x x recent results from the muon (g-2) experiment · x x x x otto stern and w. gerlach annalen der...
TRANSCRIPT
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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
�
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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
=
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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.
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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)
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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
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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
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(g � 2) is Sensitive to New Physics
If �a� = 0:35 ppm then:
MUON SUBSTRUCTURE
�a� �m
2�
�2� � 5 TeV LHC domain
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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
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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.
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� If ~� is light, chargino production is supressed.
� If the chargino is only slightly heavier than
the ~�, the decay products are hard to de-
tect.
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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
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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
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� 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
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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
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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: