse-Perdekamp, R.

Larsen, Y.Y. Lee, W. Meng, J.-L. Mi, W.M. Morse, C. Ozben,

C. Pai, R. Prigl, R. Sanders, Y.K. Semertzidis, D. Warburton

- Brookhaven National Laboratory

Y. Orlov - Cornell University

D. Winn - Fair�eld University

A. Grossmann, K. Jungmann, I. Rheinhardt, G. zu Putlitz -

University of Heidelberg

P.T. Debevec, W. Deninger, F. Gray, D.W. Hertzog, C.J.G.

Onderwater, C. Polly, S. Sedyk, M. Sossong, D. Urner - Uni-

versity of Illinois

U. Haeberlen -Max Planck Institiute fur Med. Forschung,

Heidelberg

P. Cushman, L. Duong, S. Giron, J. Kindem, I. Kronkvist,

R. McNabb, D. Miller, C. Timmermans, D. Zimmerman -

University of Minnesota

V.P. Druzhinin, G.V. Fedotovich, B.I. Khazin, I. Logashenko,

N.M. Ryskulov, S. Serednyakov, Yu.M. Shatunov, E. Solodov

- Budker Institute of Nuclear Physics, Novosibirsk

A. Yamamoto - KEK

M. Iwasaki, M. Kawamura - Tokyo Institute of Technology

H. Deng, S.K. Dhawan, F.J.M. Farley, V.W. Hughes, D. Kawall,

J. Pretz, S.I. Redin, A. Steinmetz - Yale University

The Technique

� Use the AGS to make a 3.1 GeV � beam.� 115 m beamline choose � or � at a momentumslit and bring the � or � beam through aniron-free Superconducting Inector.

� Store ~� in Ring by a kick, � spin motion:

~!a =d�Rdt

=e

mc

�a� ~B �

�a� �

1

2 � 1

�~� � ~E

�

for magic

�a� �

1

2 � 1

�= 0

= 29:3 and p� = 3:094 GeV/c.

= emcω aaµB

Momentum Spin

� Count High Energy Electrons, Ee � 1:5 GeV,from

�+! e+ + ��� + �eas a Function of Time.

� Fit Time Spectrum to

N (t) = N0e�t=� [1�A cos (!at+ �)]

to determine the (g � 2) frequency

�" =�!a

!a=

p2

2�fa��N1

2A

t t

-t /e γτ

cos tω

t (µs)0 10 20 30 40 50 60 70 80 90 100

coun

ts /

500n

s

102

103

104

105

106 45-100

100-200

200-300

300-400

400-500

500-600

600-700

700-735

N (t) = N0e�t=� [1�A cos (!at+ �)]

E > 1.8 GeV, 357 X 10 e 6A Sample of the 1999 Data:

-5-4-3-2-1012345

-4 -2 0 2 4x [cm]

y [c

m]

0

-10ppm

10ppm

July 1997 field map

-5-4-3-2-1012345

-4 -2 0 2 4x [cm]

y [c

m]

-2ppm

2ppm

August 1998 field map

1 m

edge shims

wedges

R = 711.2 cm

r = 4.5 cm

2 ppm contours

CERN B Field

Muon (g-2) Storage Ring and B FieldX

B = 1.4513 T0

200 600400 800 1000

Kic

ker

Cur

rent

(kA

)

time (ns)

Kicker Current

Beam4

0

2

Kickers

Beamline

Inflector

x

xx

x

Parameter Value Comments

(g-2) Frequency fa � 0:23� 106=s !a = 2�fa

�a = 4:37�sMuon Lifetime � = 64:4 �sMuon kinematics p� = 3:094 GeV/c

� = 29:3Cyclotron Period �cyc = 149 nsCentral Radius � = 7112 mm (28000)Magnetic Field B = 1:451 TStorage Aperture 9:0 cm circleIn one lifetime: 432 revolutions around ring

14.7 (g-2) periods

Brookhaven E821 Muon Storage Ring

muon momentum

muon spinSci-Fi calorimeter

module

0 1 2 3

SELECTED BY GEOMETRY

ALL ELECTRONS

ON LINE OFFLINE

NU

MB

ER

OF

EL

EC

TR

ON

S

E (GeV)

ELECTRON ENERGY SPECTRA

Shape of the ring vacuum chamber is designed tooptimize the decay electron detection.

High energy electrons carry largest Asymmetry

= emcω aaµB

ω p

ω aω p

R =

ω aFit decay electron (positron) spectrum for ω aRemove offsets and divide to determine

Calibrate plunging probe to sperical H O probe.2

B (weighted)ω p B Track with 366 fixed NMR Probes,

ω pDetermine and thus . Weight with the muon distribution. (B) ω p

< B >=

ZV

M (r)B (r) d3r

Data Analysis (Done blind):

Calibrate trolley probes with plunging probe.Map field periodically with trolley.

,

x x

x x

Data VolumeData Volume

● Number of measured positrons withEnergy > 1.8 GeV.

3 0 140 4504 5 140 8205 10 12846 19007 2100

0

500

1000

1500

2000

1 2 3 4 5 6 7

Week

Mill

ion 97 pi eng

98 mu eng99 mu phy

CERNCERN

Results and Projections

(1997 Data) R =!a

!p

= 3:707 220 (47) (11)

a� =R

��R� =

��

�p

= 3:183 345 47 (47)

a� (E821) = (116 592 501� 1516)�10�11 (�13 ppm)

�BNL &

CERN

�= (116 592 344� 730)�10�11 (�6:3 ppm)

(6.3

ppm

)<

CE

RN

+E

821>

X 10

a

11µ

projected errors with current value*

116 593 000

-

E82

1 (9

7)

+ µµ −

(10

ppm

)

(10

ppm

)

µ+

(13

ppm

)

(~ 4

ppm

)

*

CE

RN

CE

RN

Futu

re G

oal

On

Tap

e

Theory

1998

Dat

a

E82

1 G

oal (

0.35

)

1999

~ +

1 p

pm

* *

New

Ave

rage*

Com

ing

Soon

(~ 5

.2 p

pm)

116 595 000

116 594 000

116 592 000

116 591 000

116 590 000

Systematic Errors

1997 Data:

Systematic error = �2:9 ppm (13 ppm total error)

� (< B >�) were 1.0 and 0.9ppm.

!p B-Field Related Errors from 1997, and projectederrors for 1998 and 2000

1997 1998 Est 2000 Est

(ppm) (ppm) (ppm)

!p 1 0.5 0.1 - 0.25

< !p >� 0.9 0.2-0.3 0.1

A 5 ppm result will come soon.

A 1 ppm result should come next year.

The systematic errors are continuing todecrease faster than then statistical errors.

production / running phase.The ( ) Experiment has entered the

x x

xx

g-2

Conclusions: